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Chen Y, Leung A, Wang Y, Archer NK. Optimization and Validation of an FTIR-based, All-in-one System for Viable MDR Bacteria Detection in Combat-related Wound Infection. Mil Med 2024:usae068. [PMID: 38516949 DOI: 10.1093/milmed/usae068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Revised: 02/08/2024] [Accepted: 02/18/2024] [Indexed: 03/23/2024] Open
Abstract
INTRODUCTION The U.S. Military members experiencing combat-related injuries have a higher chance of developing infections by multidrug-resistant (MDR) bacteria at admission to military hospitals. MDR wound infections result in higher amputation rates and greater risks for subsequent or chronic infections that require readmission or extended stay in the hospital. Currently, there is no FDA-clear, deployable early diagnostic system for suitable field use.We are reporting our efforts to improve a previously developed Rapid Label-free Pathogen Identification (RAPID) system to detect viable MDR bacteria in wound infections and perform antibiotic susceptibility testing (AST). Specifically, we added multiplex and automation capability and significantly simplified the sample preparation process. A functional prototype of the improved system was built, and its performance was validated using a variety of lab-prepared spiked samples and real-world samples. MATERIALS AND METHODS To access the baseline performance of the improved RAPID system in detecting bacteria presence, we selected 17 isolates, most of them from blood or wound infections, and prepared mono-strain spiked samples at 104 to 106 cfu/mL concentration. These samples were processed and analyzed by the RAPID system. To demonstrate the AST capability of the system, we selected 6 strains against 6 different antibiotics and compared the results from the system with the ones from the gold standard method.To validate the system's performance with real-world samples, we first investigated its performance on 3 swab samples from epicutaneous methicillin-resistant Staphylococcus aureus-exposed mouse model. The AST results from our system were compared with the ones from the gold standard method. All animal experiments were approved by the Johns Hopkins University Animal Care and Use Committee (Protocol No. MO21M378). Then, we obtained swab samples from 7 atopic dermatitis (AD) patients and compared our AST results with the ones from the gold standard method. The human subject protocol was approved by the Johns Hopkins Medicines Institutional Review Boards (Study No. CR00043438/IRB00307926) and by USAMRDC (Proposal Log Number/Study Number 20000251). RESULTS High-quality data were obtained from the spiked samples of all 17 strains. A quantitative analysis model built using these data achieved 94% accuracy in predicting the species ID in 8 unknown samples. The AST results on the spiked samples had shown 100% matching with the gold standard method. Our system successfully detects the presence/absence of viable bacteria in all 3 mouse and 7 AD patient swab samples. Our system shows 100% and 85.7% (6 out of 7) accuracy when compared to the oxacillin susceptibility testing results for the mouse and the AD patient swabs, respectively. CONCLUSIONS Our system has achieved excellent performance in detecting viable bacteria presence and in performing AST in a multiplex, automated, and easy-to-operate manner, on both lab-prepared and real samples. Our results have shown a path forward to a rapid (sample-to-answer time ≤3 hours), accurate, sensitive, species-specific, and portable system to detect the presence of MDR combat-related wound infections in the field environment. Our future efforts involve ruggedizing the RAPID system and evaluating performance under relevant environmental conditions.
