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Hardy M, Goldberg Oppenheimer P. 'When is a hotspot a good nanospot' - review of analytical and hotspot-dominated surface enhanced Raman spectroscopy nanoplatforms. NANOSCALE 2024; 16:3293-3323. [PMID: 38273798 PMCID: PMC10868661 DOI: 10.1039/d3nr05332f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2023] [Accepted: 01/13/2024] [Indexed: 01/27/2024]
Abstract
Substrate development in surface-enhanced Raman spectroscopy (SERS) continues to attract research interest. In order to determine performance metrics, researchers in foundational SERS studies use a variety of experimental means to characterize the nature of substrates. However, often this process would appear to be performed indiscriminately without consideration for the physical scale of the enhancement phenomena. Herein, we differentiate between SERS substrates whose primary enhancing structures are on the hundreds of nanometer scale (analytical SERS nanosubstrates) and those whose main mechanism derives from nanometric-sized gaps (hot-spot dominated SERS substrates), assessing the utility of various characterization methods for each substrate class. In this context, characterization approaches in white-light spectroscopy, electron beam methods, and scanning probe spectroscopies are reviewed. Tip-enhanced Raman spectroscopy, wavelength-scanned SERS studies, and the impact of surface hydrophobicity are also discussed. Conclusions are thus drawn on the applicability of each characterization technique regarding amenability for SERS experiments that have features at different length scales. For instance, while white light spectroscopy can provide an indication of the plasmon resonances associated with 10 s-100 s nm-scale structures, it may not reveal information about finer surface texturing on the true nm-scale, critical for SERS' sensitivity, and in need of investigation via scanning probe techniques.
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Affiliation(s)
- Mike Hardy
- School of Chemical Engineering, College of Engineering and Physical Sciences, University of Birmingham, B15 2TT, UK.
- Centre for Quantum Materials and Technologies, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN, UK.
| | - Pola Goldberg Oppenheimer
- School of Chemical Engineering, College of Engineering and Physical Sciences, University of Birmingham, B15 2TT, UK.
- Healthcare Technologies Institute, Institute of Translational Medicine, Birmingham B15 2TH, UK
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2
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Broccoli A, Vollertsen AR, Roels P, van Vugt A, van den Berg A, Odijk M. Nanoparticle Printing for Microfluidic Applications: Bipolar Electrochemistry and Localized Raman Sensing Spots. MICROMACHINES 2023; 14:453. [PMID: 36838154 PMCID: PMC9967861 DOI: 10.3390/mi14020453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
The local integration of metal nanoparticle films on 3D-structured polydimethylsiloxane (PDMS)-based microfluidic devices is of high importance for applications including electronics, electrochemistry, electrocatalysis, and localized Raman sensing. Conventional processes to locally deposit and pattern metal nanoparticles require multiple steps and shadow masks, or access to cleanroom facilities, and therefore, are relatively imprecise, or time and cost-ineffective. As an alternative, we present an aerosol-based direct-write method, in which patterns of nanoparticles generated via spark ablation are locally printed with sub-mm size and precision inside of microfluidic structures without the use of lithography or other masking methods. As proof of principle, films of Pt or Ag nanoparticles were printed in the chambers of a multiplexed microfluidic device and successfully used for two different applications: Screening electrochemical activity in a high-throughput fashion, and localized sensing of chemicals via surface-enhanced Raman spectroscopy (SERS). The versatility of the approach will enable the generation of functional microfluidic devices for applications that include sensing, high-throughput screening platforms, and microreactors using catalytically driven chemical conversions.
