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Kim YJ, Mendes JL, Michelsen JM, Shin HJ, Lee N, Choi YJ, Cushing SK. Coherent charge hopping suppresses photoexcited small polarons in ErFeO 3 by antiadiabatic formation mechanism. Sci Adv 2024; 10:eadk4282. [PMID: 38507483 PMCID: PMC10954221 DOI: 10.1126/sciadv.adk4282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 02/13/2024] [Indexed: 03/22/2024]
Abstract
Polarons are prevalent in condensed matter systems with strong electron-phonon coupling. The adiabaticity of the polaron relates to its transport properties and spatial extent. To date, only adiabatic small polaron formation has been measured following photoexcitation. The lattice reorganization energy is large enough that the first electron-optical phonon scattering event creates a small polaron without requiring substantial carrier thermalization. We measure that frustrating the iron-centered octahedra in the rare-earth orthoferrite ErFeO3 leads to antiadiabatic polaron formation. Coherent charge hopping between neighboring Fe3+─Fe2+ sites is measured with transient extreme ultraviolet spectroscopy and lasts several picoseconds before the polaron forms. The resulting small polaron formation time is an order of magnitude longer than previous measurements and indicates a shallow potential well, even in the excited state. The results emphasize the importance of considering dynamic electron-electron correlations, not just electron-phonon-induced lattice changes, for small polarons for transport, catalysis, and photoexcited applications.
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Affiliation(s)
- Ye-Jin Kim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jocelyn L. Mendes
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jonathan M. Michelsen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Hyun Jun Shin
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Nara Lee
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Young Jai Choi
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Scott K. Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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He M, Hickam BP, Harper N, Cushing SK. Experimental upper bounds for resonance-enhanced entangled two-photon absorption cross section of indocyanine green. J Chem Phys 2024; 160:094305. [PMID: 38445732 DOI: 10.1063/5.0193311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 02/15/2024] [Indexed: 03/07/2024] Open
Abstract
Resonant intermediate states have been proposed to increase the efficiency of entangled two-photon absorption (ETPA). Although resonance-enhanced ETPA (r-ETPA) has been demonstrated in atomic systems using bright squeezed vacuum, it has not been studied in organic molecules. We investigate for the first time r-ETPA in an organic molecular dye, indocyanine green (ICG), when excited by broadband entangled photons in near-IR. Similar to many reported virtual state mediated ETPA (v-ETPA) measurements, no r-ETPA signals are measured, with an experimental upper bound for the cross section placed at 6(±2) × 10-23 cm2. In addition, the classical resonance-enhanced two-photon absorption (r-TPA) cross section of ICG at 800 nm is measured for the first time to be 20(±13) GM, where 1 GM equals 10-50 cm4 s, suggesting that having a resonant intermediate state does not significantly enhance two-photon processes in ICG. The spectrotemporally resolved emission signatures of ICG excited by entangled photons are also presented to support this conclusion.
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Affiliation(s)
- Manni He
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Bryce P Hickam
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Nathan Harper
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Scott K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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3
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Kim YJ, Palmer LD, Lee W, Heller NJ, Cushing SK. Using electron energy-loss spectroscopy to measure nanoscale electronic and vibrational dynamics in a TEM. J Chem Phys 2023; 159:050901. [PMID: 37526153 DOI: 10.1063/5.0147356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 05/22/2023] [Indexed: 08/02/2023] Open
Abstract
Electron energy-loss spectroscopy (EELS) can measure similar information to x-ray, UV-Vis, and IR spectroscopies but with atomic resolution and increased scattering cross-sections. Recent advances in electron monochromators have expanded EELS capabilities from chemical identification to the realms of synchrotron-level core-loss measurements and to low-loss, 10-100 meV excitations, such as phonons, excitons, and valence structures. EELS measurements are easily correlated with electron diffraction and atomic-scale real-space imaging in a transmission electron microscope (TEM) to provide detailed local pictures of quasiparticle and bonding states. This perspective provides an overview of existing high-resolution EELS (HR-EELS) capabilities while also motivating the powerful next step in the field-ultrafast EELS in a TEM. Ultrafast EELS aims to combine atomic-level, element-specific, and correlated temporal measurements to better understand spatially specific excited-state phenomena. Ultrafast EELS measurements also add to the abilities of steady-state HR-EELS by being able to image the electromagnetic field and use electrons to excite photon-forbidden and momentum-specific transitions. We discuss the technical challenges ultrafast HR-EELS currently faces, as well as how integration with in situ and cryo measurements could expand the technique to new systems of interest, especially molecular and biological samples.
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Affiliation(s)
- Ye-Jin Kim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Levi D Palmer
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Wonseok Lee
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Nicholas J Heller
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - Scott K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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Harper N, Hickam BP, He M, Cushing SK. Entangled Photon Correlations Allow a Continuous-Wave Laser Diode to Measure Single-Photon, Time-Resolved Fluorescence. J Phys Chem Lett 2023:5805-5811. [PMID: 37338128 DOI: 10.1021/acs.jpclett.3c01266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2023]
Abstract
Fluorescence lifetime experiments are a standard approach for measuring excited-state dynamics and local environmental effects. Here, we show that entangled photon pairs produced from a continuous-wave (CW) laser diode can replicate pulsed laser experiments without phase modulation. As a proof of principle, picosecond fluorescence lifetimes of indocyanine green are measured in multiple environments. The use of entangled photons has three unique advantages. First, low-power CW laser diodes and entangled photon source design lead to straightforward on-chip integration for a direct path to distributable fluorescence lifetime measurements. Second, the entangled pair's wavelength is easily tuned by adjusting the temperature or electric field, allowing a single source to cover octave bandwidths. Third, femtosecond temporal resolutions can be reached without requiring major advances in source technology or external phase modulation. Entangled photons could therefore provide increased accessibility to time-resolved fluorescence while also opening new scientific avenues in photosensitive and inherently quantum systems.