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Affiliation(s)
- Ying Chen
- Optowares, Inc., Woburn, MA 01801, USA
| | | | - Yulia Wang
- Department of Dermatology, Johns Hopkins School of Medicine, Baltimore, MD 21231, USA
| | - Nathan K Archer
- Department of Dermatology, Johns Hopkins School of Medicine, Baltimore, MD 21231, USA
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Electroless Deposits of ZnO and Hybrid ZnO/Ag Nanoparticles on Mg-Ca0.3 Alloy Surface: Multiscale Characterization. COATINGS 2022. [DOI: 10.3390/coatings12081109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
ZnO and hybrid of ZnO/Ag structures in the nanometer size were electroless deposited on the Mg-Ca0.3 alloy surface, achieved from aqueous solutions (10−3 M at 21 °C) of ZnO (suspension), Zn(NO3)2 and AgNO3. The surface characterization of the deposits was carried out by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-Ray Photoelectron Spectroscopy (XPS), Fourier transform infrared (FTIR), UV-Visible and Raman spectroscopy. The nanoparticles (NPs) area size distribution analysis revealed that the average of ZnO-NPs was ~85 nm. Likewise, the Ag-NPs of electroless deposits had an average area size of ~100 nm and nucleated in the vicinity of ZnO-NPs as Ag+ ions have been attracted by the negatively charged O2− atoms of the Zn-O dipole. The ZnO-NPs had the wurtzite structure, as indicated by Raman spectroscopy analysis and XRD complementary analysis. The UV-Visible spectroscopy analysis gave a peak at ~320 nm associated with the decrease in the imaginary part (k) of the refractive index of Ag-NPs. On the Mg-Ca0.3 surface, MgO, Mg(OH)2 and MgCO3 are present due to the Mg-matrix. XRD spectra of Ag-NPs indicated the presence of planes arranged with the FCC hexagonal structure. The reported hybrid ZnO/Ag electroless deposits of NPs are of interest for temporary implant devices, providing antibacterial properties to Mg-Ca0.3 surface, a widely used biodegradable material.
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Rapid, label-free pathogen identification system for multidrug-resistant bacterial wound infection detection on military members in the battlefield. PLoS One 2022; 17:e0267945. [PMID: 35511776 PMCID: PMC9070933 DOI: 10.1371/journal.pone.0267945] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Accepted: 04/19/2022] [Indexed: 12/24/2022] Open
Abstract
US military service members experiencing combat-related wounds have higher risk of infection by multidrug-resistant bacteria. The gold standard culture-based antimicrobial susceptibility testing (AST) is not feasible in the battlefield environment. Thus, a rapid deployable system for bacteria identification and AST directly from wound sample is urgently needed. We report the potential of a Rapid, Label-free Pathogen Identification (RAPID) diagnostic system based on ATR-FTIR method to detect and distinguish multi-drug resistant strains for six different species in the ESKAPEE group. Our RAPID system combines sample processing on-broad to isolate and enrich bacteria cells from wound sample, ATR-FTIR measurement to detect antimicrobial-induced bacterial cell spectral changes, and machine learning model for automated, objective, and quantitative spectral analysis and unknown sample classification. Based on experimental results, our RAPID system is a promising technology for label-free, sensitive (104 cfu/mL from mixture), species-specific (> 95% accuracy), rapid (< 10 min for identification, ~ 4 hours for AST) bacteria detection directly from wound samples.
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Huang SC, Bao YF, Wu SS, Huang TX, Sartin MM, Wang X, Ren B. Electrochemical Tip-Enhanced Raman Spectroscopy: An In Situ Nanospectroscopy for Electrochemistry. Annu Rev Phys Chem 2021; 72:213-234. [PMID: 33400554 DOI: 10.1146/annurev-physchem-061020-053442] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Revealing the intrinsic relationships between the structure, properties, and performance of the electrochemical interface is a long-term goal in the electrochemistry and surface science communities because it could facilitate the rational design of electrochemical devices. Achieving this goal requires in situ characterization techniques that provide rich chemical information and high spatial resolution. Electrochemical tip-enhanced Raman spectroscopy (EC-TERS), which provides molecular fingerprint information with nanometer-scale spatial resolution, is a promising technique for achieving this goal. Since the first demonstration of this technique in 2015, EC-TERS has been developed for characterizing various electrochemical processes at the nanoscale and molecular level. Here, we review the development of EC-TERS over the past 5 years. We discuss progress in addressing the technical challenges, including optimizing the EC-TERS setup and solving tip-related issues, and provide experimental guidelines. We also survey the important applications of EC-TERS for probing molecular protonation, molecular adsorption, electrochemical reactions, and photoelectrochemical reactions. Finally, we discuss the opportunities and challenges in the future development of this young technique.