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Affiliation(s)
- Alessia Broccoli
- BIOS Lab on a Chip Group, MESA+ Institute for Nanotechnology, Max Planck Center for Complex Fluid Dynamics, University of Twente, 7500 AE Enschede, The Netherlands
| | - Anke R. Vollertsen
- Department of Applied Stem Cell Technologies, TechMed Centre, University of Twente, 7500 AE Enschede, The Netherlands
| | | | | | - Albert van den Berg
- BIOS Lab on a Chip Group, MESA+ Institute for Nanotechnology, Max Planck Center for Complex Fluid Dynamics, University of Twente, 7500 AE Enschede, The Netherlands
| | - Mathieu Odijk
- BIOS Lab on a Chip Group, MESA+ Institute for Nanotechnology, Max Planck Center for Complex Fluid Dynamics, University of Twente, 7500 AE Enschede, The Netherlands
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3
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Wang K, Qiu Z, Qin Y, Feng L, Huang L, Xiao G. Preparation and SERS performance of silver nanowires arrays on paper by automatic writing method. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2022; 281:121580. [PMID: 35809423 DOI: 10.1016/j.saa.2022.121580] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 06/15/2022] [Accepted: 06/29/2022] [Indexed: 06/15/2023]
Abstract
Silver nanowire ink was written on the surface of drawing paper by automatic writing method. Scanning electron microscopy was used to characterize the surface morphologies of the drawing paper before and after writing silver nanowires. The effects of fabrication parameters and measurement parameters on silver nanowires arrays were investigated. Crystal violet was selected as the probe molecule to study the SERS performance of silver nanowires arrays. The detection limit of crystal violet was as low as 10-15 mol/L. The uniformity and repeatability of the arrays were also explored, and the relative standard deviation values were about 10%. Moreover, silver nanowires arrays were also relatively stable that SERS signals were still observed after ten weeks. Detection of the crystal violet residue was further achieved on the substrates by continuously pressing nine times. In addition, silver nanowires arrays were also applied to the quantitative analyses of 2, 2'-bipyridyl.
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Affiliation(s)
- Kun Wang
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China
| | - Zhiyu Qiu
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China
| | - Yufei Qin
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China
| | - Longxiu Feng
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China
| | - Lei Huang
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China
| | - Guina Xiao
- Department of Physics, Shanghai Normal University, Guilin Road 100, Shanghai 200234, PR China.
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4
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Rathod J, Byram C, Kanaka RK, Sree Satya Bharati M, Banerjee D, Akkanaboina M, Soma VR. Hybrid Surface-Enhanced Raman Scattering Substrates for the Trace Detection of Ammonium Nitrate, Thiram, and Nile Blue. ACS OMEGA 2022; 7:15969-15981. [PMID: 35571848 PMCID: PMC9096967 DOI: 10.1021/acsomega.2c01095] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Accepted: 04/18/2022] [Indexed: 06/15/2023]
Abstract
We report the fabrication and performance evaluation of hybrid surface-enhanced Raman scattering (SERS) substrates involving laser ablation and chemical routes for the trace-level detection of various analyte molecules. Initially, picosecond laser ablation experiments under ambient conditions were performed on pure silver (Ag) and gold (Au) substrates to achieve distinct nanosized features on the surface. The properties of the generated surface features on laser-processed portions of Ag/Au targets were systematically analyzed using UV-visible reflection and field emission scanning electron microscopy studies. Later, hybrid-SERS substrates were achieved by grafting the chemically synthesized Au nanostars on the plain and laser-processed plasmonic targets. Subsequently, we employed these as SERS platforms for the detection of a pesticide (thiram), a molecule used in explosive compositions [ammonium nitrate (AN)], and a dye molecule [Nile blue (NB)]. A comparative SERS study between the Au nanostar-decorated bare glass, silicon, Ag, Au, and laser-processed Ag and Au targets has been established. Our studies and the obtained data have unambiguously determined that laser-processed Ag structures have demonstrated reasonably good enhancements in the Raman signal intensities for distinct analytes among other substrates. Importantly, the fabricated hybrid SERS substrate of "Au nanostar-decorated laser-processed Ag" exhibited up to eight times enhancement in the SERS intensity compared to laser-processed Ag (without nanostars), as well as up to three times enhancement than the Au nanostar-loaded plain Ag substrates. Additionally, the achieved detection limits from the Au nanostar-decorated laser-processed Ag SERS substrate were ∼50 pM, ∼5 nM, and ∼5 μM for NB, thiram, and AN, respectively. The estimated enhancement factors accomplished from the Au nanostar-decorated laser-processed Ag substrate were ∼106, ∼106, and ∼104 for NB, thiram, and AN, respectively.
