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A single platform, integrated by a laser-induced breakdown spectroscopy detector and a Raman spectroscopy sensor, has been designed to remotely (5 m) and simultaneously register the elemental and molecular signatures of rocks under Martian surface conditions. From this information, new data fusion architecture at decisions level is proposed for the correct categorization of the rocks. The approach is based on a decision-making process from the sequential checking of the spectral features representing the cationic and anionic counterparts of the specimen. The scrutiny of the LIBS response by using a moving-window algorithm informs on the diversity of the elemental constituents. The output rate of emission lines allows projecting in a loop the elements as the cationic counterpart of the rock. In parallel, the Raman response of the unknown is compared with all the molecular counterparts of the hypothesized cation that are stored in a spectral library. The largest similarity rate unveils the final identity of the unknown. The identification capabilities of the architecture have been underscored through blind tests of 10 natural rocks with different origins. The great majority of forecasts have matched with the real identities of the inspected targets. The strength of this platform to simultaneously acquire the multielemental and the molecular information from a specimen by using the same laser events greatly enhances the "on-surface" missions for the surveillance of mineralogy. [ABSTRACT FROM AUTHOR]

We present a high-throughput screening Raman spectroscopy (HTS-RS) platform for a rapid and label-free macromolecular fingerprinting of tens of thousands eukaryotic cells. The newly proposed label-free HTS-RS platform combines automated imaging microscopy with Raman spectroscopy to enable a rapid label-free screening of cells and can be applied to a large number of biomedical and clinical applications. The potential of the new approach is illustrated by two applications. (1) HTS-RS-based differential white blood cell count. A classification model was trained using Raman spectra of 52 218 lymphocytes, 48 220 neutrophils, and 7 294 monocytes from four volunteers. The model was applied to determine a WBC differential for two volunteers and three patients, producing comparable results between HTS-RS and machine counting. (2) HTS-RS-based identification of circulating tumor cells (CTCs) in 1:1, 1:9, and 1:99 mixtures of Panc1 cells and leukocytes yielded ratios of 55:45, 10:90, and 3:97, respectively. Because the newly developed HTS-RS platform can be transferred to many existing Raman devices in all laboratories, the proposed implementation will lead to a significant expansion of Raman spectroscopy as a standard tool in biomedical cell research and clinical diagnostics. [ABSTRACT FROM AUTHOR]

Electrochemical deposition of aromatic organic molecules by reduction of diazonium reagents enables formation of molecular layers with sufficient integrity for use in molecular electronic junctions of interest to microelectronics. Characterization of organic films with thicknesses in the 1-10 nm range is difficult with Raman spectroscopy, since most molecular structures of electronic interest have Raman cross sections which are too small to observe as either thin films on solid electrodes or within intact molecular junctions. Layer formation on a 10 nm thick Ag island film on a flat carbon surface (eC/Ag) permitted acquisition of structural information using surface enhanced Raman spectroscopy (SERS), in many cases for molecules with weak Raman scattering. Raman spectra obtained on eC/Ag surfaces were indistinguishable from those on carbon without Ag present, and the spectra of oligomeric molecular layers were completely consistent with those of the monomers. Layer growth was predominantly linear for cases where such growth was sterically allowed, and linear growth correlated strongly with the line width and splitting of the C?C phenyl ring stretches. Molecular bilayers made by successive reduction of different diazonium reagents were also observable and will be valuable for applications of 1-20 nm organic films in molecular electronics. [ABSTRACT FROM AUTHOR]

