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Kanjwal MA, Ghaferi AA. Advanced Waveguide Based LOC Biosensors: A Minireview. SENSORS (BASEL, SWITZERLAND) 2022; 22:5443. [PMID: 35891123 PMCID: PMC9323137 DOI: 10.3390/s22145443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 06/28/2022] [Accepted: 07/13/2022] [Indexed: 06/15/2023]
Abstract
This mini review features contemporary advances in mid-infrared (MIR) thin-film waveguide technology and on-chip photonics, promoting high-performance biosensing platforms. Supported by recent developments in MIR thin-film waveguides, it is expected that label-free assimilated MIR sensing platforms will soon supplement the current sensing technologies for biomedical diagnostics. The state-of-the-art shows that various types of waveguide material can be utilized for waveguide spectroscopic measurements in MIR. However, there are challenges to integrating these waveguide platforms with microfluidic/Lab-on-a-Chip (LOC) devices, due to poor light-material interactions. Graphene and its analogs have found many applications in microfluidic-based LOC devices, to address to this issue. Graphene-based materials possess a high conductivity, a large surface-to-volume ratio, a smaller and tunable bandgap, and allow easier sample loading; which is essential for acquiring precise electrochemical information. This work discusses advanced waveguide materials, their advantages, and disease diagnostics with MIR thin-film based waveguides. The incorporation of graphene into waveguides improves the light-graphene interaction, and photonic devices greatly benefit from graphene's strong field-controlled optical response.
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2
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Ghithan JH, Moreno M, Keynton RS, O'Toole MG, Mendes SB. Adsorption Properties and Electron-transfer Rates of a Redox Probe at Different Interfaces of an Immunoassay Assembled on an Electro-active Photonic Platform. ANAL SCI 2021; 37:1391-1399. [PMID: 33896878 DOI: 10.2116/analsci.21p010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Physical and chemical properties of a redox protein adsorbed to different interfaces of a multilayer immunoassay assembly were studied using a single-mode, electro-active, integrated optical waveguide (SM-EA-IOW) platform. For each interface of the immunoassay assembly (indium tin oxide, 3-aminopropyl triethoxysilane, recombinant protein G, antibody, and bovine serum albumin) the surface density, the adsorption kinetics, and the electron-transfer rate of bound species of the redox-active cytochrome c (Cyt-C) protein were accurately quantified at very low surface concentrations of redox species (from 0.4 to 4% of a full monolayer) using a highly sensitive optical impedance spectroscopy (OIS) technique based on measurements obtained with the SM-EA-IOW platform. The technique is shown here to provide quantitative insights into an important immunoassay assembly for characterization and understanding of the mechanisms of electron transfer rate, the affinity strength of molecular binding, and the associated bio-selectivity. Such methodology and acquired knowledge are crucial for the development of novel and advanced immuno-biosensors.
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Affiliation(s)
- Jafar H Ghithan
- Department of Physics and Astronomy, University of Louisville
| | - Monica Moreno
- Department of Bioengineering, University of Louisville
| | | | | | - Sergio B Mendes
- Department of Physics and Astronomy, University of Louisville
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3
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Ehamparam R, Oquendo LE, Liao MW, Brynnel AK, Ou KL, Armstrong NR, McGrath DV, Saavedra SS. Axially Bound Ruthenium Phthalocyanine Monolayers on Indium Tin Oxide: Structure, Energetics, and Charge Transfer Properties. ACS APPLIED MATERIALS & INTERFACES 2017; 9:29213-29223. [PMID: 28795562 DOI: 10.1021/acsami.7b07394] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The efficiency of charge collection at the organic/transparent conducting oxide (TCO) interface in organic photovoltaic (OPV) devices affects overall device efficiency. Modifying the TCO with an electrochemically active molecule may enhance OPV efficiency by providing a charge-transfer pathway between the electrode and the organic active layer, and may also mitigate surface recombination. The synthesis and characterization of phosphonic acid-ruthenium phthalocyanine (RuPcPA) monolayer films on indium tin oxide (ITO), designed to facilitate charge harvesting at ITO electrodes, is presented in this work. The PA group was installed axially relative to the Pc plane so that upon deposition, RuPcPA molecules were preferentially aligned with the ITO surface plane. The tilt angle of 22° between the normal axes to the Pc plane and the ITO surface plane, measured by attenuated total reflectance (ATR) spectroscopy, is consistent with a predominately in-plane orientation. The effect of surface roughness on RuPcPA orientation was modeled, and a correlation was obtained between experimental and theoretical mean tilt angles. Based on electrochemical and spectroelectrochemical studies, RuPcPA monolayers are composed predominately of monomers. Electrochemical impedance spectroscopy (EIS) and potential modulated-ATR (PM-ATR) spectroscopy were used to characterize the electron-transfer (ET) kinetics of these monolayers. A rate constant of 4.0 × 103 s-1 was measured using EIS, consistent with a short tunneling distance between the chromophore and the electrode surface. Using PM-ATR, ks,opt values of 2.2 × 103 and 2.4 × 103 s-1 were measured using TE and TM polarized light, respectively; the similarity of these values is consistent with a narrow molecular orientation distribution and narrow range of tunneling distances. The ionization potential of RuPcPA-modified ITO was measured using ultraviolet photoelectron spectroscopy and the results indicate favorable energetics for hole collection at the RuPcPA/ITO interface, indicating that this type of TCO modification may be useful for enhancing charge collection efficiency in OPV devices.