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Affiliation(s)
- Jagannath Rathod
- Advanced
Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Chandu Byram
- Advanced
Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Ravi Kumar Kanaka
- School
of Physics, University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Moram Sree Satya Bharati
- Advanced
Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana, India
| | - Dipanjan Banerjee
- Advanced
Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana, India
| | | | - Venugopal Rao Soma
- Advanced
Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046, Telangana, India
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5
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Bonyár A. Maximizing the Surface Sensitivity of LSPR Biosensors through Plasmon Coupling-Interparticle Gap Optimization for Dimers Using Computational Simulations. BIOSENSORS 2021; 11:bios11120527. [PMID: 34940284 PMCID: PMC8699530 DOI: 10.3390/bios11120527] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 12/13/2021] [Accepted: 12/18/2021] [Indexed: 05/03/2023]
Abstract
The bulk and surface refractive index sensitivities of LSPR biosensors, consisting of coupled plasmonic nanosphere and nano-ellipsoid dimers, were investigated by simulations using the boundary element method (BEM). The enhancement factor, defined as the ratio of plasmon extinction peak shift of multi-particle and single-particle arrangements caused by changes in the refractive index of the environment, was used to quantify the effect of coupling on the increased sensitivity of the dimers. The bulk refractive index sensitivity (RIS) was obtained by changing the dielectric medium surrounding the nanoparticles, while the surface sensitivity was modeled by depositing dielectric layers on the nanoparticle in an increasing thickness. The results show that by optimizing the interparticle gaps for a given layer thickness, up to ~80% of the optical response range of the nanoparticles can be utilized by confining the plasmon field between the particles, which translates into an enhancement of ~3-4 times compared to uncoupled, single particles with the same shape and size. The results also show that in these cases, the surface sensitivity enhancement is significantly higher than the bulk RI sensitivity enhancement (e.g., 3.2 times vs. 1.8 times for nanospheres with a 70 nm diameter), and thus the sensors' response for molecular interactions is higher than their RIS would indicate. These results underline the importance of plasmonic coupling in the optimization of nanoparticle arrangements for biosensor applications. The interparticle gap should be tailored with respect to the size of the used receptor/target molecules to maximize the molecular sensitivity, and the presented methodology can effectively aid the optimization of fabrication technologies.
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Affiliation(s)
- Attila Bonyár
- Department of Electronics Technology, Faculty of Electrical Engineering and Informatics, Budapest University of Technology and Economics, H-1111 Budapest, Hungary
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6
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Dong J, Feng H, Wang X, Chen S, Wang S, Zhang C, Liu Q. Transverse and longitudinal coupling of LSPPs in isolated triangular Al-SiO 2-Al hybrid nanoplates for generation of local electromagnetic fields with enhanced intensity and increased decay time. NANOTECHNOLOGY 2021; 32:505708. [PMID: 34530404 DOI: 10.1088/1361-6528/ac2767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/16/2021] [Indexed: 06/13/2023]
Abstract
Achieving a large enhancement of local electromagnetic fields in the ultraviolet waveband is desirable for some applications such as surface-enhanced Raman scattering and surface-enhanced fluorescence. In addition, it is more significant for some applications such as plasmon-enhanced harmonic generation to enhance the intensity of local electromagnetic fields and increase their decay time at the same time. In this paper, using the finite-difference time-domain method, we numerically demonstrate that using the linearly polarized light with a wavelength of 325 nm as the illumination light, an isolated triangular Al-SiO2-Al hybrid nanoplate with optimized geometric parameters can produce a local electric field enhanced by a factor of about 108 at one of its top apexes, and produce two local electric fields enhanced by a factor of about 150 at two transverse dielectric/metal interfaces of one of its longitudinal side edges. Moreover, we also numerically demonstrate that the decay time of enhanced local electric fields produced by the isolated triangular Al-SiO2-Al hybrid nanoplate is about 1.6 times as large as that of enhanced local electric fields produced by an isolated triangular Al nanoplate. These unique properties of the isolated triangular Al-SiO2-Al hybrid nanoplate arise because of both the transverse coupling and the longitudinal coupling of localized surface plasmon polaritons in this structure. Our findings make triangular Al-SiO2-Al hybrid nanoplates very promising for application in many fields such as surface-enhanced Raman scattering and plasmon-enhanced harmonic generation.