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Affiliation(s)
- Nathan Harper
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - Bryce P Hickam
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - Manni He
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
| | - Scott K Cushing
- Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd., Pasadena, California 91125, United States
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Liu H, Michelsen JM, Mendes JL, Klein IM, Bauers SR, Evans JM, Zakutayev A, Cushing SK. Measuring Photoexcited Electron and Hole Dynamics in ZnTe and Modeling Excited State Core-Valence Effects in Transient Extreme Ultraviolet Reflection Spectroscopy. J Phys Chem Lett 2023; 14:2106-2111. [PMID: 36802601 DOI: 10.1021/acs.jpclett.2c03894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Transient extreme ultraviolet (XUV) spectroscopy is becoming a valuable tool for characterizing solar energy materials because it can separate photoexcited electron and hole dynamics with element specificity. Here, we use surface-sensitive femtosecond XUV reflection spectroscopy to separately measure photoexcited electron, hole, and band gap dynamics of ZnTe, a promising photocathode for CO2 reduction. We develop an ab initio theoretical framework based on density functional theory and the Bethe-Salpeter equation to robustly assign the complex transient XUV spectra to the material's electronic states. Applying this framework, we identify the relaxation pathways and quantify their time scales in photoexcited ZnTe, including subpicosecond hot electron and hole thermalization, surface carrier diffusion, ultrafast band gap renormalization, and evidence of acoustic phonon oscillations.
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Affiliation(s)
- Hanzhe Liu
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
- Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, United States
| | - Jonathan M Michelsen
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jocelyn L Mendes
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Isabel M Klein
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Sage R Bauers
- Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Jake M Evans
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Andriy Zakutayev
- Materials Science Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Scott K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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Hickam BP, He M, Harper N, Szoke S, Cushing SK. Single-Photon Scattering Can Account for the Discrepancies among Entangled Two-Photon Measurement Techniques. J Phys Chem Lett 2022; 13:4934-4940. [PMID: 35635002 DOI: 10.1021/acs.jpclett.2c00865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Entangled photon pairs are predicted to linearize and increase the efficiency of two-photon absorption, allowing continuous wave laser diodes to drive ultrafast time-resolved spectroscopy and nonlinear processes. Despite a range of theoretical studies and experimental measurements, inconsistencies in the value of the entanglement-enhanced interaction cross section persist. A spectrometer that can temporally and spectrally characterize the entangled photon state before, during, and after any potential two-photon excitation event is constructed. For the molecule rhodamine 6G, which has a virtual state pathway, any entangled two-photon interaction is found to be equal to or weaker than classical, single-photon scattering events. This result can account for the discrepancies among the wide variety of entangled two-photon absorption cross sections reported from different measurement techniques. The reported instrumentation can unambiguously separate classical and entangled effects and therefore is important for the growing field of nonlinear and multiphoton entangled spectroscopy.
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Affiliation(s)
- Bryce P Hickam
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Manni He
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Nathan Harper
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Szilard Szoke
- Division of Engineering and Applied Science, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
| | - Scott K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, Pasadena, California 91125, United States
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Szoke S, He M, Hickam BP, Cushing SK. Designing high-power, octave spanning entangled photon sources for quantum spectroscopy. J Chem Phys 2021; 154:244201. [PMID: 34241348 DOI: 10.1063/5.0053688] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Entangled photon spectroscopy is a nascent field that has important implications for measurement and imaging across chemical, biology, and materials fields. Entangled photon spectroscopy potentially offers improved spatial and temporal-frequency resolutions, increased cross sections for multiphoton and nonlinear measurements, and new abilities in inducing or measuring quantum correlations. A critical step in enabling entangled photon spectroscopies is the creation of high-flux entangled sources that can use conventional detectors as well as provide redundancy for the losses in realistic samples. Here, we report a periodically poled, chirped, lithium tantalate platform that generates entangled photon pairs with ∼10-7 efficiency. For a near watt level diode laser, this results in a near μW-level flux. The single photon per mode limit that is necessary to maintain non-classical photon behavior is still satisfied by distributing this power over up to an octave-spanning bandwidth. The spectral-temporal photon correlations are observed via a Michelson-type interferometer that measures the broadband Hong-Ou-Mandel two-photon interference. A coherence time of 245 fs for a 10 nm bandwidth in the collinear case and a coherence time of 62 fs for a 125 nm bandwidth in the non-collinear case are measured using a CW pump laser and, essentially, collecting the full photon cone. We outline in detail the numerical methods used for designing and tailoring the entangled photons source, such as changing center wavelength or bandwidth, with the ultimate aim of increasing the availability of high-flux UV-Vis entangled photon sources in the optical spectroscopy community.
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Affiliation(s)
- S Szoke
- Division of Engineering and Applied Sciences, California Institute of Technology, Pasadena, California 91125, USA
| | - M He
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - B P Hickam
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | - S K Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
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Abstract
The chemical and electromagnetic (EM) enhancements both contribute to surface-enhanced Raman scattering (SERS). It is well-known that the EM enhancement is induced by the intense local field of surface plasmon resonance (SPR). This report shows that the polarizability of the molecules adsorbed on the metal surface can lead to another channel for the EM field enhancement. When aromatic molecules are covalently bonded to the Au surface, they strongly interact with the plasmon, leading to a modification of the absorption spectrum and a strong SERS signal. The effect is seen in both 3 nm-Au nanoparticles with a weak SPR and 15 nm-Au nanoparticles with a strong SPR, suggesting that the coupling is through both EM field and chemical means. Linear-chain molecules on the 3 nm-Au nanoparticles do not have a SERS signal. However, when the aromatic and linear molecules are co-adsorbed, the strong SPR/molecular polarizability interaction spatially extends the local EM field, leading to a strong SERS signal from the linear-chain molecules. The results show that aromatic molecules immobilized on Au can create "hot spots" just like plasmonic nanostructures.
