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- 实验方案
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Detection of metal-molecule-metal junction formation by surface enhanced Raman spectroscopy
摘要： Vibrational modes play a key role in characterizing metal-molecule-metal junctions, but their detection currently either requires single-molecule sensitivity or the generation of defect-free large-scale junctions. Here we demonstrate that surface-enhanced Raman scattering (SERS) on non-ideal surfaces can provide a significant amount of information despite many defects in the layer. We determine the vibrational signature of the molecular electronic junction for palladium ions complexed and reduced on 4-mercaptopyridine adsorbed on rough gold and gold nanoparticles using SERS and density functional theory (DFT). We show that these non-ideal surfaces can be used to probe kinetics of metal ion complexation and establish the success of electrochemical metallization. SERS on non-ideal surfaces is thus revealed as a useful tool to rapidly establish the key process parameters in making molecular electronic junctions before embarking on more detailed studies on single molecules or single crystal surfaces.
关键词： gold,4-mercaptopyridine,Metal-molecule-metal junctions,surface-enhanced Raman spectroscopy
更新于2025-09-23 15:22:29
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Dual-wavelength Raman fusion spectroscopy
摘要： Spatially compressed dual-wavelength Raman spectroscopy allows recording the full Raman spectrum using a detection system with limited spectral range. The common approach is to record the spectra with the two excitation lasers consecutively and then concatenate the full spectrum. However, with this approach quantitative analysis for process monitoring is not possible as the investigated object may change between the two acquisitions. In this Note, spectral fusion is proposed as a concept to overcome this problem. The sample is illuminated by the two lasers simultaneously hence leading to an on-chip fusion of the different parts of the Raman spectrum. It is shown that the resulting data are suitable for quantitative evaluation using univariate and multivariate methods. Dual-wavelength Raman fusion spectroscopy offers new opportunities for building highly compact devices for analytical chemistry.
关键词： Raman spectroscopy,principal component analysis,data processing
更新于2025-09-23 15:22:29
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Reduced Graphene Oxide-Nanostructured Silicon Photosensors With High Photoresponsivity at Room Temperature
摘要： We have created nanostructured Si (~3 nm) with a direct band gap of 1.37 eV on electrically conducting reduced graphene oxide (rGO) for a highly efficient photosensor. This robust photosensor is fabricated using a non-equilibrium processing route, where nanosecond excimer laser pulses melt the alternating layers of Si and amorphous carbon to form micropillars and nanoreceptors of Si on rGO layers. The incident white light generates free carriers in the Si microstructures and nanoreceptors which are ballistically transported (via rGO layers) to the external circuit under the application of a voltage bias. The responsivity of rGO-Si devices to light (resistance vs time) and I-V measurements indicate an exponential drop in resistance with the incidence of white light and non-rectifying nature, respectively. Photoresponsivity of the rGO-Si devices is calculated to be 3.55 A/W at room temperature, which is significantly larger than the previously fabricated graphene-based Ohmic photosensors. Temperature-dependent resistance measurements of rGO-Si structures follow Efros-Shklovoskii variable range hopping (ES-VRH) electrical conduction in the low-temperature region (<100 K) and Arrhenius conduction in the high-temperature region (>100 K). In rGO, the localization length, hopping energy, and activation energy are calculated to be 17.58 μm, 3.15 meV, and 1.67 meV, respectively. The 2D nature of highly reduced and less defective rGO also render an interesting negative magnetoresistance (~2.5 %) at 5 K, thereby indicating potential implications of rGO-Si in opto-spintronics. The large-area integration of rGO-Si structures with sapphire employing nanosecond pulsed laser annealing and its exciting photosensing properties will open a new frontier for further extensive research in these functionalized 2D materials.
关键词： Pulsed laser annealing,Raman spectroscopy,Variable range hopping,Nanostructures,Reduced graphene oxide
更新于2025-09-23 15:22:29
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A Label-free Platform for Identification of Exosomes from Different Sources
摘要： Exosomes contain cell- and cell-state-specific cargos of proteins, lipids, and nucleic acids and play significant roles in cell signaling and cell–cell communication. Current research into exosome-based biomarkers has relied largely on analyzing candidate biomarkers, i.e., specific proteins or nucleic acids. However, this approach may miss important biomarkers that are yet to be identified. Alternative approaches are to analyze the entire exosome system, either by “omics” methods or by techniques that provide “fingerprints” of the system without identifying each individual biomolecule component. Here, we describe a platform of the latter type, which is based on surface-enhanced Raman spectroscopy (SERS) in combination with multivariate analysis, and demonstrate the utility of this platform for analyzing exosomes derived from different biological sources. First, we examined whether this analysis could use exosomes isolated from fetal bovine serum using a simple, commercially available isolation kit or necessitates the higher purity achieved by the “gold standard” ultracentrifugation/filtration procedure. Our data demonstrate that the latter method is required for this type of analysis. Having established this requirement, we rigorously analyzed the Raman spectral signature of individual exosomes using a unique, hybrid SERS substrate made of a graphene-covered Au surface containing quasi-periodic array of pyramids. To examine the source of the Raman signal, we used Raman mapping of low and high spatial resolution combined with morphological identification of exosomes by scanning electron microscopy. Both approaches suggested that the spectra were collected from single exosomes. Finally, we demonstrate for the first time that our platform can distinguish among exosomes from different biological sources based on their Raman signature, a promising approach for developing exosome-based fingerprinting. Our study serves as a solid technological foundation for future exploration of the roles of exosomes in various biological processes and their use as biomarkers for disease diagnosis and treatment monitoring.