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Affiliation(s)
- Ramanan Ehamparam
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Luis E Oquendo
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Michael W Liao
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Ambjorn K Brynnel
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Kai-Lin Ou
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Neal R Armstrong
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - Dominic V McGrath
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
| | - S Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
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4
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Han X, Mendes SB. Electron-Transfer Rate in Potential-Modulated Redox Reactions with Electro-Active Optical Waveguides. ANAL SCI 2017; 33:435-441. [PMID: 28392516 DOI: 10.2116/analsci.33.435] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A novel methodology has been developed to determine electron-transfer rate in electrically driven redox reactions. Based on a widely adopted electrical circuit describing faradaic processes in an electrochemical cell, the approach uses a combination of impedance data from optical and electrical measurements that are simultaneously acquired in a spectroelectrochemical experiment. Once the consistency of our methodology was experimentally corroborated, it was put to practice for investigating electron-transfer rate of cytochrome c adsorbates at very low concentrations on an indium tin oxide electrode by using a highly sensitive, single-mode, electro-active, integrated optical waveguide platform. Different surface densities of redox species on the electrode interface and different ionic strengths in the electrolyte solution were studied. Higher surface densities and higher ionic strengths are shown to slow down the electron-transfer process between the redox molecules and the working electrode.
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Affiliation(s)
- Xue Han
- Department of Physics and Astronomy, University of Louisville
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5
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ZHENG Y, SAAVEDRA SS. Characterization of Charge-Transfer Kinetics at Organic/Electrode Interfaces Using Potential-modulated Attenuated Total Reflectance (PM-ATR) Spectroscopy. ANAL SCI 2017; 33:427-433. [DOI: 10.2116/analsci.33.427] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Yilong ZHENG
- Department of Chemistry & Biochemistry, University of Arizona
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6
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Schädle T, Mizaikoff B. Mid-Infrared Waveguides: A Perspective. APPLIED SPECTROSCOPY 2016; 70:1625-1638. [PMID: 27624555 DOI: 10.1177/0003702816659668] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 05/28/2023]
Abstract
Significant advancements in waveguide technology in the mid-infrared (MIR) regime during recent decades have assisted in establishing MIR spectroscopic and sensing technologies as a routine tool among nondestructive analytical methods. In this review, the evolution of MIR waveguides along with state-of-the-art technologies facilitating next-generation MIR chem/bio sensors will be discussed introducing a classification scheme defining three "generations" of MIR waveguides: (1) conventional internal reflection elements as "first generation" waveguides; (2) MIR-transparent optical fibers as "second generation" waveguides; and most recently introduced(3) thin-film structures as "third generation" waveguides. Selected application examples for these each waveguide category along with future trends will highlight utility and perspectives for waveguide-based MIR spectroscopy and sensing systems.
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Affiliation(s)
- Thomas Schädle
- Institute of Analytical and Bioanalytical Chemistry (IABC), Ulm University, Ulm, Germany
| | - Boris Mizaikoff
- Institute of Analytical and Bioanalytical Chemistry (IABC), Ulm University, Ulm, Germany
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7
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Han X, Mendes SB. Spectroelectrochemical Properties of Ultra-Thin Indium Tin Oxide Films under Electric Potential Modulation. THIN SOLID FILMS 2016; 603:230-237. [PMID: 26973359 PMCID: PMC4785843 DOI: 10.1016/j.tsf.2016.02.018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
In this work, the spectroscopic properties of ultra-thin ITO films are characterized under an applied electric potential modulation. To detect minute spectroscopic features, the ultra-thin ITO film was coated over an extremely sensitive single-mode integrated optical waveguide, which provided a long pathlength with more than adequate sensitivity for optical interrogation of the ultra-thin film. Experimental configurations with broadband light and several laser lines at different modulation schemes of an applied electric potential were utilized to elucidate the nature of intrinsic changes. The imaginary component of the refractive index (absorption coefficient) of the ultra-thin ITO film is unequivocally shown to have a dependence on the applied potential and the profile of this dependence changes substantially even for wavelengths inside a small spectral window (500-600 nm). The characterization technique and the data reported here can be crucial to several applications of the ITO material as a transparent conductive electrode, as for example in spectroelectrochemical investigations of surface-confined redox species.