Polarization-resolved Raman spectroscopy provides much more information than its conventional counterpart. However, it usually either requires a complicated setup with two spectrographs and detectors or two measurements must be performed sequentially. This study presents a simple and straightforward approach to recording both polarization components simultaneously with a single spectrograph and detector. The vertically and a horizontally polarized laser beam exiting a Wollaston prism are focused into the sample with a small spatial separation. The scattered light from both beams is imaged onto the slit of an imaging spectrograph as two spatially separated signals, i.e., the polarized and the depolarized Raman signal. Eventually, both spectra are acquired on a single CCD chip simultaneously. Experimental data of ethanol and dimethyl sulfoxide are shown as proof-of-concept. The new method has a number of advantages, for example, laser intensity fluctuations and the polarization dependence of the diffraction grating do not play a role. The proposed approach will be useful for an improved structural analysis and it will be the enabling technology for temporally resolved enantioselective Raman (esR) spectroscopy. [ABSTRACT FROM AUTHOR]

This paper demonstrates the direct sensing of glucose at physiologically relevant concentrations with surface-enhanced Raman spectroscopy (SERS) on gold film-over-nanosphere (AuFON) substrates functionalized with bisboronic acid receptors. The combination of selectivity in the bisboronic acid receptor and spectral resolution in the SERS data allow the sensors to resolve glucose in high backgrounds of fructose and, in combination with multivariate statistical analysis, detect glucose accurately in the 1–10 mM range. Computational modeling supports assignments of the normal modes and vibrational frequencies for the monoboronic acid base of our bisboronic acids, glucose and fructose. These results are promising for the use of bisboronic acids as receptors in SERS-based in vivo glucose monitoring sensors. [ABSTRACT FROM AUTHOR]

Product identification is a critical and required analysis for biotheraputics. In addition to regulatory requirements for identity testing on final drug products, in-process identity testing is implemented to reduce business risks associated with fill operations and can also be used as a tool against counterfeiting. Biotherapeutics, in particular monoclonal antibodies, represent a challenging cohort for identity determination because of their similarity in chemical structure. Traditional methods used for product identification can be time and labor intensive, creating a need for quick, inexpensive and reliable methods of drug identification. Here, driven by its molecular-specific and nonperturbative nature, we present Raman spectroscopy as an alternate analytical tool for identity testing. By exploiting subtle differences in vibrational modes of the biologics, we have developed partial least-squares-discriminant analysis derived decision algorithms that offer excellent differentiation capability using spontaneous Raman spectra as well as label-free plasmon-enhanced Raman spectra. Coupled with the robustness to spurious correlations due to its high information content, our results highlight the potential of Raman spectroscopy as a powerful method for rapid, on-site biotherapeutic product identification. [ABSTRACT FROM AUTHOR]

Orientational defects are molecular-scale point defects consisting of misaligned sterically trapped molecules. Such defects have been predicted in α-RDX using empirical force fields. These calculations indicate that their concentration should be higher than that of vacancies. In this study we confirm the stability of a family of four orientational defects in α-RDX using first-principles calculations and evaluate their formation energies and annealing barrier heights. The charge density distribution in the defective molecules is evaluated and it is shown that all four orientational defects exhibit some level of charge reduction at the midpoint of the N-N bond, which has been previously related to the sensitivity to initiation of the material. We also evaluate the vibrational spectrum of the crystal containing orientational defects and observe band splitting relative to the perfect crystal case. This may assist the experimental identification of such defects by Raman spectroscopy. [ABSTRACT FROM AUTHOR]

Controlling the packing structure and revealing the intermolecular interaction of self-assembled monolayers (SAMs) on solid surfaces are crucial for manipulating its properties. We utilized tip-enhanced Raman spectroscopy (TERS) to address the challenge in probing the subtle change of the intermolecular interaction during the assembly of a pyridine-terminated aromatic thiol on the single crystal Au (lll) surface that cannot produce enhanced Raman signal, together with electrochemical methods to study the charge transfer properties of SAM. We observed that the aromatic C = C bond stretching vibration can be a marker to monitor the strength of the intermolecular interaction of SAMs, because this Raman peak is very sensitive to the intermolecular π-π stacking. Our results indicate that the SAM experiences a surface restructuring after the formation of a densely packed monolayer. We propose that the intermolecular electrostatic repulsion governs the restructuring when the packing density is high. The correlated TERS and electrochemical studies also suggest that the intermolecular interaction may have some impact on the charge transfer properties of SAM. This study provides a molecular-level insight into understanding and exploiting the intermolecular interactions toward better control over the assembling process and tuning the electrical properties of aromatic thiols. [ABSTRACT FROM AUTHOR]