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Affiliation(s)
- Jianjie Dong
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
| | - Huimin Feng
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
- School of Astronautics, Beihang University, Beijing 100191, People's Republic of China
| | - Xiaofeng Wang
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
| | - Shengyao Chen
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
| | - Shu Wang
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
| | - Chen Zhang
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
| | - Qian Liu
- Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190, People's Republic of China
- University of Chinese Academy of Science, Beijing 100049, People's Republic of China
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7
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Xiao D, Jie Z, Ma Z, Ying Y, Guo X, Wen Y, Yang H. Fabrication of homogeneous waffle-like silver composite substrate for Raman determination of trace chloramphenicol. Mikrochim Acta 2020; 187:593. [PMID: 33026513 DOI: 10.1007/s00604-020-04567-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 09/25/2020] [Indexed: 11/25/2022]
Abstract
Waffle-like anodized aluminum oxide homogeneously immobilized with Ag nanoparticles (AAO/Ag) is rationally designed and fabricated as surface-enhanced Raman scattering (SERS) substrate. The as-prepared SERS substrate is characterized with transmission electron microscope (TEM), scanning electron microscopy (SEM), UV-Vis spectrophotometer, and Fourier transform infrared spectrometer (FT-IR). The AAO/Ag substrate shows good uniformity of the Raman signals (RSD = 7.02%) due to waffle-like AAO supporting the well-dispersed Ag nanoparticles. For real application, the AAO/Ag substrate is used for rapid determination of chloramphenicol (CAP) in honey with low detection limit (4.0 × 10-9 mol L-1) and good linearity from 1.0 × 10-5 to 1.0 × 10-8 mol L-1 based on the SERS peak at 1348 cm-1. The better accumulation in the short pore path of AAO improves the target molecule approaching into the vicinity of hot spots of Ag nanoparticles. The high selectivity for CAP is attributed to the strong interaction between -NO2 group in CAP and the composite substrate. Schematic representation of the preparation of SERS substrate, AAO150/Ag10-5 composite nanoparticles, and antibiotic determination.
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Affiliation(s)
- Dongfang Xiao
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China
| | - Zhishun Jie
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China
| | - Zhiyuan Ma
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China
| | - Ye Ying
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China.
| | - Xiaoyu Guo
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China
| | - Ying Wen
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China
| | - Haifeng Yang
- Department of Chemistry, Key Laboratory of Resource Chemistry of Ministry of Education, 100 Guilin Road, Shanghai, 200234, People's Republic of China.
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8
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Fabrication, Characterization, and Application of Large-Scale Uniformly Hybrid Nanoparticle-Enhanced Raman Spectroscopy Substrates. MICROMACHINES 2019; 10:mi10050282. [PMID: 31035552 PMCID: PMC6562888 DOI: 10.3390/mi10050282] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 04/18/2019] [Accepted: 04/22/2019] [Indexed: 12/13/2022]
Abstract
Surface-enhanced Raman spectroscopy (SERS) substrates with high sensitivity and reproducibility are highly desirable for high precision and even molecular-level detection applications. Here, large-scale uniformly hybrid nanoparticle-enhanced Raman spectroscopy (NERS) substrates with high reproducibility and controllability were developed. Using oxygen plasma treatment, large-area and uniformly rough polystyrene sphere (URPS) arrays in conjunction with 20 nm Au films (AuURPS) were fabricated for SERS substrates. Au nanoparticles and clusters covered the surface of the URPS arrays, and this increased the Raman signal. In the detection of malachite green (MG), the fabricated NERS substrates have high reproducibility and sensitivity. The enhancement factor (EF) of Au nanoparticles and clusters was simulated by finite-difference time-domain (FDTD) simulations and the EF was more than 104. The measured EF of our developed substrate was more than 108 with a relative standard deviation as low as 6.64%–13.84% over 15 points on the substrate. The minimum limit for the MG molecules reached 50 ng/mL. Moreover, the Raman signal had a good linear relationship with the logarithmic concentration of MG, as it ranged from 50 ng/mL to 5 μg/mL. The NERS substrates proposed in this work may serve as a promising detection scheme in chemical and biological fields.