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Affiliation(s)
- Ming Li
- School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083, China and Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
| | - Scott K Cushing
- Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Guangwen Zhou
- Department of Mechanical Engineering and Multidisciplinary Program in Materials Science and Engineering, State University of New York, Binghamton, New York 13902, USA
| | - Nianqiang Wu
- Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, MA 01003-9303, USA. and Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
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9
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Cushing SK, Porter IJ, de Roulet BR, Lee A, Marsh BM, Szoke S, Vaida ME, Leone SR. Layer-resolved ultrafast extreme ultraviolet measurement of hole transport in a Ni-TiO 2-Si photoanode. Sci Adv 2020; 6:eaay6650. [PMID: 32284972 PMCID: PMC7124930 DOI: 10.1126/sciadv.aay6650] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 01/08/2020] [Indexed: 05/30/2023]
Abstract
Metal oxide semiconductor junctions are central to most electronic and optoelectronic devices, but ultrafast measurements of carrier transport have been limited to device-average measurements. Here, charge transport and recombination kinetics in each layer of a Ni-TiO2-Si junction is measured using the element specificity of broadband extreme ultraviolet (XUV) ultrafast pulses. After silicon photoexcitation, holes are inferred to transport from Si to Ni ballistically in ~100 fs, resulting in characteristic spectral shifts in the XUV edges. Meanwhile, the electrons remain on Si. After picoseconds, the transient hole population on Ni is observed to back-diffuse through the TiO2, shifting the Ti spectrum to a higher oxidation state, followed by electron-hole recombination at the Si-TiO2 interface and in the Si bulk. Electrical properties, such as the hole diffusion constant in TiO2 and the initial hole mobility in Si, are fit from these transient spectra and match well with values reported previously.
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Affiliation(s)
- Scott K. Cushing
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Ilana J. Porter
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Bethany R. de Roulet
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Angela Lee
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Brett M. Marsh
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Szilard Szoke
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Mihai E. Vaida
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
| | - Stephen R. Leone
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA
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Cushing SK, Zürch M, Kraus PM, Carneiro LM, Lee A, Chang HT, Kaplan CJ, Leone SR. Hot phonon and carrier relaxation in Si(100) determined by transient extreme ultraviolet spectroscopy. Struct Dyn 2018; 5:054302. [PMID: 30246050 PMCID: PMC6133686 DOI: 10.1063/1.5038015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/22/2018] [Indexed: 05/16/2023]
Abstract
The thermalization of hot carriers and phonons gives direct insight into the scattering processes that mediate electrical and thermal transport. Obtaining the scattering rates for both hot carriers and phonons currently requires multiple measurements with incommensurate timescales. Here, transient extreme-ultraviolet (XUV) spectroscopy on the silicon 2p core level at 100 eV is used to measure hot carrier and phonon thermalization in Si(100) from tens of femtoseconds to 200 ps, following photoexcitation of the indirect transition to the Δ valley at 800 nm. The ground state XUV spectrum is first theoretically predicted using a combination of a single plasmon pole model and the Bethe-Salpeter equation with density functional theory. The excited state spectrum is predicted by incorporating the electronic effects of photo-induced state-filling, broadening, and band-gap renormalization into the ground state XUV spectrum. A time-dependent lattice deformation and expansion is also required to describe the excited state spectrum. The kinetics of these structural components match the kinetics of phonons excited from the electron-phonon and phonon-phonon scattering processes following photoexcitation. Separating the contributions of electronic and structural effects on the transient XUV spectra allows the carrier population, the population of phonons involved in inter- and intra-valley electron-phonon scattering, and the population of phonons involved in phonon-phonon scattering to be quantified as a function of delay time.
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Affiliation(s)
| | - Michael Zürch
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Peter M Kraus
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | | | - Angela Lee
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Hung-Tzu Chang
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Christopher J Kaplan
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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Porter IJ, Cushing SK, Carneiro LM, Lee A, Ondry JC, Dahl JC, Chang HT, Alivisatos AP, Leone SR. Photoexcited Small Polaron Formation in Goethite (α-FeOOH) Nanorods Probed by Transient Extreme Ultraviolet Spectroscopy. J Phys Chem Lett 2018; 9:4120-4124. [PMID: 29985006 DOI: 10.1021/acs.jpclett.8b01525] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Small polaron formation limits the mobility and lifetimes of photoexcited carriers in metal oxides. As the ligand field strength increases, the carrier mobility decreases, but the effect on the photoexcited small polaron formation is still unknown. Extreme ultraviolet transient absorption spectroscopy is employed to measure small polaron formation rates and probabilities in goethite (α-FeOOH) crystalline nanorods at pump photon energies from 2.2 to 3.1 eV. The measured polaron formation time increases with excitation photon energy from 70 ± 10 fs at 2.2 eV to 350 ± 30 fs at 2.6 eV, whereas the polaron formation probability (85 ± 10%) remains constant. By comparison to hematite (α-Fe2O3), an oxide analogue, the role of ligand composition and metal center density in small polaron formation time is discussed. This work suggests that incorporating small changes in ligands and crystal structure could enable the control of photoexcited small polaron formation in metal oxides.
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Affiliation(s)
- Ilana J Porter
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Scott K Cushing
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Lucas M Carneiro
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Angela Lee
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - Justin C Ondry
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Jakob C Dahl
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Hung-Tzu Chang
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
| | - A Paul Alivisatos
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Materials Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Materials Science and Engineering , University of California , Berkeley , California 94720 , United States
- Kavli Energy NanoScience Institute , Berkeley , California 94720 , United States
| | - Stephen R Leone
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
- Department of Physics , University of California , Berkeley , California 94720 , United States
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12
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Kraus PM, Zürch M, Cushing SK, Neumark DM, Leone SR. Author Correction: The ultrafast X-ray spectroscopic revolution in chemical dynamics. Nat Rev Chem 2018. [DOI: 10.1038/s41570-018-0016-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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14
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Carneiro LM, Cushing SK, Liu C, Su Y, Yang P, Alivisatos AP, Leone SR. Excitation-wavelength-dependent small polaron trapping of photoexcited carriers in α-Fe 2O 3. Nat Mater 2017; 16:819-825. [PMID: 28692042 DOI: 10.1038/nmat4936] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/26/2017] [Indexed: 05/16/2023]
Abstract
Small polaron formation is known to limit ground-state mobilities in metal oxide photocatalysts. However, the role of small polaron formation in the photoexcited state and how this affects the photoconversion efficiency has yet to be determined. Here, transient femtosecond extreme-ultraviolet measurements suggest that small polaron localization is responsible for the ultrafast trapping of photoexcited carriers in haematite (α-Fe2O3). Small polaron formation is evidenced by a sub-100 fs splitting of the Fe 3p core orbitals in the Fe M2,3 edge. The small polaron formation kinetics reproduces the triple-exponential relaxation frequently attributed to trap states. However, the measured spectral signature resembles only the spectral predictions of a small polaron and not the pre-edge features expected for mid-gap trap states. The small polaron formation probability, hopping radius and lifetime varies with excitation wavelength, decreasing with increasing energy in the t2g conduction band. The excitation-wavelength-dependent localization of carriers by small polaron formation is potentially a limiting factor in haematite's photoconversion efficiency.