Here we describe enhanced Raman scattering at Au electrode 1 (E1)/Ag nanowire (NW)/4-aminothiophenol (4- ATP)/Au electrode 2 (E2) nanojunctions fabricated by combining self-assembly and metal electrodeposition at microgap electrodes (E1 and E2). In this method we assemble the 4-ATP on electrode E2 and electrodeposit Ag on the opposite electrode El of an Au interdigitated array (IDA) electrode device. The electrodeposited Ag grows in the form of NWs on E1 and makes nanoscale contact to E2 to form the junctions. The presence of the Ag NW leads to strong Raman scattering of the 4-ATP molecules within the nanojunction leading to estimated enhancement factors ranging from 103 to 106. Scanning electron microscopy (SEM) images provide insight into the morphology of the junctions. The magnitude of the Raman enhancement depends on the extent of contact between the Ag NW and the 4-ATP self-assembled monolayer (SAM). With this approach we could detect 4-ATP molecules diluted by a factor of 1000 with hexanethiol molecules within the junctions. Our approach is simple and fast with the potential to correlate electronic measurements of molecules with Raman spectroscopy data of the same molecules in a nanoscale junction for molecular electronics or chemiresistive sensing applications. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is a form of vibrational spectroscopy based on inelastic scattering of light. In resonance Raman spectroscopy, the wavelength of the incident light falls within an absorption band of a chromophore, and this overlap of excitation and absorption energy greatly enhances the Raman scattering efficiency of the absorbing species. The ability to probe vibrational spectra of select chromophores within a complex mixture of molecules makes resonance Raman spectroscopy an excellent tool for studies of biomolecules. In this Current Topic, we discuss the type of molecular insights obtained from steady-state and time-resolved resonance Raman studies of a prototypical photoactive protein, rhodopsin. We also review recent efforts in ultraviolet resonance Raman investigations of soluble and membrane-associated biomolecules, including integral membrane proteins and antimicrobial peptides. These examples illustrate that resonance Raman is a sensitive, selective, and practical method for studying the structures of biological molecules, and the molecular bonding, geometry, and environments of protein cofactors, the backbone, and side chains. [ABSTRACT FROM AUTHOR]

The first use of surface enhanced Raman spectroscopy (SERS) to detect trace organic and/or inorganic species in ambient atmospheric aerosol particles is presented. This new analytical method provides direct, spectroscopic detection of species present at attogram to femtogram levels in individual submicrometer atmospheric particles. An array of spectral features resulting from organic functional groups in secondary organic aerosol (SOA) material were observed in individual particles impacted on silver nanoparticle-coated substrates. The results demonstrate the complexity of organic and inorganic species in SOA formed by oxidation of biogenic volatile organic compounds (BVOCs) at the single particle level. While SOA composition is frequently assumed to be homogeneous between and within individual particles, substantial particle-to-particle variability in SOA composition and changes on scales <1 μm were observed. The observations obtained with this new method demonstrate the power of SERS to probe difficult to detect inter- and intraparticle variability in ambient SOA particles. [ABSTRACT FROM AUTHOR]