关键词： surface-enhanced Raman spectroscopy,graphene,biomarker,exosome,principal component analysis
更新于2025-09-23 15:22:29
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Raman spectroscopic analysis of testicular lamina propria predicts spermatogenesis in a mouse infertility model
摘要： The status of the testicular lamina propria (LP) is associated with spermatogenesis. The aim of this study was to determine whether Raman spectroscopy (RS) could detect material components within the LP and predict spermatogenesis. Twenty adult male mice were divided into a busulfan-treated group (n ? 16 mice receiving a single injection of 50 mg kg(cid:2)1, i.p., busulfan) and a control group (n ? 4 mice receiving an equivalent volume of 0.9% saline solution injected i.p.). Mice were killed 2, 4, 6 and 8 weeks after injection of busulfan or saline solution (n ? 1 control and 4 busulfan-treated mice at each time point). The testicular tubules were assessed by RS and compared with histopathological observations. Control tubules had raw spectral intensities below 2000 arbitrary units, whereas busulfan tubules had strengthened intensities that peaked at Week 4 (absent spermatogenesis) and returned to normal levels at Week 8 (restored spermatogenesis). The change in the LP revealed by RS occurred before the change in spermatogenesis detected by histopathology. Correspondingly, the sensitivity/specificity of RS for distinguishing busulfan-treated and control tubules at 2, 4, 6 and 8 weeks were 65.00%/70.00%, 95.00%/100.00%, 40.00%/100.00% and 25.00%/95.00% respectively. Collectively, RS could be used to evaluate the status of the LP and as a complement to histopathological evaluation to predict tubules with the potential to develop spermatogenesis for infertile patients.
关键词： spermatogenesis,busulfan,mouse infertility model,testicular lamina propria,Raman spectroscopy
更新于2025-09-23 15:22:29
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Probing Electrolyte Solvents at Solid/Liquid Interface Using Gap-Mode Surface-Enhanced Raman Spectroscopy
摘要： Understanding the aprotic solution structures at the immediate vicinity of solid/liquid interface (SLI) is critically important for next generation lithium ion battery development. Yet, it is still challenging to investigate the carbonate chemical profiles close to the diffuse layer (about 10 nm) of the electrical double layer at SLI due to the lack of a ultrahigh surface sensitive tool. In this work, we demonstrate the structures of commonly used carbonate solvents (ethylene carbonate (EC) and diethyl carbonate (DEC)) and a carbonate additive (fluoroethylene carbonate (FEC)) in a commercial Li-ion battery electrolyte can be determined at ～17 nm above the electrode surface. This is only enabled by a nanogap surface-enhanced Raman spectroscopy (SERS) technique based on a monolayer gold nanoparticle (Au NP) ensemble. The SERS enhancement factor (EF) of those carbonates was found to depend on the molecular polarizability, with the maximum EF at ～105 found for EC and FEC. Despite their alike chemical structures, this monolayer Au NP SERS substrate is fully capable of discrimiating the different Raman finger prints of EC and FEC. Compared to EC, several vibration modes in FEC, such as C-C skeletal deformation, ring breathing band and C=O stretching band, shift to higher frequencies because of the displacement of a hydrogen atom by a much heavier fluorine atom in a methylene bridge. This counterintuitive observation against the commonly used “ball and spring” model in vibrational spectroscopy is mostly due to the increased bond strength in the FEC ring versus that of EC. A second order empirical polynomial best describes the correlation between the SERS band integration of EC or DEC molar concentration. Our findings open up new opportunities for in-depth understanding of the electrolyte molecular vibrational behaviors at direct solid/liquid interface and developing advanced electrolytes for next generation lithium-ion batteries.
关键词： carbonate solvents,electrolyte,solid/liquid interface,lithium-ion battery,surface-enhanced Raman spectroscopy
更新于2025-09-23 15:22:29
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The potential of biobanked liquid based cytology samples for cervical cancer screening using Raman spectroscopy.