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Affiliation(s)
- Lucas M Carneiro
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Scott K Cushing
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Chong Liu
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Yude Su
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Peidong Yang
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Kavli Energy NanoScience Institute, Berkeley, California 94720, USA
| | - A Paul Alivisatos
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Kavli Energy NanoScience Institute, Berkeley, California 94720, USA
| | - Stephen R Leone
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Department of Physics, University of California, Berkeley, California 94720, USA
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Zürch M, Chang HT, Kraus PM, Cushing SK, Borja LJ, Gandman A, Kaplan CJ, Oh MH, Prell JS, Prendergast D, Pemmaraju CD, Neumark DM, Leone SR. Ultrafast carrier thermalization and trapping in silicon-germanium alloy probed by extreme ultraviolet transient absorption spectroscopy. Struct Dyn 2017; 4:044029. [PMID: 28653020 PMCID: PMC5461173 DOI: 10.1063/1.4985056] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Accepted: 05/24/2017] [Indexed: 05/23/2023]
Abstract
Semiconductor alloys containing silicon and germanium are of growing importance for compact and highly efficient photonic devices due to their favorable properties for direct integration into silicon platforms and wide tunability of optical parameters. Here, we report the simultaneous direct and energy-resolved probing of ultrafast electron and hole dynamics in a silicon-germanium alloy with the stoichiometry Si0.25Ge0.75 by extreme ultraviolet transient absorption spectroscopy. Probing the photoinduced dynamics of charge carriers at the germanium M4,5-edge (∼30 eV) allows the germanium atoms to be used as reporter atoms for carrier dynamics in the alloy. The photoexcitation of electrons across the direct and indirect band gap into conduction band (CB) valleys and their subsequent hot carrier relaxation are observed and compared to pure germanium, where the Ge direct [Formula: see text] and Si0.25Ge0.75 indirect gaps ([Formula: see text]) are comparable in energy. In the alloy, comparable carrier lifetimes are observed for the X, L, and Γ valleys in the conduction band. A midgap feature associated with electrons accumulating in trap states near the CB edge following intraband thermalization is observed in the Si0.25Ge0.75 alloy. The successful implementation of the reporter atom concept for capturing the dynamics of the electronic bands by site-specific probing in solids opens a route to study carrier dynamics in more complex materials with femtosecond and sub-femtosecond temporal resolution.
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Affiliation(s)
- Michael Zürch
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Hung-Tzu Chang
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Peter M Kraus
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Scott K Cushing
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Lauren J Borja
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Andrey Gandman
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Christopher J Kaplan
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | | | - James S Prell
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - David Prendergast
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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16
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Zürch M, Chang HT, Borja LJ, Kraus PM, Cushing SK, Gandman A, Kaplan CJ, Oh MH, Prell JS, Prendergast D, Pemmaraju CD, Neumark DM, Leone SR. Direct and simultaneous observation of ultrafast electron and hole dynamics in germanium. Nat Commun 2017; 8:15734. [PMID: 28569752 PMCID: PMC5461502 DOI: 10.1038/ncomms15734] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 04/21/2017] [Indexed: 11/22/2022] Open
Abstract
Understanding excited carrier dynamics in semiconductors is crucial for the development of photovoltaics and efficient photonic devices. However, overlapping spectral features in optical pump-probe spectroscopy often render assignments of separate electron and hole carrier dynamics ambiguous. Here, ultrafast electron and hole dynamics in germanium nanocrystalline thin films are directly and simultaneously observed by ultrafast transient absorption spectroscopy in the extreme ultraviolet at the germanium M4,5 edge. We decompose the spectra into contributions of electronic state blocking and photo-induced band shifts at a carrier density of 8 × 1020 cm−3. Separate electron and hole relaxation times are observed as a function of hot carrier energies. A first-order electron and hole decay of ∼1 ps suggests a Shockley–Read–Hall recombination mechanism. The simultaneous observation of electrons and holes with extreme ultraviolet transient absorption spectroscopy paves the way for investigating few- to sub-femtosecond dynamics of both holes and electrons in complex semiconductor materials and across junctions. Understanding excited carrier dynamics in semiconductors is central to the continued development of optoelectronic devices. Using extreme ultraviolet transient absorption spectroscopy, Zürch et al. directly and simultaneously observe ultrafast electron and hole dynamics in germanium thin films.
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Affiliation(s)
- Michael Zürch
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Hung-Tzu Chang
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Lauren J Borja
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Peter M Kraus
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Scott K Cushing
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Andrey Gandman
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Christopher J Kaplan
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - Myoung Hwan Oh
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - James S Prell
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA
| | - David Prendergast
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Chaitanya D Pemmaraju
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.,Theory Institute for Materials and Energy Spectroscopies, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
| | - Daniel M Neumark
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Stephen R Leone
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720, USA.,Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.,Department of Physics, University of California, Berkeley, California 94720, USA
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17
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Cushing SK, Ding W, Chen G, Wang C, Yang F, Huang F, Wu N. Excitation wavelength dependent fluorescence of graphene oxide controlled by strain. Nanoscale 2017; 9:2240-2245. [PMID: 28124702 DOI: 10.1039/c6nr08286f] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Unlike conventional fluorophores, the fluorescence emission of graphene oxide (GO) sheets can shift hundreds of nanometers as the excitation wavelength increases. The excitation wavelength dependent fluorescence is referred to as a giant red-edge effect and originates in a local reorganization potential slowing down the solvation dynamics of the excited state to the same time scale as the fluorescence lifetime. The present work has discovered that out-of-plane strain in the graphene oxide sheet leads to the intra-layer interaction necessary to slow down the solvation time scale. The oxygen percentage, dopant percentage, disorder, and strain are correlated with the presence and extent of the red-edge effect in oxygen, boron, nitrogen, and fluorine doped graphene oxide. Of these commonly cited possibilities, only out-of-plane strain is directly correlated to the red-edge effect. Furthermore, it is shown that the extent of the red-edge effect, or how far the emission wavelength can shift with increasing excitation wavelength, can be tuned by the electronegativity of the dopant. The present work interprets why the giant red-edge effect is present in some GO sheets but not in other GO sheets.