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Affiliation(s)
- Sheng-Chao Huang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Yi-Fan Bao
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Si-Si Wu
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Teng-Xiang Huang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Matthew M Sartin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Xiang Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
| | - Bin Ren
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China; ,
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5
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Broadhead EJ, Monroe A, Tibbetts KM. Deposition of Cubic Copper Nanoparticles on Silicon Laser-Induced Periodic Surface Structures via Reactive Laser Ablation in Liquid. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:3740-3750. [PMID: 33740377 DOI: 10.1021/acs.langmuir.1c00238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report the deposition of cubic copper nanoparticles (Cu NPs) of varying size and particle density on silicon laser-induced periodic surface structures via reactive laser ablation in liquid (RLAL) using intense femtosecond laser pulses. Two syntheses were compared: (1) simultaneous deposition, wherein a silicon wafer was laser-processed in aqueous Cu(NO3)2 solution and (2) sequential deposition, wherein the silicon wafer was laser-processed in water and then exposed to aqueous Cu(NO3)2. Only simultaneous deposition resulted in high Cu loading and cubic Cu NPs deposited on the surface. The solution pH, Cu(NO3)2 concentration, and sample translation rate were varied to determine their effects on the size, morphology, and density of Cu NPs. Solution pH near ∼6.8 maximized Cu deposition. The Cu(NO3)2 concentration affected the Cu NP morphology but not the size or Cu loading. The sample translation rate most significantly affected the Cu loading, particle size, and particle density. The observed synthesis parameter dependence of these Cu NP properties resembles results by electrodeposition to grow Cu NPs on silicon surfaces, which suggests that Cu NP deposition by RLAL follows a mechanism similar to electrodeposition.
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Affiliation(s)
- Eric J Broadhead
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Avery Monroe
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Katharine Moore Tibbetts
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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Bartolomeo GL, Goubert G, Zenobi R. Tip Recycling for Atomic Force Microscopy-Based Tip-Enhanced Raman Spectroscopy. APPLIED SPECTROSCOPY 2020; 74:1358-1364. [PMID: 32166961 DOI: 10.1177/0003702820916234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) is a powerful tool for the characterization of surfaces and two-dimensional materials, delivering both topographical and chemical information with nanometer-scale spatial resolution. Atomic force microscopy (AFM)-TERS combines AFM with a Raman spectrometer and is a very versatile technique, capable of working in vacuum, air, and liquid, and on a variety of different samples. A metalized AFM tip is necessary in order to take advantage of the plasmonic enhancement. The most commonly used metal is Ag, thanks to its high plasmonic activity in the visible range. Unfortunately, though, the tip metallization process is still challenging and not fully reliable, yielding inconsistent enhancement factors even within the same batch of tips; as a consequence, many tips are usually prepared at once (for a single experiment), to ensure that at least one of them is sufficiently active. As the lifetime of an unprotected, Ag-coated plasmonic probe is only a few hours, the procedure is inefficient and results in a substantial waste of materials and money. In this work, we establish a cleaning routine to effectively re-use Ag-coated AFM-TERS probes, drastically reducing costs without compromising the quality of the experimental results.
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Affiliation(s)
- Giovanni Luca Bartolomeo
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Guillaume Goubert
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
| | - Renato Zenobi
- Department of Chemistry and Applied Biosciences, Swiss Federal Institute of Technology (ETH) Zurich, Zurich, Switzerland
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Mahapatra S, Li L, Schultz JF, Jiang N. Tip-enhanced Raman spectroscopy: Chemical analysis with nanoscale to angstrom scale resolution. J Chem Phys 2020; 153:010902. [DOI: 10.1063/5.0009766] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Sayantan Mahapatra
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Linfei Li
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Jeremy F. Schultz
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
| | - Nan Jiang
- Department of Chemistry, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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9
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Gao L, Zhao H, Li Y, Li T, Chen D, Liu B. Controllable Fabrication of Au-Coated AFM Probes via a Wet-Chemistry Procedure. NANOSCALE RESEARCH LETTERS 2018; 13:366. [PMID: 30456453 PMCID: PMC6242804 DOI: 10.1186/s11671-018-2789-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 11/06/2018] [Indexed: 06/09/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS), which offers a spatial resolution far beyond the limitations of the optical diffraction and detection sensitivity down to a single molecular level, has become one of the powerful techniques applied in current nanoscience and technology. However, the excellent performance of a TERS system is very much dependent on the quality of metallized probes used in TERS characterization. Thus, how to prepare higher-quality probes plays a vital role in the development and application of TERS technique. In this work, one simple wet-chemistry procedure was designed to fabricate atomic force microscopy-based TERS (AFM-TERS) probes. Through the controlled growth of a gold film on a commercial silicon AFM probe, TERS probes with different apex diameters were prepared successfully. A series of TERS results indicated that the probes with the apex size of 50~60 nm had the maximum TERS enhancement, and the Raman enhancement factor was in the range of 106 to 107. Compared with those prepared by other fabrication methods, our TERS probes fabricated by this wet-chemistry method have the virtues of good stability, high reproducibility, and strong enhancement effect.