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Affiliation(s)
- Xue Han
- Department of Physics and Astronomy, University of Louisville, Louisville, KY, 40208
| | - Sergio B Mendes
- Department of Physics and Astronomy, University of Louisville, Louisville, KY, 40208
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8
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Han X, Mendes SB. Optical impedance spectroscopy with single-mode electro-active-integrated optical waveguides. Anal Chem 2014; 86:1468-77. [PMID: 24417718 PMCID: PMC3983008 DOI: 10.1021/ac4030736] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An optical impedance spectroscopy (OIS) technique based on a single-mode electro-active-integrated optical waveguide (EA-IOW) was developed to investigate electron-transfer processes of redox adsorbates. A highly sensitive single-mode EA-IOW device was used to optically follow the time-dependent faradaic current originated from a submonolayer of cytochrome c undergoing redox exchanges driven by a harmonic modulation of the electric potential at several dc bias potentials and at several frequencies. To properly retrieve the faradaic current density from the ac-modulated optical signal, we introduce here a mathematical formalism that (i) accounts for intrinsic changes that invariably occur in the optical baseline of the EA-IOW device during potential modulation and (ii) provides accurate results for the electro-chemical parameters. We are able to optically reconstruct the faradaic current density profile against the dc bias potential in the working electrode, identify the formal potential, and determine the energy-width of the electron-transfer process. In addition, by combining the optically reconstructed faradaic signal with simple electrical measurements of impedance across the whole electrochemical cell and the capacitance of the electric double-layer, we are able to determine the time-constant connected to the redox reaction of the adsorbed protein assembly. For cytochrome c directly immobilized onto the indium tin oxide (ITO) surface, we measured a reaction rate constant of 26.5 s(-1). Finally, we calculate the charge-transfer resistance and pseudocapacitance associated with the electron-transfer process and show that the frequency dependence of the redox reaction of the protein submonolayer follows as expected the electrical equivalent of an RC-series admittance diagram. Above all, we show here that OIS with single-mode EA-IOW's provide strong analytical signals that can be readily monitored even for small surface-densities of species involved in the redox process (e.g., fmol/cm(2), 0.1% of a full protein monolayer). This experimental approach, when combined with the analytical formalism described here, brings additional sensitivity, accuracy, and simplicity to electro-chemical analysis and is expected to become a useful tool in investigations of redox processes.
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Affiliation(s)
- Xue Han
- Department of Physics and Astronomy, University of Louisville , Louisville, Kentucky 40292, United States
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9
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Lin HC, Polaske NW, Oquendo LE, Gliboff M, Knesting KM, Nordlund D, Ginger DS, Ratcliff EL, Beam BM, Armstrong NR, McGrath DV, Saavedra SS. Electron-Transfer Processes in Zinc Phthalocyanine-Phosphonic Acid Monolayers on ITO: Characterization of Orientation and Charge-Transfer Kinetics by Waveguide Spectroelectrochemistry. J Phys Chem Lett 2012; 3:1154-1158. [PMID: 26288050 DOI: 10.1021/jz3002426] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Using a monolayer of zinc phthalocyanine (ZnPcPA) tethered to indium tin oxide (ITO) as a model for the donor/transparent conducting oxide (TCO) interface in organic photovoltaics (OPVs), we demonstrate the relationship between molecular orientation and charge-transfer rates using spectroscopic, electrochemical, and spectroelectrochemical methods. Both monomeric and aggregated forms of the phthalocyanine (Pc) are observed in ZnPcPA monolayers. Potential-modulated attenuated total reflectance (PM-ATR) measurements show that the monomeric subpopulation undergoes oxidation/reduction with ks,app = 2 × 10(2) s(-1), independent of Pc orientation. For the aggregated ZnPcPA, faster orientation-dependent charge-transfer rates are observed. For in-plane-oriented Pc aggregates, ks,app = 2 × 10(3) s(-1), whereas for upright Pc aggregates, ks,app = 7 × 10(2) s(-1). The rates for the aggregates are comparable to those required for redox-active interlayer films at the hole-collection contact in organic solar cells.