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9
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Wang X, Zhu X, Shi H, Chen Y, Chen Z, Zeng Y, Tang Z, Duan H. Three-Dimensional-Stacked Gold Nanoparticles with Sub-5 nm Gaps on Vertically Aligned TiO 2 Nanosheets for Surface-Enhanced Raman Scattering Detection Down to 10 fM Scale. ACS APPLIED MATERIALS & INTERFACES 2018; 10:35607-35614. [PMID: 30232887 DOI: 10.1021/acsami.8b11713] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Seeking for ultrasensitive and low-cost substrates is highly demandable for practical applications of surface-enhanced Raman scattering (SERS) technology. In this work, we report an ultrasensitive SERS-active substrate based on wet-chemistry-synthesized vertically aligned large-area TiO2 nanosheets (NSs) decorated by densely packed gold nanoparticles (Au NPs) with sub-5 nm gaps. Via a multistep successive deposition process, three-dimensional-stacked Au NPs sandwiched by a 3 nm SiO2 layer were assembled onto the TiO2 NS, enabling numerous hotspots due to the formation of both ultratiny plasmonic gaps and semiconductor/metal interfaces. Experimental results show that the fabricated substrate displays a detection limit down to 10 fM (10-14 M) without involving any condensation process by using the crystal violet as probe molecules. Control experiments and electromagnetic simulations indicate that the nanogaps defined by the 3 nm spacer are essential for the obtained excellent SERS performance. With its ultrasensitive detection capability, we demonstrate that the fabricated SERS substrate can be used for the trace analysis of melamine in milk.
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Affiliation(s)
| | - Xupeng Zhu
- School of Physics Science and Technology , Lingnan Normal University , Zhanjiang 524048 , People's Republic of China
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10
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Wafer-Scale Hierarchical Nanopillar Arrays Based on Au Masks and Reactive Ion Etching for Effective 3D SERS Substrate. MATERIALS 2018; 11:ma11020239. [PMID: 29401713 PMCID: PMC5848936 DOI: 10.3390/ma11020239] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 01/27/2018] [Accepted: 01/29/2018] [Indexed: 01/02/2023]
Abstract
Two-dimensional (2D) periodic micro/nanostructured arrays as SERS substrates have attracted intense attention due to their excellent uniformity and good stability. In this work, periodic hierarchical SiO₂ nanopillar arrays decorated with Ag nanoparticles (NPs) with clean surface were prepared on a wafer-scale using monolayer Au NP arrays as masks, followed by reactive ion etching (RIE), depositing Ag layer and annealing. For the prepared SiO₂ nanopillar arrays decorated with Ag NPs, the size of Ag NPs was tuned from ca. 24 to 126 nanometers by controlling the deposition thickness of Ag film. Importantly, the SiO₂ nanopillar arrays decorated with Ag NPs could be used as highly sensitive SERS substrate for the detection of 4-aminothiophenol (4-ATP) and rhodamine 6G (R6G) due to the high loading of Ag NPs and a very uniform morphology. With a deposition thickness of Ag layer of 30 nm, the SiO₂ nanopillar arrays decorated with Ag NPs exhibited the best sensitive SERS activity. The excellent SERS performance of this substrate is mainly attributed to high-density "hotspots" derived from nanogaps between Ag NPs. Furthermore, this strategy might be extended to synthesize other nanostructured arrays with a large area, which are difficult to be prepared only via conventional wet-chemical or physical methods.
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11
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Wang H, Huo Z, Zhang Z, Chen S, Jiang S. Optimization of Ag coated hydrogen silsesquioxane square array hybrid structure design for surface-enhanced Raman scattering substrate. OPTICS EXPRESS 2018; 26:1097-1107. [PMID: 29401988 DOI: 10.1364/oe.26.001097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 01/07/2018] [Indexed: 06/07/2023]
Abstract
A computer-automated design process for a surface-enhanced Raman scattering (SERS) substrate using a particle swarm optimization algorithm is proposed. Nanostructured Ag coated hydrogen silsesquioxane nanopillar arrays of various sizes for SERS substrate applications are fabricated by direct Ag film deposition on substrates patterned by electron beam lithography and are investigated systematically. Good agreement is demonstrated between experimental and simulation results. The absorption spectra, charge distributions, and electric field distributions are calculated using finite-difference time-domain simulations to explain the field enhancement mechanism and indicate that this enhancement originates from plasmon resonance. Our work provides a guide towards optimum SERS substrate design.