Immobilization of Cytochrome c oxidase(CcO) on electrodes makesvoltage-driven reduction of oxygen to water possible. Efficient catalyticturnover in CcO/electrode systems is, however, often observed at largeoverpotentials that cannot be rationalized by the redox propertiesof the enzyme itself. To understand the structural basis for thisobservation, CcO was electrostatically adsorbed on amino-functionalizedAg electrodes, and the redox transitions of heme aand a3were monitored via surface enhancedresonance Raman spectroscopy (SERRS) as a function of applied potential.Under completely anaerobic conditions, the reduction of heme a3could be seen at potentials close to thosemeasured in solution indicating an intact catalytic center. However,in the immobilized state, a new non-native heme species was observedthat exhibited a redox potential much more negative than measuredfor the native hemes. Analysis of the high and low frequency SERRspectra indicated that this new species is formed from heme aupon axial loss of one histidine ligand. It is concludedthat the formation of the non-native heme aspeciesalters the potential-dependent electron supply to the catalytic reactionand, thus, can have a impact on the applicability of this enzyme inbiofuel cells. [ABSTRACT FROM AUTHOR]

Saline aqueous solutions at elevatedpressures and temperaturesplay an important role in processes such as supercritical water oxidation(SCWO) and supercritical water gasification (SCWG), as well as innatural geochemical processes in Earth and planetary interiors. Somesolutions exhibit a negative temperature coefficient of solubilityat high temperatures, thereby leading to salt precipitation with increasingtemperature. Using modulated FT-IR Raman spectroscopy and classicalmolecular dynamics simulations (MD), we studied the solute speciationin solutions of 10 wt % Na2SO4, at conditionsclose to the saturation limit. Our experiments reveal that ion pairingand cluster formation are favored as solid saturation is approached,and ionic clusters form prior to the precipitation of solid sulfate.The proportion of such clusters increases as the phase boundary isapproached either by decreasing pressure or by increasing temperaturein the vicinity of the three-phase (vapor–liquid–solid)curve. [ABSTRACT FROM AUTHOR]

The dynamic properties of phospholipid (PL) membranes (phase state and phase transition) play crucial roles in biological systems. However, highly sensitive, direct analytical methods that shed light on the nature of lipids and their assemblies have not been developed to date. Here, we describe the analysis of PL-modified Au nanoparticles (Au@PL) using membrane surface-enhanced Raman spectroscopy (MSERS) and report the properties of the self-assembled PL membranes on the Au nanoparticle. The Raman intensity per PL concentration increased by 50-170 times with Au@PL, as compared to large unilamellar vesicles (LUVs) at the same PL concentration. The phase state and phase transition temperature of the PL membrane of Au@PL were investigated by analyzing the Raman peak ratio (R = I2882/I2930). The enhancement at 714 cm-1 (EF(714)) varied with the hydrocarbon chain length of the PLs and the assembled degree of Au@PLs. In calculation, the EF(714),assembled was estimated to be 111-142 when the distance between AuNPs was 7.0-7.5 nm, which was correlated to the speculative enhancement factor, suggesting that the assembly of the Au@PLs contributed to the MSERS. [ABSTRACT FROM AUTHOR]

A new, novel, rapid method to detect and direct readout of drugs in human urine has been developed using dynamic surface-enhanced Raman spectroscopy (D-SERS) with portable Raman spectrometer on gold nanorods (GNRs) and a classification algorithm called support vector machines (SVM). The high-performance GNRs can generate gigantic enhancement and the SERS signals obtained using D-SERS on it have high reproducibility. On the basis of this feature of DSERS, we have obtained SERS spectra of urine and urine containing methamphetamine (MAMP). SVM model was built using these data for fast identified and visual results. This general method was successfully applied to the detection of 3, 4-methylenedioxy methamphetamine (MDMA) in human urine. To verify the accuracy of the model, drug addicts' urine containing MAMP were detected and identified correctly and rapidly with accuracy more than 90%. The detection results were displayed direcdy without analysis of their SERS spectra manually. Compared with the conventional method in lab, the method only needs a 2 pL sample volume and takes no more than 2 min on the portable Raman spectrometer. It is anticipated that this method will enable rapid, convenient detection of drugs on site for the police. [ABSTRACT FROM AUTHOR]