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Affiliation(s)
- Hsiao-Chu Lin
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Nathan W Polaske
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Luis E Oquendo
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | | | | | - Dennis Nordlund
- #Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Road MS69, Menlo Park, California 94025, United States
| | | | - Erin L Ratcliff
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Brooke M Beam
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Neal R Armstrong
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Dominic V McGrath
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - S Scott Saavedra
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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10
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Nicoletta FP, Cupelli D, Formoso P, De Filpo G, Colella V, Gugliuzza A. Light responsive polymer membranes: a review. MEMBRANES 2012; 2:134-97. [PMID: 24957966 PMCID: PMC4021883 DOI: 10.3390/membranes2010134] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 02/04/2012] [Accepted: 02/16/2012] [Indexed: 12/04/2022]
Abstract
In recent years, stimuli responsive materials have gained significant attention in membrane separation processes due to their ability to change specific properties in response to small external stimuli, such as light, pH, temperature, ionic strength, pressure, magnetic field, antigen, chemical composition, and so on. In this review, we briefly report recent progresses in light-driven materials and membranes. Photo-switching mechanisms, valved-membrane fabrication and light-driven properties are examined. Advances and perspectives of light responsive polymer membranes in biotechnology, chemistry and biology areas are discussed.
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Affiliation(s)
| | - Daniela Cupelli
- Department of Pharmaceutical Sciences, Università della Calabria, I-87036 Rende (CS), Italy.
| | - Patrizia Formoso
- Department of Pharmaceutical Sciences, Università della Calabria, I-87036 Rende (CS), Italy.
| | - Giovanni De Filpo
- Department of Chemistry, Università della Calabria, I-87036 Rende (CS), Italy.
| | - Valentina Colella
- Department of Pharmaceutical Sciences, Università della Calabria, I-87036 Rende (CS), Italy.
| | - Annarosa Gugliuzza
- Institute on Membrane Technology-National Council Research, ITM-CNR, I-87030 Rende (CS), Italy.
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11
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Ge C, Orosz KS, Armstrong NR, Saavedra SS. Poly(aniline) nanowires in sol-gel coated ITO: a pH-responsive substrate for planar supported lipid bilayers. ACS APPLIED MATERIALS & INTERFACES 2011; 3:2677-85. [PMID: 21707069 PMCID: PMC3145051 DOI: 10.1021/am2004637] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Facilitated ion transport across an artificial lipid bilayer coupled to a solid substrate is a function common to several types of bioelectronic devices based on supported membranes, including biomimetic fuel cells and ion channel biosensors. Described here is fabrication of a pH-sensitive transducer composed of a porous sol-gel layer derivatized with poly(aniline) (PANI) nanowires grown from an underlying planar indium-tin oxide (ITO) electrode. The upper sol-gel surface is hydrophilic, smooth, and compatible with deposition of a planar supported lipid bilayer (PSLB) formed via vesicle fusion. Conducting tip AFM was used to show that the PANI wires are connected to the ITO, which convert this electrode into a potentiometric pH sensor. The response to changes in the pH of the buffer contacting the PANI nanowire/sol-gel/ITO electrode is blocked by the very low ion permeability of the overlying fluid PSLB. The feasibility of using this assembly to monitor facilitated proton transport across the PSLB was demonstrated by doping the membrane with lipophilic ionophores that respond to a transmembrane pH gradient, which produced an apparent proton permeability several orders of magnitude greater than values measured for undoped lipid bilayers.
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Affiliation(s)
- Chenhao Ge
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - Kristina S. Orosz
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - Neal R. Armstrong
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry University of Arizona Tucson, AZ 85721-0041
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12
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Simon AM, Marucci NE, Saavedra SS. Measuring Photochemical Kinetics in Submonolayer Films by Transient ATR Spectroscopy on a Multimode Planar Waveguide. Anal Chem 2011; 83:5762-6. [DOI: 10.1021/ac2011526] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Anne M. Simon
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - Nicole E. Marucci
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
| | - S. Scott Saavedra
- Department of Chemistry and Biochemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, United States
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13
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Pereira MB, Craven JS, Mendes SB. Solid immersion lens at the aplanatic condition for enhancing the spectral bandwidth of a waveguide grating coupler. OPTICAL ENGINEERING (REDONDO BEACH, CALIF.) 2010; 49:124601. [PMID: 21572934 PMCID: PMC3092502 DOI: 10.1117/1.3520063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report a technique to substantially boost the spectral bandwidth of a conventional waveguide grating coupler by using a solid immersion cylindrical lens at the aplanatic condition to create a highly anamorphic beam and reach a much larger numerical aperture, thus enhancing the spectral bandwidth of a free-space propagating optical beam coupled into a single-mode planar integrated optical waveguide (IOW). Our experimental results show that the broadband IOW spectrometer thus created almost doubles (94% enhancement) the coupled spectral bandwidth of a conventional configuration. To exemplify the benefits made possible by the developed approach, we applied the technique to the broadband spectroscopic characterization of a protein submonolayer; our experimental data confirm the enhanced spectral bandwidth (around 380-nm) and illustrate the potentials of the developed technology. Besides the enhanced bandwidth, the broadband coupler of the single-mode IOW spectrometer described here is more robust and user-friendly than those previously reported in the literature and is expected to have an important impact on spectroscopic studies of surface-adsorbed molecular layers and surface phenomena.