摘要： Patient samples are unique and often irreplaceable. This allows biobanks to be a valuable source of material. The aim of this study was to assess the ability of Raman spectroscopy to screen for histologically confirmed cases of Cervical Intraepithelial neoplasia (CIN) using biobanked liquid based cytology (LBC) samples. Two temperatures for long term storage were assessed; 80oC and -25oC. The utility of Raman spectroscopy for the detection of CIN was compared for fresh LBC samples and biobanked LBC samples. Two groups of samples were used for the study with one group associated with disease (CIN3) and the other associated with no disease (cytology negative). The data indicates that samples stored at -80oC are not suitable for assessment by Raman spectroscopy due to a lack of cellular material and the presence of cellular debris. However, the technology can be applied to fresh LBC samples and those stored at -25oC and is, moreover, effective in the discrimination of negative samples from those where CIN 3 has been confirmed. Pooled fresh and biobanked samples are also amenable to the technology and achieve a similar sensitivity and specificity for CIN 3. This study demonstrates that cervical cytology samples stored within biobanks at temperatures that preclude cell lysis can act as a useful resource for Raman spectroscopy and will facilitate research and translational studies in this area.
关键词： cervical pre-cancer,cytology,ThinPrep,Raman spectroscopy,cervical cancer,biobank
更新于2025-09-23 15:22:29
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Distance-Resolving Raman Radar Based on a Time-Correlated CMOS Single-Photon Avalanche Diode Line Sensor
摘要： Remote Raman spectroscopy is widely used to detect minerals, explosives and air pollution, for example. One of its main problems, however, is background radiation that is caused by ambient light and sample fluorescence. We present here, to the best of our knowledge, the first time a distance-resolving Raman radar device that is based on an adjustable, time-correlated complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode line sensor which can measure the location of the target sample simultaneously with the normal stand-off spectrometer operation and suppress the background radiation dramatically by means of sub-nanosecond time gating. A distance resolution of 3.75 cm could be verified simultaneously during normal spectrometer operation and Raman spectra of titanium dioxide were distinguished by this system at distances of 250 cm and 100 cm with illumination intensities of the background of 250 lux and 7600 lux, respectively. In addition, the major Raman peaks of olive oil, which has a fluorescence-to-Raman signal ratio of 33 and a fluorescence lifetime of 2.5 ns, were distinguished at a distance of 30 cm with a 250 lux background illumination intensity. We believe that this kind of time-correlated CMOS single-photon avalanche diode sensor could pave the way for new compact distance-resolving Raman radars for application where distance information within a range of several metres is needed at the same time as a Raman spectrum.
关键词： time-correlated single photon counting (TCSPC),remote Raman spectroscopy,CMOS single-photon avalanche diode (SPAD),time interval measurement,distance-resolving Raman radar,stand-off Raman spectrometer
更新于2025-09-23 15:21:21
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In situ high-pressure spectroscopic studies using moissanite (4H-SiC) anvils
摘要： We examined the Raman scattering and IR absorption spectroscopy of 4H-SiC and its performance as an anvil material for high-pressure UV-visible absorption spectroscopic measurements. The first- and second-order Raman peaks of 4H-SiC and diamond do not coincide. 4H-SiC does not have obvious signals from 2330-5000 cm-1, suggesting that 4H-SiC anvils are beneficial for high-pressure studies of samples whose Raman signals locate in the region of diamond. Above 1800 cm-1, the transmitted signal of 4H-SiC in the IR absorption spectra, measured through 4.6 mm thickness is much higher than that of type IIa diamond. An in situ high-pressure UV-visible absorption spectroscopy study on CdI2 was carried out up to 28.0 GPa using 4H-SiC anvil cells (4H-SAC) with a 400 μm culet and the acquired band gap narrowed with increasing pressure. These results show that 4H-SiC has an excellent performance in high-pressure spectroscopic studies.
关键词： IR absorption spectroscopy,high-pressure,UV-visible absorption spectroscopy,Raman spectroscopy,4H-SiC
更新于2025-09-23 15:21:21
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[ACS Symposium Series] Raman Spectroscopy in the Undergraduate Curriculum Volume 1305 || Implementation of Raman Spectroscopy in an Undergraduate Forensic Chemistry Course
摘要： Raman spectroscopy has emerged as a valuable instrumental tool to supplement spectroscopic approaches, such as infrared spectroscopy for analyzing forensic samples including drugs, fibers, textiles, soil components, inks, pigments, paints, and body fluids, both in the field and at crime laboratories. As a result, Raman spectroscopy has been incorporated into undergraduate forensic chemistry courses. Using a Rigaku Progeny X2 Raman spectrometer, students recorded Raman spectra of organic and inorganic materials including drugs, adulterants, and coordination complexes. Students searched for matches using a chemical library and assigned peaks attributable to the chemical structures using a correlation table. They observed conditions in which Raman spectroscopy recorded bands not observed with the infrared spectrometer, reflecting the complementarity of the two techniques. An advantage of Raman spectroscopy for forensic analysis compared to infrared spectroscopy is that dangerous samples can be analyzed through containers and aqueous solutions can be analyzed without interference from water.
关键词： Raman spectroscopy,undergraduate education,infrared spectroscopy,forensic chemistry,forensic samples
更新于2025-09-23 15:21:21