Hair is one of the most common types of physical evidence found at a crime scene. Forensic examination may suggest a connection between a suspect and a crime scene or victim, or it may demonstrate an absence of such associations. Therefore, forensic analysis of hair evidence is invaluable to criminal investigations. Current hair forensic examinations are primarily based on a subjective microscopic comparison of hair found at the crime scene with a sample of suspect's hair. Since this is often inconclusive, the development of alternative and more-accurate hair analysis techniques is critical. In this study, we utilized surface-enhanced Raman spectroscopy (SERS) to demonstrate that artificial dyes can be directly detected on hair. This spectroscopic technique is capable of a confirmatory identification of analytes with single molecule resolution, requires minimal sample, and has the advantage of fluorescence quenching. Our study reveals that SERS can (1) identify whether hair was artificially dyed or not, (2) determine if a permanent or semipermanent colorants were used, and (3) distinguish the commercial brands that are utilized to dye hair. Such analysis is rapid, minimally destructive, and can be performed directly at the crime scene. This study provides a novel perspective of forensic investigations of hair evidence. [ABSTRACT FROM AUTHOR]

Although surface-enhanced Raman spectroscopy (SERS) has been featured by high sensitivity, additional signal enhancement is still necessary for trace amount of biomolecules detection. In this paper, a SERS amplified approach, featuring "ions-mediated cascade amplification (IMCA)", was proposed by utilizing the dissolved silver ions (Ag+) from silver nanoparticles (AgNPs). We found that using Ag+ as linkage agent can effectively control the gaps between neighboring 4-aminobenzenethiol (4-ABT) encoded gold nanoparticles (AuNPs@4-ABT) toform "hot spots" and thus produce SERS signal output, in which the SERS intensity was proportional to the concentration of Ag+. Inspired by this finding, the IMCA was utilized for ultrasensitive detection of single nucleotide polymorphism in human mitochondrial DNA (16189T → C). Combining with the DNA ligase reaction, each target DNA binding event could successfully cause one AgNP introduction. By detecting the dissolved Ag+ from AgNPs using IMCA, low to 3.0 × 10(-5) fm/μL targeted DNA can be detected, which corresponds to extractions from 200 nL cell suspension containing carcinoma pancreatic β-cell lines from diabetes patients. This IMCA approach is expected to be a universal strategy for ultrasensitive detection of analytes and supply valuable information for biomedical research and clinical early diagnosis. [ABSTRACT FROM AUTHOR]

Thesymmetric CC stretching frequency (νЯ) of conjugated polymers and oligomers is a sensitive spectroscopicreporter of molecular structure and material morphologies; however,thorough understanding of how structure affects this frequency islacking because computational investigations of this relationshiphave been undertaken with limited approaches. We present a comprehensivecomputational investigation of the structure-dependent Raman spectroscopyof oligothiophenes, oligofurans, and oligopyrroles in their groundelectronic states using density functional theory. We assessed howvarious functionals (BLYP, B3LYP, BHLYP, and CAM-B3LYP) impact predictionsof length-dependent trends in νЯ. The amountof Hartree–Fock exchange in a functional is critical for accuratelytreating π-delocalization and polarizability and hence the structure-dependentRaman behavior. BLYP and B3LYP fail to accurately predict trends inνЯwith oligomer length because they over-representdelocalization; in contrast, the range-corrected CAM-B3LYP functionalproduces the same trends observed experimentally for oligomers insolution and in the solid phase. Through comparisons with a simplemechanical model, we demonstrate that the length- and conformation-dependentspectroscopy of oligothiophenes results from a delicate balance betweendelocalization-induced softening of νЯandthe coupling of oscillators that increase νЯ. These findings are used to address how variations in inter- andintramolecular order impact the Raman spectroscopy of polythiophenes. [ABSTRACT FROM AUTHOR]