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Affiliation(s)
- Lizhen Gao
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
| | - Huiling Zhao
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
| | - Yinli Li
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
| | - Tianfeng Li
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
| | - Dong Chen
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
| | - Bo Liu
- Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng, 475004 People’s Republic of China
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10
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Foti A, Barreca F, Fazio E, D’Andrea C, Matteini P, Maragò OM, Gucciardi PG. Low cost tips for tip-enhanced Raman spectroscopy fabricated by two-step electrochemical etching of 125 µm diameter gold wires. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:2718-2729. [PMID: 30416923 PMCID: PMC6204785 DOI: 10.3762/bjnano.9.254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/08/2018] [Indexed: 05/26/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) has become a well-applied technique for nanospectroscopy, allowing for single molecule sensitivity with sub-nanometer spatial resolution. The demand for efficient, reproducible and cost-effective probes for TERS is increasing. Here we report on a new electrochemical etching protocol to fabricate TERS tips starting from 125 µm diameter gold wires in a reproducible way. The process is reliable (50% of the tips have radius of curvature <35 nm, 66% <80 nm), fast (less than 2 min) and 2.5 times cheaper than the etching of standard 250 µm diameter wires. The TERS performance of the tips is tested on dyes, pigments and biomolecules and enhancement factors higher than 105 are observed. TERS mapping with a spatial resolution of 5 nm is demonstrated.
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Affiliation(s)
- Antonino Foti
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
| | - Francesco Barreca
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Enza Fazio
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Cristiano D’Andrea
- IFAC-CNR, Institute of Applied Physics “Nello Carrara”, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
| | - Paolo Matteini
- IFAC-CNR, Institute of Applied Physics “Nello Carrara”, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
| | - Onofrio Maria Maragò
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
| | - Pietro Giuseppe Gucciardi
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
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11
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Tip-enhanced Raman spectroscopy: principles, practice, and applications to nanospectroscopic imaging of 2D materials. Anal Bioanal Chem 2018; 411:37-61. [DOI: 10.1007/s00216-018-1392-0] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 09/18/2018] [Accepted: 09/19/2018] [Indexed: 10/28/2022]
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12
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Mohaček-Grošev V, Gebavi H, Bonifacio A, Sergo V, Daković M, Bajuk-Bogdanović D. Binding of p-mercaptobenzoic acid and adenine to gold-coated electroless etched silicon nanowires studied by surface-enhanced Raman scattering. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2018; 200:102-109. [PMID: 29677496 DOI: 10.1016/j.saa.2018.04.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 03/30/2018] [Accepted: 04/09/2018] [Indexed: 06/08/2023]
Abstract
Modern diagnostic tools ever aim to reduce the amount of analyte and the time needed for obtaining the result. Surface-enhanced Raman spectroscopy is a method that could satisfy both of these requirements, provided that for each analyte an adequate substrate is found. Here we demonstrate the ability of gold-sputtered silicon nanowires (SiNW) to bind p-mercaptobenzoic acid in 10-3, 10-4 and 10-5M and adenine in 30 and 100μM concentrations. Based on the normal mode analysis, presented here for the first time, the binding of p-mercaptobenzoic acid is deduced. The intensity enhancement of the 1106cm-1 band is explained by involvement of the CS stretching deformation, and the appearance of the broad 300cm-1 band attributed to SAu stretching mode. Adenine SERS spectra demonstrate the existence of the 7H tautomer since the strongest band observed is at 736cm-1. The adenine binding is likely to occur in several ways, because the number of observed bands in the 1200-1600cm-1 interval exceeds the number of observed bands in the normal Raman spectrum of the free molecule.