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Affiliation(s)
- Marcelo B. Pereira
- Instituto de Física, UFRGS, CP 15051, Porto Alegre, RS 91501-970, Brazil
| | - Jill S. Craven
- California Institute of Technology, Department of Chemical Engineering, Pasadena, California 91125
| | - Sergio B. Mendes
- University of Louisville, Department of Physics and Astronomy, Louisville, Kentucky 40292
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14
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Ratcliff EL, Veneman PA, Simmonds A, Zacher B, Huebner D, Saavedra SS, Armstrong NR. A planar, chip-based, dual-beam refractometer using an integrated organic light-emitting diode (OLED) light source and organic photovoltaic (OPV) detectors. Anal Chem 2010; 82:2734-42. [PMID: 20218580 DOI: 10.1021/ac9026109] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We present a simple chip-based refractometer with a central organic light-emitting diode (OLED) light source and two opposed organic photovoltaic (OPV) detectors on an internal reflection element (IRE) substrate, creating a true dual-beam sensor platform. For first-generation platforms, we demonstrate the use of a single heterojunction OLED based on electroluminescence from an Alq(3)/TPD heterojunction (tris-(8-hydroxyquinoline)aluminum/N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine) and light detection with planar heterojunction pentacene/C(60) OPVs. The sensor utilizes the considerable fraction of emitted light from conventional thin-film OLEDs that is coupled into guided modes in the IRE, instead of into the forward (display) direction. A ray-optics description is used to describe light throughput and efficiency-limiting factors for light coupling from the OLED into the substrate modes, light traversing through the IRE substrate, and light coupling into the OPV detectors. The arrangement of the OLED at the center of the chip provides for two sensing regions: a "sample" channel and a "reference" channel, with detection of light by independent OPV detectors. This configuration allows for normalization of the sensor response against fluctuations in OLED light output, stability, and local fluctuations (temperature) that might influence sensor response. The dual-beam configuration permits significantly enhanced sensitivity to refractive index changes, relative to single-beam protocols, and is easily integrated into a field-portable instrumentation package. Changes in refractive index (DeltaRI) between 10(-2) and 10(-3) RI units could be detected for single beam operation, with sensitivity increased to DeltaRI approximately 10(-4) RI units when the dual-beam configuration is employed.
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Affiliation(s)
- Erin L Ratcliff
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
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15
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Broadband Spectroelectrochemical Interrogation of Molecular Thin Films by Single-Mode Electro-Active Integrated Optical Waveguides. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-3-540-88242-8_4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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16
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Beam BM, Armstrong NR, Mendes SB. An electroactive fiber optic chip for spectroelectrochemical characterization of ultra-thin redox-active films. Analyst 2009; 134:454-9. [DOI: 10.1039/b814338b] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Subramaniam V, D'Ambruoso GD, Hall HK, Wysocki RJ, Brown MF, Saavedra SS. Reconstitution of rhodopsin into polymerizable planar supported lipid bilayers: influence of dienoyl monomer structure on photoactivation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:11067-75. [PMID: 18759470 PMCID: PMC2726791 DOI: 10.1021/la801835g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
G-protein-coupled receptors (GPCRs) play key roles in cellular signal transduction and many are pharmacologically important targets for drug discovery. GPCRs can be reconstituted in planar supported lipid bilayers (PSLBs) with retention of activity, which has led to development of GPCR-based biosensors and biochips. However, PSLBs composed of natural lipids lack the high stability desired for many technological applications. One strategy is to use synthetic lipid monomers that can be polymerized to form robust bilayers. A key question is how lipid polymerization affects GPCR structure and activity. Here we have investigated the photochemical activity of bovine rhodopsin (Rho), a model GPCR, reconstituted into PSLBs composed of lipids having one or two polymerizable dienoyl moieties located in different regions of the acyl chains. Plasmon waveguide resonance spectroscopy was used to compare the degree of Rho photoactivation in fluid and poly(lipid) PSLBs. The position of the dienoyl moiety was found to have a significant effect: polymerization near the glycerol backbone significantly attenuates Rho activity whereas polymerization near the acyl chain termini does not. Differences in cross-link density near the acyl chain termini also do not affect Rho activity. In unpolymerized PSLBs, an equimolar mixture of phosphatidylethanolamine and phosphatidylcholine (PC) lipids enhances activity relative to pure PC; however after polymerization, the enhancement is eliminated which is attributed to stabilization of the membrane lamellar phase. These results should provide guidance for the design of robust lipid bilayers functionalized with transmembrane proteins for use in membrane-based biochips and biosensors.