Four spinel ferrite compositions of the CuAlxFe2-xO4, x = 0.0, 0.2, 0.4, 0.6, system prepared by usual double-sintering ceramic route and quenched (rapid thermal cooling) from final sintering temperature (1373 K) to liquid nitrogen temperature (80 K) were investigated by employing X-ray powder diffractometry, 57Fe Mossbauer spectroscopy, and micro-Raman spectroscopy at 300 K. The Raman spectra collected in the wavenumber range of 100-1000 cm-1 were analyzed in a systematic manner and showed five predicted modes for the spinel structure and splitting of A1g Raman mode into two/three energy values, attributed to peaks belonging to each ion (Cu2+, Fe3+, and Al3+) in the tetrahedral positions. The suppression of lower-frequency peaks was explained on the basis of weakening in magnetic coupling and reduction in ferrimagnetic behavior as well as increase in stress induced by square bond formation on Al3+ substitution. The enhancement in intensity, random variation of line width, and blue shift for highest frequency peak corresponding to A1g mode were observed. The ferric ion (Fe3+) concentration for different compositions determined from Raman spectral analysis agrees well with that deduced by means of X-ray diffraction line-intensity calculations and Mossbauer spectral analysis. An attempt was made to determine elastic and thermodynamic properties from Raman spectral analysis and elastic constants from cation distribution. [ABSTRACT FROM AUTHOR]

Interesting properties of water with distinguishable hydrogen-bonding structure on interfacial phase or in confined environment have drawn wide attentions. However, these unique properties of water are only found within the interfacial phase and confined environment, thus, their applications are limited. In addition, quantitative evaluation on these unique properties associating with the enhancement of water's physical and chemical activities represents a notable challenge. Here we report a practicable production of free-standing liquid water at room temperature with weak hydrogen-bonded structure naming Au nanoparticles (NPs)-treated (AuNT) water via treating by plasmon-induced hot electron transfer occurred on resonantly illuminated gold NPs (AuNPs). Compared to well-known untreated bulk water (deionized water), the prepared AuNT water exhibits many distinct activities in generally physical and chemical reactions, such as high solubilities to NaCl and O2. Also, reducing interaction energy within water molecules provides lower overpotential and higher efficiency in electrolytic hydrogen production. In addition, these enhanced catalytic activities of AuNT water are tunable by mixing with deionized water. Also, most of these tunable activities are linearly proportional to its degree of nonhydrogen-bonded structure (DNHBS), which is derived from the O-H stretching in deconvoluted Raman spectrum. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is generally performed on planar surfaces, which can be difficult to prepare and may limit the interaction of the sensing surface with targets in large volume samples. We propose that nanocomposite materials can be configured that both include SERS probes and provide a high surface area-to-volume format, i.e., fibers. Thiol-yne nanocomposite films and fibers were fabricated using exposure to long-wave ultraviolet light after the inclusion of gold nanoparticles (AuNPs) functionalized with thiophenol. A SERS response was observed that was proportional to the aggregation of the AuNPs within the polymers and the amount of thiophenol present. Overall, this proof-of-concept fabrication of SERS active polymers indicated that thiol-yne nanocomposites may be useful as durable film or fiber SERS probes. Properties of the nanocomposites were evaluated using various techniques including UV-vis spectroscopy, μ-Raman spectroscopy, dynamic mechanical analysis, differential scanning calorimetry, therm ogravimetric analysis, and transmission electron microscopy. [ABSTRACT FROM AUTHOR]

This laboratory exercise introduces undergraduate chemistry majors to the spectroscopic and theoretical study of the polycyclic aromatic hydrocarbon (PAH), corannulene. Students explore the spectroscopic properties of corannulene using UV-vis and Raman vibrational spectroscopies. They compare their experimental results to simulated vibrational spectra and the molecular structure obtained from computational chemistry to other PAHs, including C60. The delocalized electron in corannulene is also conceptually explored using the particle in a disk model. This laboratory exercise allows students to explore multiple physical chemistry concepts in one, 3 h laboratory exercise centered around one theme. [ABSTRACT FROM AUTHOR]