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Affiliation(s)
- Scott K Cushing
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA. and Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506-6315, USA
| | - Weiqiang Ding
- Department of Industrial and Management Systems Engineering, West Virginia University, Morgantown, WV 26506-6070, USA
| | - Gang Chen
- Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA
| | - Chao Wang
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China.
| | - Feng Yang
- Department of Industrial and Management Systems Engineering, West Virginia University, Morgantown, WV 26506-6070, USA
| | - Fuqiang Huang
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, P. R. China.
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA.
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18
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Zheng P, Cushing SK, Suri S, Wu N. Tailoring plasmonic properties of gold nanohole arrays for surface-enhanced Raman scattering. Phys Chem Chem Phys 2016; 17:21211-9. [PMID: 25586930 DOI: 10.1039/c4cp05291a] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The wide plasmonic tuning range of nanotriangle and nanohole array patterns fabricated by nanosphere lithography makes them promising in surface-enhanced Raman scattering (SERS) sensors. Unfortunately, it is challenging to optimize these patterns for SERS sensing because their optical response is a complex mixture of localized surface plasmon resonance (SPR) and propagating surface plasmon polariton (SPP). In this paper, transmission and reflection measurements are combined with finite difference time domain simulations to identify and separate each plasmonic mode, discerning which resonance leads to the electromagnetic field enhancement. The SERS enhancement is found to be dominated by the absorption, which is shifted from the transmission and reflection dips usually used as tuning points, and by the 'gap' defects formed within the pattern. These effects have different spectral and geometric dependences, forming two optimization curves which can be used to predict the best performance for a given excitation wavelength. The developed model is verified with experimental SERS measurements for several nanohole sizes and periodicities, and then used to give optimal fabrication parameters for a range of measurement conditions. The results will promote the application of two-dimensional plasmonic nanoarrays in SERS sensors.
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Affiliation(s)
- Peng Zheng
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA.
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19
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Abstract
Plasmonics allows extraordinary control of light, making it attractive for application in solar energy harvesting. In metal-semiconductor heterojunctions, plasmons can enhance photoconversion in the semiconductor via three mechanisms, including light trapping, hot electron/hole transfer, and plasmon-induced resonance energy transfer (PIRET). To understand the plasmonic enhancement, the metal's geometry, constituent metal, and interface must be viewed in terms of the effects on the plasmon's dephasing and decay route. To simplify design of plasmonic metal-semiconductor heterojunctions for high-efficiency solar energy conversion, the parameters controlling the plasmonic enhancement can be distilled to the dephasing time. The plasmonic geometry can then be further refined to optimize hot carrier transfer, PIRET, or light trapping.
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Affiliation(s)
- Scott K Cushing
- Department of Physics and Astronomy, West Virginia University , Morgantown, West Virginia 26506-6315, United States
- Department of Mechanical and Aerospace Engineering, West Virginia University , Morgantown, West Virginia 26506-6106, United States
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering, West Virginia University , Morgantown, West Virginia 26506-6106, United States
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20
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Zheng P, Li M, Jurevic R, Cushing SK, Liu Y, Wu N. A gold nanohole array based surface-enhanced Raman scattering biosensor for detection of silver(I) and mercury(II) in human saliva. Nanoscale 2015; 7:11005-12. [PMID: 26008641 PMCID: PMC4476066 DOI: 10.1039/c5nr02142a] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
A surface-enhanced Raman scattering (SERS) biosensor has been developed by incorporating a gold nanohole array with a SERS probe (a gold nanostar@Raman-reporter@silica sandwich structure) into a single detection platform via DNA hybridization, which circumvents the nanoparticle aggregation and the inefficient Raman scattering issues. Strong plasmonic coupling between the Au nanostar and the Au nanohole array results in a large enhancement of the electromagnetic field, leading to amplification of the SERS signal. The SERS sensor has been used to detect Ag(I) and Hg(II) ions in human saliva because both the metal ions could be released from dental amalgam fillings. The developed SERS sensor can be adapted as a general detection platform for non-invasive measurements of a wide range of analytes such as metal ions, small molecules, DNA and proteins in body fluids.
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Affiliation(s)
- Peng Zheng
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA.
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21
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Meng F, Cushing SK, Li J, Hao S, Wu N. Enhancement of Solar Hydrogen Generation by Synergistic Interaction of La2Ti2O7 Photocatalyst with Plasmonic Gold Nanoparticles and Reduced Graphene Oxide Nanosheets. ACS Catal 2015. [DOI: 10.1021/cs5016194] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Fanke Meng
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Scott K. Cushing
- Department
of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Jiangtian Li
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Shimeng Hao
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Nianqiang Wu
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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22
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Abstract
Surface plasmon resonance (SPR) has found extensive applications in chemi-sensors and biosensors. Plasmons play different roles in different types of optical sensors. SPR transduces a signal in a colorimetric sensor through shifts in the spectral position and intensity in response to external stimuli. SPR can also concentrate the incident electromagnetic field in a nanostructure, modulating fluorescence emission and enabling plasmon-enhanced fluorescence to be used for ultrasensitive detection. Furthermore, plasmons have been extensively used for amplifying a Raman signal in a surface-enhanced Raman scattering sensor. This paper presents a review of recent research progress in plasmon-enhanced optical sensing, giving emphasis on the physical basis of plasmon-enhanced sensors and how these principles guide the design of sensors. In particular, this paper discusses the design strategies for nanomaterials and nanostructures to plasmonically enhance optical sensing signals, also highlighting the applications of plasmon-enhanced optical sensors in healthcare, homeland security, food safety and environmental monitoring.