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Affiliation(s)
- Vlasta Mohaček-Grošev
- Centre of Excellence for Advanced Materials and Sensing Devices, Ruđer Bošković Institute, Bijenička cesta 54, 10002 Zagreb, Croatia.
| | - Hrvoje Gebavi
- Centre of Excellence for Advanced Materials and Sensing Devices, Ruđer Bošković Institute, Bijenička cesta 54, 10002 Zagreb, Croatia
| | | | - Valter Sergo
- University of Trieste, Via Valerio 6/A, Trieste, Italy
| | - Marko Daković
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 15-16, 11000 Belgrade, Serbia
| | - Danica Bajuk-Bogdanović
- Faculty of Physical Chemistry, University of Belgrade, Studentski trg 15-16, 11000 Belgrade, Serbia
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13
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Huang TX, Li CW, Yang LK, Zhu JF, Yao X, Liu C, Lin KQ, Zeng ZC, Wu SS, Wang X, Yang FZ, Ren B. Rational fabrication of silver-coated AFM TERS tips with a high enhancement and long lifetime. NANOSCALE 2018; 10:4398-4405. [PMID: 29451566 DOI: 10.1039/c7nr08186c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS), known as nanospectroscopy, has received increasing interest as it can provide nanometer spatial resolution and chemical fingerprint information of samples simultaneously. Since Ag tips are well accepted to show a higher TERS enhancement than that of gold tips, there is an urgent quest for Ag TERS tips with a high enhancement, long lifetime, and high reproducibility, especially for atomic force microscopy (AFM)-based TERS. Herein, we developed an electrodeposition method to fabricate Ag-coated AFM TERS tips in a highly controllable and reproducible way. We investigated the influence of the electrodeposition potential and time on the morphology and radius of the tip. The radii of Ag-coated AFM tips can be rationally controlled at a few to hundreds nanometers, which allows us to systematically study the dependence of the TERS enhancement on the tip radius. The Ag-coated AFM tips show the highest TERS enhancement under 632.8 nm laser excitation and a broad localized surface plasmon resonance (LSPR) response when coupled to a Au substrate. The tips exhibit a lifetime of 13 days, which is particularly important for applications that need a long measuring time.
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Affiliation(s)
- Teng-Xiang Huang
- Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
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14
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Lahiri A, Lu T, Behrens N, Borisenko N, Li G, Endres F. Hydrofluoric Acid-Free Electroless Deposition of Metals on Silicon in Ionic Liquids and Its Enhanced Performance in Lithium Storage. ACS APPLIED MATERIALS & INTERFACES 2017; 9:11350-11355. [PMID: 28332814 DOI: 10.1021/acsami.7b01404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Metal nanoparticles such as Au, Ag, Pt, and so forth have been deposited on silicon by electroless deposition in the presence of hydrofluoric acid (HF) for applications such as oxygen reduction reaction, surface-enhanced Raman spectroscopy, as well as for lithium ion batteries. Here, we show an HF-free process wherein metals such as Sb and Ag could be deposited onto electrodeposited silicon in ionic liquids. We further show that, compared to electrodeposited silicon, Sb-modified Si demonstrates a better performance for lithium storage. The present study opens a new paradigm for the electroless deposition technique in ionic liquids for developing and modifying functional materials.
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Affiliation(s)
- Abhishek Lahiri
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
| | - Tianqi Lu
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
| | - Niklas Behrens
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
| | - Natalia Borisenko
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
| | - Guozhu Li
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
| | - Frank Endres
- Institute of Electrochemistry, Clausthal University of Technology , Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld, Germany
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15
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Wang X, Huang SC, Huang TX, Su HS, Zhong JH, Zeng ZC, Li MH, Ren B. Tip-enhanced Raman spectroscopy for surfaces and interfaces. Chem Soc Rev 2017; 46:4020-4041. [DOI: 10.1039/c7cs00206h] [Citation(s) in RCA: 162] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
TERS offers the high spatial resolution to establish structure-function correlation for surfaces and interfaces.