Theeffect of adding TeO2into (100 – x)[0.5Ag2O – 0.1B2O3–0.4P2O5] – xTeO2,with 0–80 mol % TeO2glass, on the structuralchanges and electrical properties has been investigated. DSC and thermodilatomerywere used to study their thermal behavior, structure was studied byRaman spectroscopy, and electrical properties have been studied byimpedance spectroscopy over a wide temperature and frequency range.The introduction of TeO2as a third glass former to theglass network causes the structural transformation from TeO3(tp) to TeO4(tbp) which contributes to the changes inconductivity. The glasses with low TeO2content show onlya slow decrease in dc conductivity with addition of TeO2due to the increase of the number of nonbridging oxygens, whichincreases the mobility of Ag+ions. The steep decreasein conductivity for glasses containing more than 40 mol % TeO2is a result of decrease of the Ag2O content andstronger cross-linkage in glass network through the formation of moreTe–eqOax–Te bonds in TeO4tbp units. The glasses obey ac conductivity scaling with respectto temperature, implying that the dynamic process is not temperaturedependent. On the other hand, the scaling of the spectra for differentglass compositions showed the deviations from the Summerfield scalingbecause of the local structural disorder which occurs as a resultof the structural modifications in the tellurite glass network. [ABSTRACT FROM AUTHOR]

A term project was introduced in teaching advanced spectroscopy and notions of nanotechnology to chemistry students at the graduate level (M.Sc. and Ph.D.). This project could also be suited for an honor's thesis at the undergraduate level. Students were assigned a unique combination of nanoparticle synthesis (13 nm Au nanospheres, ~100 nm nanoraspberries or ~50 nm nanostars) and fluorescent/Raman-active ligand (HS-PEG-FITC, rhodamine 6G, 4-mercaptobenzoic acid, 4-nitrobenzenethiol, and phenanthroline). Characterization with transmission electron microscopy allowed the students to confirm the shape and size distribution of nanoparticles. The ligands immobilized on the surface of the nanoparticles were extensively characterized using a suite of optical techniques. UV-vis was used to observe the plasmonic bands of particles of varying shapes, and fluorescent spectroscopy was used to construct fluorescent pathways with the aid of Jablonski diagrams. The vibrational bands of the ligands were identified using IR and Raman spectroscopy. Performing surface-enhanced Raman spectroscopy (SERS) on the nanoparticle at different excitation wavelength (488, 633, and 785 nm) was used to understand the influence of the surface plasmon on SERS and fluorescence spectroscopies. Students were required to write a full scientific paper for the report of the term project. [ABSTRACT FROM AUTHOR]

Understanding cellular metabolism is a major challenge in current systems biology and has triggered extensive metabolomics research, which in most cases involves destructive analysis. However, the information obtainable only in a nondestructive manner will be required for accurately mapping the global structure of the organism's metabolic network at a given instant. Here we report that metabolic pathways can be explored in vivo by mixed stable isotope-labeled Raman microspectroscopy in conjunction with multivariate curve resolution analysis. As a model system, we studied ergosterol biosynthesis in single living fission yeast cells grown in mixtures of normal and 13C-labeled glucose as the sole carbon source. The multivariate spectral data analysis of space-resolved Raman spectra revealed the intrinsic spectra and relative abundances of all isotopomers of ergosterol whose carbon atoms in the 5,7-diene moiety of the sterol skeleton are either partly or fully substituted with 13C. Our approach is applicable to other metabolites and will earn a place in the toolbox of metabolomic analysis. [ABSTRACT FROM AUTHOR]