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Affiliation(s)
- Ming Li
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA.
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23
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Cushing SK, Bristow AD, Wu N. Theoretical maximum efficiency of solar energy conversion in plasmonic metal–semiconductor heterojunctions. Phys Chem Chem Phys 2015; 17:30013-22. [PMID: 26497739 DOI: 10.1039/c5cp04512f] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The plasmon's dephasing is used to calculate optimal design guidelines and the maximum efficiency for plasmon enhanced solar energy conversion.
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Affiliation(s)
- Scott K. Cushing
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
- Department of Mechanical and Aerospace Engineering
| | - Alan D. Bristow
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
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24
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Yost BT, Cushing SK, Meng F, Bright J, Bas DA, Wu N, Bristow AD. Investigation of band gap narrowing in nitrogen-doped La2Ti2O7 with transient absorption spectroscopy. Phys Chem Chem Phys 2015; 17:31039-43. [PMID: 26531849 DOI: 10.1039/c5cp05637c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Doping a continuum of states is shown to preserve excited carrier lifetimes and mobility, increasing photocatalysis across the UV-visible spectrum.
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Affiliation(s)
- Brandon T. Yost
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
| | - Scott K. Cushing
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
- Department of Mechanical and Aerospace Engineering
| | - Fanke Meng
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
| | - Joeseph Bright
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
| | - Derek A. Bas
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
| | - Alan D. Bristow
- Department of Physics and Astronomy
- West Virginia University
- Morgantown
- USA
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25
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Zhang J, Dang W, Ao Z, Cushing SK, Wu N. Band gap narrowing in nitrogen-doped La2Ti2O7 predicted by density-functional theory calculations. Phys Chem Chem Phys 2015; 17:8994-9000. [PMID: 25751702 DOI: 10.1039/c5cp00157a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
NS co-existing with VO in La2Ti2O7 narrows the band gap and removes the localized energy state, leading to a strong visible light photocatalytic activity and enhancement of the UV performance.
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Affiliation(s)
- Junying Zhang
- Department of Physics
- Beihang University
- Beijing 100191
- China
| | - Wenqiang Dang
- Department of Physics
- Beihang University
- Beijing 100191
- China
| | - Zhimin Ao
- Center for Clean Energy Technology
- School of Chemistry and Forensic Science
- University of Technology Sydney
- P.O. Box 123, Broadway
- Sydney
| | - Scott K. Cushing
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering
- West Virginia University
- Morgantown
- USA
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26
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Li J, Cushing SK, Zheng P, Senty T, Meng F, Bristow AD, Manivannan A, Wu N. Solar Hydrogen Generation by a CdS-Au-TiO2 Sandwich Nanorod Array Enhanced with Au Nanoparticle as Electron Relay and Plasmonic Photosensitizer. J Am Chem Soc 2014; 136:8438-49. [PMID: 24836347 DOI: 10.1021/ja503508g] [Citation(s) in RCA: 236] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Jiangtian Li
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Scott K. Cushing
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
- Department
of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Peng Zheng
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Tess Senty
- Department
of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Fanke Meng
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Alan D. Bristow
- Department
of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Ayyakkannu Manivannan
- National
Energy Technology Laboratory, U.S. Department of Energy, Morgantown, West Virginia 26507, United States
| | - Nianqiang Wu
- Department
of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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27
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Abstract
The peak fluorescence emission of conventional fluorophores such as organic dyes and inorganic quantum dots is independent of the excitation wavelength. In contrast, the position of the peak fluorescence of graphene oxide (GO) in a polar solvent is heavily dependent on the excitation wavelength. The present work has discovered that the strong excitation wavelength dependent fluorescence in GO is originated from the "giant red-edge effect", which breaks Kasha's rule. When GO sheets are present in a polar solvent, the solvation dynamics slow down to the same time scale as the fluorescence due to the local environment of the GO sheet. Consequently, the fluorescence peak of GO broadens and red-shifts up to 200 nm with an increase in the excitation wavelength. The giant red-edge effect of GO disappears in a nonpolar solvent, leading to a narrow fluorescence peak that is independent of the excitation wavelength. Discovery of the underlying strong excitation wavelength dependent fluorescence mechanism provides guidelines for the design of graphene oxide-based optical devices.
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Affiliation(s)
- Scott K Cushing
- Department of Mechanical and Aerospace Engineering, West Virginia University , Morgantown, West Virginia 26506-6106, United States
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28
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Li M, Zhang J, Dang W, Cushing SK, Guo D, Wu N, Yin P. Photocatalytic hydrogen generation enhanced by band gap narrowing and improved charge carrier mobility in AgTaO3 by compensated co-doping. Phys Chem Chem Phys 2013; 15:16220-6. [PMID: 23995011 DOI: 10.1039/c3cp51902c] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The correlation of the electronic band structure with the photocatalytic activity of AgTaO3 has been studied by simulation and experiments. Doping wide band gap oxide semiconductors usually introduces discrete mid-gap states, which extends the light absorption but has limited benefit for photocatalytic activity. Density functional theory (DFT) calculations show that compensated co-doping in AgTaO3 can overcome this problem by increasing the light absorption and simultaneously improving the charge carrier mobility. N/H and N/F co-doping can delocalize the discrete mid-gap states created by sole N doping in AgTaO3, which increases the band curvature and the electron-to-hole effective mass ratio. In particular, N/F co-doping creates a continuum of states that extend the valence band of AgTaO3. N/F co-doping thus improves the light absorption without creating the mid-gap states, maintaining the necessary redox potentials for water splitting and preventing from charge carrier trapping. The experimental results have confirmed that the N/F-codoped AgTaO3 exhibits a red-shift of the absorption edge in comparison with the undoped AgTaO3, leading to remarkable enhancement of photocatalytic activity toward hydrogen generation from water.