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Affiliation(s)
- Varuni Subramaniam
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | | | - H. K. Hall
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - Ronald J. Wysocki
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - Michael F. Brown
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
| | - S. Scott Saavedra
- Department of Chemistry, University of Arizona, Tucson, Arizona, 85721-0041
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Hotta H, Tatsuno K, Hattori Y, Hashimoto T, Uehara M, Tsunoda KI. In situ monitoring of the H+ concentration change near an electrode surface through electrolysis using slab optical waveguide pH sensor. Electrochem commun 2008. [DOI: 10.1016/j.elecom.2008.07.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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19
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Li J, Wang L, Liu J, Evmenenko G, Dutta P, Marks TJ. Characterization of transparent conducting oxide surfaces using self-assembled electroactive monolayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:5755-5765. [PMID: 18457433 DOI: 10.1021/la704038g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The electronic properties of various transparent conducting oxide (TCO) surfaces are probed electrochemically via self-assembled monolayers (SAMs). A novel graftable probe molecule having a tethered trichlorosilyl group and a redox-active ferrocenyl functionality (Fc(CH2) 4SiCl3) is synthesized for this purpose. This molecule can be self-assembled via covalent bonds to form monolayers on various TCO surfaces. On as-received ITO, saturation coverage of 6.6 x 10(-10) mol/cm2 by a close-packed monolayer and an electron-transfer rate of 6.65 s(-1) is achieved after 9 h of chemisorption, as determined by cyclic voltammetry (CV) and synchrotron X-ray reflectivity. With this molecular probe, it is found that O2 plasma-treated ITO has a significantly greater electroactive coverage of 7.9 x 10 (-10) mol/cm2 than as-received ITO. CV studies of this redox SAM on five different TCO surfaces reveal that MOCVD-derived CdO exhibits the greatest electroactive coverage (8.1 x 10(-10) mol/cm2) and MOCVD-derived ZITO (ZnIn2.0Sn1.5O) exhibits the highest electron transfer rate (7.12 s(-1)).
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Affiliation(s)
- Jianfeng Li
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
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Time-resolved evanescent wave absorption spectroscopy for real-time monitoring of heme protein adsorption to glass. Anal Biochem 2008; 374:196-202. [DOI: 10.1016/j.ab.2007.10.013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Revised: 10/10/2007] [Accepted: 10/11/2007] [Indexed: 11/20/2022]
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21
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Zhang N, Schweiss R, Zong Y, Knoll W. Electrochemical surface plasmon spectroscopy—Recent developments and applications. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2006.10.060] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Ge C, Armstrong NR, Saavedra SS. pH-Sensing Properties of Poly(aniline) Ultrathin Films Self-Assembled on Indium−Tin Oxide. Anal Chem 2007; 79:1401-10. [PMID: 17297939 DOI: 10.1021/ac061740e] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structural and functional properties of ultrathin (<5 nm) poly(aniline) (PANI) films deposited on indium-tin oxide (ITO) have been investigated using electrochemical and attenuated total reflection (ATR) spectroscopy methods. Layer-by-layer (LbL) self-assembly was used to form films composed of one and two bilayers of PANI and poly(acrylic acid) (PAA), as well as single PANI layers of approximately monolayer thickness. PANI deposited on an ITO electrode is electroactive at neutral pH, both with and without codeposition of an acid dopant such as PAA. In the absence of PAA, it is hypothesized that the acidic surface groups on ITO can function as the counterion. The pH response of PANI single layer, (PANI/PAA)(1), and (PANI/PAA)(2) films was examined using both potentiometry and ATR spectroscopy. Near-Nernstian potentiometric responses over pH 3-9 were observed for all three types of films, consistent with the weak acid-base behavior expected of polymers assembled in a LbL film. The ATR spectral sensitivity to pH increases as the number of layers in the film increases, with the highest sensitivity achieved by monitoring the absorbance at 800 nm (predominately due to the emeraldine salt form) of (PANI/PAA)(2) films. Codeposition of PANI and PAA appears to produce a wide distribution of strengths of acidic and basic sites in the film and thus a large linear dynamic range, up to six pH units. The water contact angle of (PANI/PAA)(2) is approximately 16 degrees, which is considerably more hydrophilic than either the PANI single layer or (PANI/PAA)(1) films ( approximately 40 degrees ). This film is shown to be a suitable substrate for deposition of a planar supported phospholipid bilayer. The supported membrane is highly impermeable to protons, which makes this architecture useful for monitoring transmembrane charge transport.