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Affiliation(s)
- Xiang Wang
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Sheng-Chao Huang
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Teng-Xiang Huang
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Hai-Sheng Su
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Jin-Hui Zhong
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Zhi-Cong Zeng
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Mao-Hua Li
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
| | - Bin Ren
- Collaborative Innovation Center of Chemistry for Energy Materials
- State Key Laboratory of Physical Chemistry of Solid Surfaces, and The MOE Key Laboratory of Spectrochemical Analysis and Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
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16
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Tharmaraj V, Yang J. An oxidation layer for regulating galvanically grown silver nanoparticles on silicon crystal for highly sensitive surface-enhanced Raman scattering measurements. CrystEngComm 2016. [DOI: 10.1039/c6ce02212j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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17
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Langelüddecke L, Singh P, Deckert V. Exploring the Nanoscale: Fifteen Years of Tip-Enhanced Raman Spectroscopy. APPLIED SPECTROSCOPY 2015; 69:1357-71. [PMID: 26554759 DOI: 10.1366/15-08014] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Spectroscopic methods with high spatial resolution are essential to understand the physical and chemical properties of nanoscale materials including biological and chemical materials. Tip-enhanced Raman spectroscopy (TERS) is a combination of surface-enhanced Raman spectroscopy (SERS) and scanning probe microscopy (SPM), which can provide high-resolution topographic and spectral information simultaneously below the diffraction limit of light. Even examples of sub-nanometer resolution have been demonstrated. This review intends to give an introduction to TERS, focusing on its basic principle and the experimental setup, the strengths followed by recent applications, developments, and perspectives in this field.
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Affiliation(s)
- Lucas Langelüddecke
- Institute of Physical Chemistry and Abbe Center of Photonics, University of Jena, Helmholtzweg 4, D-07743 Jena, Germany
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18
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Yang LK, Huang TX, Zeng ZC, Li MH, Wang X, Yang FZ, Ren B. Rational fabrication of a gold-coated AFM TERS tip by pulsed electrodeposition. NANOSCALE 2015; 7:18225-18231. [PMID: 26482226 DOI: 10.1039/c5nr04263a] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Reproducible fabrication of sharp gold- or silver-coated tips has become the bottleneck issue in tip-enhanced Raman spectroscopy, especially for atomic force microscopy (AFM)-based TERS. Herein, we developed a novel method based on pulsed electrodeposition to coat a thin gold layer over atomic force microscopy (AFM) tips to produce plasmonic TERS tips with high reproducibility. We systematically investigated the influence of the deposition potential and step time on the surface roughness and sharpness. This method allows the rational control of the radii of gold-coated TERS tips from a few to hundreds of nanometers, which allows us to systematically study the dependence of the TERS enhancement on the radius of the gold-coated AFM tip. The maximum TERS enhancement was achieved for the tip radius in the range of 60-75 nm in the gap mode. The coated gold layer has a strong adhesion with the silicon tip surface, which is highly stable in water, showing the great potential for application in the aqueous environment.
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Affiliation(s)
- Li-Kun Yang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Teng-Xiang Huang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Zhi-Cong Zeng
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Mao-Hua Li
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Xiang Wang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Fang-Zu Yang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
| | - Bin Ren
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
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19
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Deckert V, Deckert-Gaudig T, Diegel M, Götz I, Langelüddecke L, Schneidewind H, Sharma G, Singh P, Singh P, Trautmann S, Zeisberger M, Zhang Z. Spatial resolution in Raman spectroscopy. Faraday Discuss 2015; 177:9-20. [PMID: 25826010 DOI: 10.1039/c5fd90014j] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This article is intended to set the scope of the meeting, in particular, the high spatial resolution section.
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Affiliation(s)
- Volker Deckert
- Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.