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Affiliation(s)
- Min Li
- Key Laboratory of Micro-nano Measurement, Manipulation and Physics (Ministry of Education), Department of Physics, Beihang University, Beijing 100191, P. R. China.
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29
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Meng F, Li J, Cushing SK, Zhi M, Wu N. Solar hydrogen generation by nanoscale p-n junction of p-type molybdenum disulfide/n-type nitrogen-doped reduced graphene oxide. J Am Chem Soc 2013; 135:10286-9. [PMID: 23808935 DOI: 10.1021/ja404851s] [Citation(s) in RCA: 287] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Molybdenum disulfide (MoS2) is a promising candidate for solar hydrogen generation but it alone has negligible photocatalytic activity. In this work, 5-20 nm sized p-type MoS2 nanoplatelets are deposited on the n-type nitrogen-doped reduced graphene oxide (n-rGO) nanosheets to form multiple nanoscale p-n junctions in each rGO nanosheet. The p-MoS2/n-rGO heterostructure shows significant photocatalytic activity toward the hydrogen evolution reaction (HER) in the wavelength range from the ultraviolet light through the near-infrared light. The photoelectrochemical measurement shows that the p-MoS2/n-rGO junction greatly enhances the charge generation and suppresses the charge recombination, which is responsible for enhancement of solar hydrogen generation. The p-MoS2/n-rGO is an earth-abundant and environmentally benign photocatalyst for solar hydrogen generation.
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Affiliation(s)
- Fanke Meng
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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30
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Li M, Cushing SK, Zhang J, Suri S, Evans R, Petros WP, Gibson LF, Ma D, Liu Y, Wu N. Three-dimensional hierarchical plasmonic nano-architecture enhanced surface-enhanced Raman scattering immunosensor for cancer biomarker detection in blood plasma. ACS Nano 2013; 7:4967-76. [PMID: 23659430 PMCID: PMC3732798 DOI: 10.1021/nn4018284] [Citation(s) in RCA: 165] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A three-dimensional (3D) hierarchical plasmonic nano-architecture has been designed for a sensitive surface-enhanced Raman scattering (SERS) immunosensor for protein biomarker detection. The capture antibody molecules are immobilized on a plasmonic gold triangle nanoarray pattern. On the other hand, the detection antibody molecules are linked to the gold nanostar@Raman reporter@silica sandwich nanoparticles. When protein biomarkers are present, the sandwich nanoparticles are captured over the gold triangle nanoarray, forming a confined 3D plasmonic field, leading to the enhanced electromagnetic field in intensity and in 3D space. As a result, the Raman reporter molecules are exposed to a high density of "hot spots", which amplifies the Raman signal remarkably, improving the sensitivity of the SERS immunosensor. This SERS immunosensor exhibits a wide linear range (0.1 pg/mL to 10 ng/mL) and a low limit of detection (7 fg/mL) toward human immunoglobulin G protein in the buffer solution. This biosensor has been successfully used for detection of the vascular endothelial growth factor in the human blood plasma from clinical breast cancer patient samples.
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Affiliation(s)
- Ming Li
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
| | - Scott K. Cushing
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
- Department of Physics, West Virginia University, Morgantown, WV 26506, USA
| | - Jianming Zhang
- Institut National de la Recherche Scientifique, INRS-Énergie, Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
| | - Savan Suri
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
| | - Rebecca Evans
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV 26506, USA
- Alexander B. Osborn Hematopoietic Malignancy and Transplantation Program of the Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV 26506, USA
| | - William P. Petros
- Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506, USA
- Alexander B. Osborn Hematopoietic Malignancy and Transplantation Program of the Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV 26506, USA
| | - Laura F. Gibson
- Department of Microbiology, Immunology, and Cell Biology, West Virginia University, Morgantown, WV 26506, USA
- Alexander B. Osborn Hematopoietic Malignancy and Transplantation Program of the Mary Babb Randolph Cancer Center, West Virginia University, Morgantown, WV 26506, USA
| | - Dongling Ma
- Institut National de la Recherche Scientifique, INRS-Énergie, Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Québec J3X 1S2, Canada
| | - Yuxin Liu
- Lane Department of Computer Science and Electrical Engineering, West Virginia University, Morgantown, WV 26506, USA
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV 26506-6106, USA
- Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506, USA
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Liang H, Rossouw D, Zhao H, Cushing SK, Shi H, Korinek A, Xu H, Rosei F, Wang W, Wu N, Botton GA, Ma D. Asymmetric Silver “Nanocarrot” Structures: Solution Synthesis and Their Asymmetric Plasmonic Resonances. J Am Chem Soc 2013; 135:9616-9. [PMID: 23758332 DOI: 10.1021/ja404345s] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Hongyan Liang
- INRS-EMT, Université du Québec, 1650 Boul. Lionel-Boulet, Varennes,
QC, Canada J3X 1S2
| | - David Rossouw
- Department
of Materials Science
and Engineering, McMaster University, 1280
Main Street West, Hamilton, ON, Canada L8S 4L7
| | - Haiguang Zhao
- INRS-EMT, Université du Québec, 1650 Boul. Lionel-Boulet, Varennes,
QC, Canada J3X 1S2
| | - Scott K. Cushing
- Department of Mechanical & Aerospace Engineerings, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Honglong Shi
- School of Science, Minzu University of China, Beijing 100081, P. R. China
| | - Andreas Korinek
- Department
of Materials Science
and Engineering, McMaster University, 1280
Main Street West, Hamilton, ON, Canada L8S 4L7
| | - Hongxing Xu
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R.