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12
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Yang D, Cho H, Koo S, Vaidyanathan SR, Woo K, Yoon Y, Choo H. Simple, Large-Scale Fabrication of Uniform Raman-Enhancing Substrate with Enhancement Saturation. ACS APPLIED MATERIALS & INTERFACES 2017; 9:19092-19101. [PMID: 28452459 DOI: 10.1021/acsami.7b03239] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
It is well-known that gold nanoparticle (AuNP) clusters generate strong surface-enhanced Raman scattering (SERS). In order to produce spatially uniform Raman-enhancing substrates at a large scale, we synthesized vertically perforated three-dimensional (3D) AuNP stacks. The 3D stacks were fabricated by first hydrothermally synthesizing ZnO nanowires perpendicular to silicon wafers followed by repetitively performing liquid-phase deposition of AuNPs on the tops and side surfaces of the nanowires. During the deposition process, the nanowires were shown to gradually dissolve away, leaving hollow vestiges or perforations surrounded by stacks of AuNPs. Simulation studies and experimental measurements reveal these nanoscale perforations serve as light paths that allow the excitation light to excite deeper regions of the 3D stacks for stronger overall Raman emission. Combined with properly sized nanoparticles, this feature maximizes and saturates the Raman enhancement at 1-pM sensitivity across the entire wafer-scale substrate, and the saturation improves the wafer-scale uniformity by a factor of 6 when compared to nanoparticle layers deposited directly on a silicon wafer substrate. Using the 3D-stacked substrates, quantitative sensing of adenine molecules yielded concentrations measurements within 10% of the known value. Understanding the enhancing mechanisms and engineering the 3D stacks have opened a new method of harnessing the intense SERS observed in nanoparticle clusters and realize practical SERS substrates with significantly improved uniformity suitable for quantitative chemical sensing.
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Affiliation(s)
- Daejong Yang
- Department of Medical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Hyunjun Cho
- Department of Electrical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Sukmo Koo
- Department of Medical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Sagar R Vaidyanathan
- Department of Electrical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Kelly Woo
- Department of Electrical Engineering, California Institute of Technology , Pasadena, California 91125, United States
| | - Youngzoon Yoon
- Device Lab, Device & System Research Center, Samsung Advanced Institute of Technology (SAIT) , Suwon 16678, Republic of Korea
| | - Hyuck Choo
- Department of Medical Engineering, California Institute of Technology , Pasadena, California 91125, United States
- Department of Electrical Engineering, California Institute of Technology , Pasadena, California 91125, United States
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13
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Zheng M, Zhu X, Chen Y, Xiang Q, Duan H. Three-dimensional donut-like gold nanorings with multiple hot spots for surface-enhanced raman spectroscopy. NANOTECHNOLOGY 2017; 28:045303. [PMID: 27981948 DOI: 10.1088/1361-6528/28/4/045303] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Seeking for the best possible substrates for surface-enhanced Raman spectroscopy (SERS) is of great interest for single-molecule-level detection applications. Lithographic plasmonic nanostructures are supposed to enable uniform enhancement and thus have attracted extensive interest in the past decade. In this work, we propose and demonstrate a lithographic three-dimensional (3D) donut-like gold nanoring array as a SERS substrate with an enhancement factor (EF) up to 3.84 × 107. This 3D nanoring array could be directly fabricated using electron-beam-lithography-defined templates without any additional lift-off process and thus promises ultraclean metallic surfaces. Meanwhile, the 3D configuration allows multiple hot spots for improving SERS performance compared to planar counterparts with comparable plasmon resonance position. Systematic experiments and simulations were conducted to gain understanding of the origin of the improved SERS performance. The results imply that the 3D donut-like gold nanorings with multiple hot spots can serve as a promising configuration for SERS applications.
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Affiliation(s)
- Mengjie Zheng
- School of Electronics and Physics, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, People's Republic of China
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