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20
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Huang TX, Huang SC, Li MH, Zeng ZC, Wang X, Ren B. Tip-enhanced Raman spectroscopy: tip-related issues. Anal Bioanal Chem 2015; 407:8177-95. [PMID: 26314483 DOI: 10.1007/s00216-015-8968-8] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Revised: 08/02/2015] [Accepted: 08/05/2015] [Indexed: 11/29/2022]
Abstract
After over 15 years of development, tip-enhanced Raman spectroscopy (TERS) is now facing a very important stage in its history. TERS offers high detection sensitivity down to single molecules and a high spatial resolution down to sub-nanometers, which make it an unprecedented nanoscale analytical technique offering molecular fingerprint information. The tip is the core element in TERS, as it is the only source through which to support the enhancement effect and provide the high spatial resolution. However, TERS suffers and will continue to suffer from the limited availability of TERS tips with a high enhancement, good stability, and high reproducibility. This review focuses on the tip-related issues in TERS. We first discuss the parameters that influence the enhancement and spatial resolution of TERS and the possibility to optimize the performance of a TERS system via an in-depth understanding of the enhancement mechanism. We then analyze the methods that have been developed for producing TERS tips, including vacuum-based deposition, electrochemical etching, electrodeposition, electroless deposition, and microfabrication, with discussion on the advantages and weaknesses of some important methods. We also tackle the issue of lifetime and protection protocols of TERS tips which are very important for the stability of a tip. Last, some fundamental problems and challenges are proposed, which should be addressed before this promising nanoscale characterization tool can exert its full potential. Graphical Abstract ᅟ.
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Affiliation(s)
- Teng-Xiang Huang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Sheng-Chao Huang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Mao-Hua Li
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Zhi-Cong Zeng
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China
| | - Xiang Wang
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
| | - Bin Ren
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Key Laboratory of Analytical Sciences, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
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21
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Betz JF, Yu WW, Cheng Y, White IM, Rubloff GW. Simple SERS substrates: powerful, portable, and full of potential. Phys Chem Chem Phys 2014; 16:2224-39. [PMID: 24366393 DOI: 10.1039/c3cp53560f] [Citation(s) in RCA: 117] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Surface enhanced Raman spectroscopy (SERS) is a powerful spectroscopic technique capable of detecting trace amounts of chemicals and identifying them based on their unique vibrational characteristics. While there are many complex methods for fabricating SERS substrates, there has been a recent shift towards the development of simple, low cost fabrication methods that can be performed in most labs or even in the field. The potential of SERS for widespread use will likely be realized only with development of cheaper, simpler methods. In this Perspective article we briefly review several of the more popular methods for SERS substrate fabrication, discuss the characteristics of simple SERS substrates, and examine several methods for producing simple SERS substrates. We highlight potential applications and future directions for simple SERS substrates, focusing on highly SERS active three-dimensional nanostructures fabricated by inkjet and screen printing and galvanic displacement for portable SERS analysis - an area that we believe has exciting potential for future research and commercialization.
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Affiliation(s)
- Jordan F Betz
- Fischell Department of Bioengineering, University of Maryland, College Park, MD, USA
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22
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Liou YCM, Chen JY, Yang J. Enhancement of Raman scattering for silver nanoparticles located on electrolessly roughened silicon. APPLIED SPECTROSCOPY 2014; 68:172-178. [PMID: 24480272 DOI: 10.1366/13-07162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
To study the effect of roughness of a supporting substrate to Raman enhancement, silver nanoparticles (AgNPs) were prepared on Si with different degrees of roughness. To roughen the surface of silicon, electroless displacement was used first to grow AgNPs on smooth Si. By chemically removing the resulting AgNPs, an electrolessly roughened Si surface can be exposed. A second electroless displacement then was performed to grow new AgNPs on the roughened Si crystal to form surface-enhanced Raman scattering substrates. Another approach, called the protecting method, also was proposed and demonstrated to structure AgNPs on surface-roughened Si. In this second method, electroless displacement also was used to grow AgNPs on the Si crystal. The resulting AgNPs then were protected by thio compounds to control removal of the outer layer of AgNPs, thereby exposing the underlying AgNPs located directly on the electroless roughened Si surface. Results indicate that the structure of AgNPs on roughened Si surfaces provides approximately two orders of magnitude higher enhancement than AgNPs on non-roughened Si, and the substrates prepared in this work are highly sensitive, with enhancement factors reaching 10(8).