China
| | - Federico Rosei
- INRS-EMT, Université du Québec, 1650 Boul. Lionel-Boulet, Varennes,
QC, Canada J3X 1S2
| | - Wenzhong Wang
- School of Science, Minzu University of China, Beijing 100081, P. R. China
| | - Nianqiang Wu
- Department of Mechanical & Aerospace Engineerings, West Virginia University, Morgantown, West Virginia 26506, United States
| | - Gianluigi A. Botton
- Department
of Materials Science
and Engineering, McMaster University, 1280
Main Street West, Hamilton, ON, Canada L8S 4L7
| | - Dongling Ma
- INRS-EMT, Université du Québec, 1650 Boul. Lionel-Boulet, Varennes,
QC, Canada J3X 1S2
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Meng F, Li J, Cushing SK, Bright J, Zhi M, Rowley JD, Hong Z, Manivannan A, Bristow AD, Wu N. Photocatalytic Water Oxidation by Hematite/Reduced Graphene Oxide Composites. ACS Catal 2013. [DOI: 10.1021/cs300740e] [Citation(s) in RCA: 214] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
| | | | | | | | | | | | - Zhanglian Hong
- State Key Laboratory of Silicon Materials, Department of Materials Science & Engineering, Zhejiang University, Hangzhou 310027, P.R. China
| | - Ayyakkannu Manivannan
- National Energy Technology Laboratory, U.S. Department of Energy, Morgantown, West Virginia
26507, United States
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Li M, Cushing SK, Liang H, Suri S, Ma D, Wu N. Plasmonic nanorice antenna on triangle nanoarray for surface-enhanced Raman scattering detection of hepatitis B virus DNA. Anal Chem 2013; 85:2072-8. [PMID: 23320458 DOI: 10.1021/ac303387a] [Citation(s) in RCA: 122] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The sensitivity and the limit of detection of Raman sensors are limited by the extremely small scattering cross section of Raman labels. Silver nanorice antennae are coupled with a patterned gold triangle nanoarray chip to create spatially broadened plasmonic "hot spots", which enables a large density of Raman labels to experience strong local electromagnetic field. Finite difference time domain simulations have confirmed that the quasi-periodic structure increases the intensity and the area of the surface plasmon resonance (SPR), which enhances the surface-enhanced Raman scattering (SERS) signal significantly. The SERS signal of the nanorice/DNA/nanoarray chip is compared with that of the nanorice/DNA/film chip. The SERS signal is greatly enhanced when the Ag nanorices are coupled to the periodic Au nanoarray instead of the planar film chip. The resulting spatially broadened SPR field enables the SERS biosensor with a limit of detection of 50 aM toward hepatitis B virus DNA with the capability of discriminating a single-base mutant of DNA. This sensing platform can be extended to detect other chemical species and biomolecules such as proteins and small molecules.
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Affiliation(s)
- Ming Li
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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Li J, Cushing SK, Bright J, Meng F, Senty TR, Zheng P, Bristow AD, Wu N. Ag@Cu2O Core-Shell Nanoparticles as Visible-Light Plasmonic Photocatalysts. ACS Catal 2012. [DOI: 10.1021/cs300672f] [Citation(s) in RCA: 427] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Jiangtian Li
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Scott K. Cushing
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Joeseph Bright
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Fanke Meng
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Tess R. Senty
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Peng Zheng
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Alan D. Bristow
- Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315, United States
| | - Nianqiang Wu
- Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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Cushing SK, Li J, Meng F, Senty TR, Suri S, Zhi M, Li M, Bristow AD, Wu N. Photocatalytic Activity Enhanced by Plasmonic Resonant Energy Transfer from Metal to Semiconductor. J Am Chem Soc 2012; 134:15033-41. [PMID: 22891916 DOI: 10.1021/ja305603t] [Citation(s) in RCA: 541] [Impact Index Per Article: 45.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Scott K. Cushing
- Department of Physics, West Virginia University, Morgantown, West Virginia
26506-6315, United States
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Jiangtian Li
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Fanke Meng
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Tess R. Senty
- Department of Physics, West Virginia University, Morgantown, West Virginia
26506-6315, United States
| | - Savan Suri
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Mingjia Zhi
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Ming Li
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
| | - Alan D. Bristow
- Department of Physics, West Virginia University, Morgantown, West Virginia
26506-6315, United States
| | - Nianqiang Wu
- Department of Mechanical and
Aerospace Engineering, West Virginia University, Morgantown, West Virginia 26506-6106, United States
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Li M, Cushing SK, Zhang J, Lankford J, Aguilar ZP, Ma D, Wu N. Shape-dependent surface-enhanced Raman scattering in gold-Raman probe-silica sandwiched nanoparticles for biocompatible applications. Nanotechnology 2012; 23:115501. [PMID: 22383452 DOI: 10.1088/0957-4484/23/11/115501] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
To meet the requirement of Raman probes (labels) for biocompatible applications, a synthetic approach has been developed to sandwich the Raman-probe (malachite green isothiocyanate, MGITC) molecules between the gold core and the silica shell in gold-SiO₂ composite nanoparticles. The gold-MGITC-SiO₂ sandwiched structure not only prevents the Raman probe from leaking out but also improves the solubility of the nanoparticles in organic solvents and in aqueous solutions even with high ionic strength. To amplify the Raman signal, three types of core, gold nanospheres, nanorods and nanostars, have been chosen as the substrates of the Raman probe. The effect of the core shape on the surface-enhanced Raman scattering (SERS) has been investigated. The colloidal nanostars showed the highest SERS enhancement factor while the nanospheres possessed the lowest SERS activity under excitation with 532 and 785 nm lasers. Three-dimensional finite-difference time domain (FDTD) simulation showed significant differences in the local electromagnetic field distributions surrounding the nanospheres, nanorods, and nanostars, which were induced by the localized surface plasmon resonance (LSPR). The electromagnetic field was enhanced remarkably around the two ends of the nanorods and around the sharp tips of the nanostars. This local electromagnetic enhancement made the dominant contribution to the SERS enhancement. Both the experiments and the simulation revealed the order nanostars > nanorods > nanospheres in terms of the enhancement factor. Finally, the biological application of the nanostar-MGITC-SiO₂ nanoparticles has been demonstrated in the monitoring of DNA hybridization. In short, the gold–MGITC-SiO₂ sandwiched nanoparticles can be used as a Raman probe that features high sensitivity, good water solubility and stability, low-background fluorescence, and the absence of photobleaching for future biological applications.
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Affiliation(s)
- Ming Li
- Department of Mechanical and Aerospace Engineering, WVNano Initiative, West Virginia University, Morgantown, WV 26506, USA
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