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Affiliation(s)
- Chenhao Ge
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041, USA
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23
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Takahashi H, Fujita K, Ohno H. Direct Visible Spectral Analysis of Solid Samples by Optical Waveguide Spectroscopy due to Adsorbed Sample Molecules after Sublimation. CHEM LETT 2007. [DOI: 10.1246/cl.2007.116] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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24
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Takeuchi T, Akeda K, Murakami S, Shinmori H, Inoue S, Lee WS, Hishiya T. Photoresponsive porphyrin-imprinted polymers prepared using a novel functional monomer having diaminopyridine and azobenzene moieties. Org Biomol Chem 2007; 5:2368-74. [PMID: 17637955 DOI: 10.1039/b704830k] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel photoresponsive functional monomer bearing diaminopyridine and azobenzene moieties was synthesized and applied to the preparation of photo-regulated molecularly imprinted polymers, which can recognize porphyrin derivatives through hydrogen bonding. The binding affinity of the imprinted cavities was regulated by UV irradiation, suggesting that azobenzene groups located inside the binding sites worked as photosensitizers and the trans-cis isomerization could regulate the affinity for the target compounds. Repetitive binding of the target compound to trans-IP and cis-IP was directly monitored by slab optical waveguide spectroscopy and the photo-mediated regulation of binding affinity was successfully confirmed.
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Affiliation(s)
- Toshifumi Takeuchi
- Graduate School of Science and Technology, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan.
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25
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Ayato Y, Takatsu A, Kato K, Matsuda N. Identification of adsorption states of heptyl viologen cation radicals in a thin deposition layer by slab optical waveguide spectroscopy utilizing indium-tin-oxide electrodes. J Electroanal Chem (Lausanne) 2006. [DOI: 10.1016/j.jelechem.2006.06.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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26
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Xu J, Bowden EF. Determination of the Orientation of Adsorbed Cytochrome c on Carboxyalkanethiol Self-Assembled Monolayers by In Situ Differential Modification. J Am Chem Soc 2006; 128:6813-22. [PMID: 16719461 DOI: 10.1021/ja054219v] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The contact domain utilized by horse cytochrome c when adsorptively bound to a C(10)COOH self-assembled monolayer (SAM) was delineated using a chemical method based on differential modification of surface amino acids. Horse cytochrome c was adsorbed at low ionic strength (pH 7.0, 4.4 mM potassium phosphate) onto 10 microm diameter gold particles coated with HS(CH(2))(10)COOH SAMs. After in situ modification of lysyl groups by reductive Schiff-base methylation, the protein was desorbed, digested using trypsin, and the peptide mapped using LC/MS. Relative lysyl reactivities were ascertained by comparing the resulting peptide frequencies to control samples of solution cytochrome c modified to the same average extent. The least reactive lysines in adsorbed cytochrome c were found to be 13, 72, 73, 79, and 86-88, consistent with a contact region located up and to the left (Met-80 side) of the solvent-exposed heme edge (conventional front face view). The most reactive lysines were 39, 53, 55, and 60, located on the lower backside. The proposed orientation features a heme tilt angle of approximately 35-40 degrees with respect to the substrate surface normal. Factors that can complicate or distort data interpretation are discussed, and the generality of differential modification relative to existing in situ methods for protein orientation determination is also addressed.
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Affiliation(s)
- Jishou Xu
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
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Runge AF, Mendes SB, Saavedra SS. Order Parameters and Orientation Distributions of Solution Adsorbed and Microcontact Printed Cytochrome c Protein Films on Glass and ITO. J Phys Chem B 2006; 110:6732-9. [PMID: 16570979 DOI: 10.1021/jp056049e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of solution adsorbed and microcontact printed (muCP) cytochrome c (cyt c) films on glass and indium tin oxide (ITO) was investigated using attenuated total reflectance (ATR) and total internal reflectance fluorescence (TIRF) spectroscopies to determine the orientation of the heme groups in the films. The second and fourth order parameters of the heme as well as information on the angle between the absorption and emission dipoles of the heme, gamma, were experimentally determined. The order parameters of the heme are related to the order parameters of the protein molecule using the known angle between the heme plane and the electrostatic dipole moment of the cyt c protein. The effect of the surface roughness of the substrates (glass and ITO) was also taken into account quantitatively using AFM data. Physically possible order parameters were obtained for the heme group in both solution adsorbed and muCP films, but not for the electrostatic dipole moment of the protein. In addition, the experimental values of {cos2 gamma} for immobilized zinc-substituted cyt c are greater than the values of {cos2 gamma} determined in viscous solutions, which could be an indication that the environment of the heme groups changes upon adsorption. The electron transfer behavior of solution adsorbed and muCP films on ITO, determined using electrochemical methods, is compared to their orientation distribution and surface coverage as determined by spectroscopic methods.