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Affiliation(s)
- Yen-Chen Maggie Liou
- Department of Chemistry, National Chung-Hsing University, Taichung 402, Taiwan, Republic of China
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23
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Jiang X, Jiang Z, Xu T, Su S, Zhong Y, Peng F, Su Y, He Y. Surface-Enhanced Raman Scattering-Based Sensing In Vitro: Facile and Label-Free Detection of Apoptotic Cells at the Single-Cell Level. Anal Chem 2013; 85:2809-16. [DOI: 10.1021/ac303337b] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Xiangxu Jiang
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Ziyun Jiang
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Tingting Xu
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Shao Su
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Yiling Zhong
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Fei Peng
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Yuanyuan Su
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
| | - Yao He
- Institute of Functional Nano & Soft Materials (FUNSOM) and Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices, Soochow University, Suzhou 215123, China
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24
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Wang C, Fang J, Jin Y. SERS activity studies of Ag/Au bimetallic films prepared by galvanic replacement. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 96:820-824. [PMID: 22925909 DOI: 10.1016/j.saa.2012.07.090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Revised: 07/18/2012] [Accepted: 07/23/2012] [Indexed: 06/01/2023]
Abstract
Ag films on Si substrates were fabricated by immersion plating, which served as sacrificial materials for preparation of Ag/Au bimetallic films by galvanic replacement method. SEM images displayed that the sacrificial Ag films presenting island morphology experienced interesting structural evolution process during galvanic replacement reaction, and nano-scaled holes were formed in the resultant bimetallic films. SERS measurements using crystal violet as an analyte showed that SERS intensities of bimetallic films were enhanced significantly compared with that of pure Ag films and related mechanisms were discussed. Immersion plating experiment carried out on Ag films on PEN substrates fabricated by photoinduced reduction method further confirmed that galvanic replacement is an easy method to fabricate Ag/Au bimetallic and a potential approach to improve the SERS performance of Ag films.
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Affiliation(s)
- Chaonan Wang
- School of Science, Nantong University, Jiangsu 226007, PR China
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25
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Betz JF, Cheng Y, Rubloff GW. Direct SERS detection of contaminants in a complex mixture: rapid, single step screening for melamine in liquid infant formula. Analyst 2012; 137:826-8. [DOI: 10.1039/c2an15846a] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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26
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Detection of Nucleic Acid Bases by Surface Enhanced Raman Scattering Based on In Situ Photo-Reduced Silver Colloids. CHINESE JOURNAL OF ANALYTICAL CHEMISTRY 2011. [DOI: 10.1016/s1872-2040(10)60465-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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27
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Gutés A, Carraro C, Maboudian R. Ultrasmooth gold thin films by self-limiting galvanic displacement on silicon. ACS APPLIED MATERIALS & INTERFACES 2011; 3:1581-1584. [PMID: 21476558 DOI: 10.1021/am200144k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Galvanic displacement (GD), a type of electroless deposition, has been used to obtain ultrasmooth gold thin films on silicon <111>. The novel aspect of the method presented herein is the absence of fluoride ions in the liquid phase, and its principal advantage when compared to previous efforts is that the process is inherently self-limiting. The self-limiting factor is due to the fact that in the absence of fluorinated species, no silicon oxide is removed during the process. Thus, the maximum gold film thickness is achieved when elemental silicon is no longer available once the surface is oxidized completely during the galvanic displacement process. X-ray photoelectron spectroscopy has been used as a tool for thickness measurement, using the gold to silicon ratio as an analytical signal. Three gold plating solutions with different concentrations of KAuCl₄ (2, 0.2, and 0.02 mM) have been used to obtain information about the formation rate of the gold film. This XPS analysis demonstrates the formation of gold films to a maximum thickness of ∼3.5 Å. Atomic force microscopy is used to confirm surface smoothness, suggesting that the monolayer growth does not follow the Volmer-Weber growth mode, in contrast to the GD process from aqueous conditions with fluorinated species.
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Affiliation(s)
- Albert Gutés
- Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA
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