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Affiliation(s)
- Anne F Runge
- Department of Chemistry and College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA
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Polizzi MA, Plocinik RM, Simpson GJ. Ellipsometric Approach for the Real-Time Detection of Label-Free Protein Adsorption by Second Harmonic Generation. J Am Chem Soc 2004; 126:5001-7. [PMID: 15080706 DOI: 10.1021/ja031627v] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Second harmonic generation (SHG) was performed using a novel ellipsometric detection approach to selectively probe the real-time surface binding kinetics of an unlabeled protein. The coherence of nonlinear optical processes introduces new possibilities for exploiting polarization that are unavailable with incoherent methods, such as absorbance and fluorescence. Adsorption of bovine serum albumin (BSA) at silica/aqueous solution interfaces resulted in changes in the polarization state of the frequency-doubled light through weak, dynamic interactions with a coadsorbed nonlinear optical probe molecule (rhodamine 6G). Using a remarkably simple instrumental approach, signals arising exclusively from surface interactions with BSA were spatially isolated and selectively detected with high signal-to-noise. The relative intensities acquired during the kinetics experiments using both circularly and linearly polarized incident beams were in excellent agreement with the responses predicted from SHG ellipsometry polarization measurements. Analysis of the polarization-dependent SHG generated during BSA adsorption at glass/aqueous solution interfaces provided direct evidence for slow conformational changes within the protein layer after adsorption, consistent with protein denaturation. This polarization selection approach is sufficiently general to be easily extended to virtually all coherent nonlinear optical processes and a variety of different surface interactions and architectures.
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Affiliation(s)
- Mark A Polizzi
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, USA
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31
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Qi ZM, Matsuda N, Takatsu A, Kato K. In situ investigation of coadsorption of myoglobin and methylene blue to hydrophilic glass by broadband time-resolved optical waveguide spectroscopy. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:778-784. [PMID: 15773105 DOI: 10.1021/la035522h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Recently, we have developed a broadband optical waveguide (OWG) spectrometer by using commercially available glass plates of tens of micrometers in thickness as the substrate-free multimode waveguides (Qi et al. Opt. Lett. 2002, 27, 2001-2003). The spectrometer having a bandwidth from 360 to 800 nm is capable of simultaneously detecting the Soret-band absorption of heme proteins and the visible absorption of organic dyes. In this article, the spectrometer was used to in situ investigate coadsorption of methylene blue (MB) and myoglobin from the mixed aqueous solution onto bare glass. Both MB and myoglobin in the mixed solution are positively charged, which makes them not only avoid the chemical interaction between each other but also easy to adsorb to hydrophilic glass. It was found that the coadsorption of MB and myoglobin occurred just in the early stage and the glass surface was finally occupied by myoglobin. The OWG spectroscopic investigation into the respective MB and myoglobin adsorptions shows that MB adsorption is reversible to some degree but that of myoglobin is irreversible. It reveals that the electrostatic binding of myoglobin to bare glass is stronger than the case of MB. Therefore, the adsorbed MB can be substituted by myoglobin. Moreover, via the electrostatic repulsion the tightly immobilized myoglobin prevents bulk MB from occupying the empty surface sites. It is the reason MB is absent from the hydrophilic glass coated with a submonolayer of myoglobin. In the article, we explained both the strong dimerization of MB at the interface and a slow decrease with time of the Soret-band absorbance after its maximum was reached. We also estimated the myoglobin coverage based on the waveguide theory. The study shows the distinguished applicability of the broadband OWG spectroscopy for in situ, real-time monitoring of the dye-protein coadsorption to silica from the mixed solution.
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Affiliation(s)
- Zhi-Mei Qi
- Nanoarchitectonics Research Center, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8565, Japan
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Mendes SB, Bradshaw JT, Saavedra SS. Technique for determining the angular orientation of molecules bound to the surface of an arbitrary planar optical waveguide. APPLIED OPTICS 2004; 43:70-78. [PMID: 14714646 DOI: 10.1364/ao.43.000070] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A technique to determine the angular orientation of a molecular assembly bound to the surface of a planar optical waveguide of arbitrary structure is described. The approach is based on measuring the absorption dichroic ratio by using the waveguide evanescent fields with orthogonal polarizations (TE, TM) and the same mode order to probe two molecular assemblies, (i) a reference sample composed of an isotropic orientation distribution of dipoles and (ii) a sample of interest. The isotropic sample is used to characterize the waveguide structure, which then allows the orientation parameters of a molecular assembly under investigation to be determined from a measured dichroic ratio. The method developed here is particularly important for applications in gradient-index and multilayer planar waveguide platforms because in those cases the extension of previously reported approaches would require a full experimental characterization of the guiding structure, which would be problematic and may yield inaccurate results.
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Affiliation(s)
- Sergio B Mendes
- Department of Chemistry, University of Arizona, 1306 East University Boulevard, Tucson, Arizona 85721, USA.
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