A combination of absorption, electron paramagnetic resonance (EPR), and resonance Raman (rR) spectroscopy has been used to study the interaction of heme-Aβ and apomyoglobin (apoMb). The absorption spectrum of oxidized heme bound Aβ, characterized by a split Soret band at 364 and 394 nm, shifts to 408 nm on incubation with apoMb, characteristic of Myoglobin (Mb). The ν4, ν3, and ν2 bands in the rR spectrum of heme-Aβ are observed at 1376, 1495, and 1570 cm-1, which shift to 1371, 1482, and 1563 cm-1, respectively on incubating with apoMb, implying formation of Mb. Similarly, heme transfer from reduced heme-Aβ to apoMb resulting in the formation of deoxyMb was also observed. Thus, spectroscopic data show that apoMb can sequester heme from heme-Aβ complexes both in oxidized and in reduced forms. Heme uptake by apoMb from native heme-Aβ(1-40) and Aβ(1-16) in both oxidized and reduced forms follow a biphasic reaction kinetics likely representing heme transfer from two dominating conformers of heme-Aβ in solution. The rate constants for the two steps involved in heme uptake by apoMb from heme-Aβ(1-40) are 11.5 × 104 M-1 s-1 and 7.5 × 10³ M-1 s-1 while from heme-Aβ(1-16) are 6.0 × 104 M-1 s-1 and 7.5 × 10³ M-1 s-1. The rate constants for heme uptake by apoMb from reduced heme-Aβ(1-40) are 3.7 × 104 M-1 s-1 and 6.8 × 10³ M-1 s-1 while for reduced heme-Aβ(1-16) are 2.0 × 104 M-1 s-1 and 6.0 × 10³ M-1 s-1. The heme uptake from heme-Aβ by apoMb leads to a dramatic reduction of PROS generation by the reduced heme-Aβ complexes. [ABSTRACT FROM AUTHOR]

Compoundsrich in nitrogen are attracting significant interestnot only because of their high energy content but also because theyare potentially more environmentally benign in comparison to conventionalenergetic materials. Given this interest, it is desirable to understandtheir molecular composition and structural variations with pressureto derive their stability and determine the conditions in which theytransform physically or chemically. In this study, we examine theroom-temperature isothermal compression behavior of bis-triaminoguanidiniumazotetrazolate (TAGzT) by in situ Raman spectroscopy to pressuresnear 17 GPa. We assign the characteristic vibrational bands and reportthe effects of pressure on band intensity, line width, and frequencyshift. Two prominent peaks near 1370 and 1470 cm–1arise from the C–N and NN symmetric stretches, respectively.Overall, the intensity of these bands and others diminishes with pressure,and their spectral linewidths increase monotonically upon compression.The vibrational frequency modes blue shift linearly upon compression,indicating a generalized stiffening of the bonds as the pressure increases.These results, together with micro Raman spectroscopic analyses ofthe recovered, decompressed samples, suggest that TAGzT does not undergoany phase transitions within this pressure range. We estimate andreport the C–N and NN intermolecular bond lengths undercompression. [ABSTRACT FROM AUTHOR]

This work demonstrates the development of near-infraredsurface-enhanced Raman spectroscopy (NIR-SERS) for the identificationof eosin Y, an important historical dye. NIR-SERS benefits from theabsence of some common sources of SERS signal loss including photobleachingand plasmonic heating, as well as an advantageous reduction in fluorescence,which is beneficial for art applications. This work also representsthe first rigorous comparison of the enhancement factors and the relativemerits of two plasmonic substrates utilized in art applications; namely,citrate-reduced silver colloids and metal film over nanosphere (FON)substrates. Experimental spectra are correlated in detail with theoreticalabsorption and Raman spectra calculated using time-dependent densityfunctional theory (TDDFT) in order to elucidate molecular structuralinformation and avoid relying on pigment spectral libraries for dyeidentification. [ABSTRACT FROM AUTHOR]

Tight control of charge transport from a visible light sensitizer to a metal oxide nanoparticle catalyst for water oxidation is a critical requirement for developing efficient artificial photosynthetic systems. By utilizing covalently anchored molecular wires for hole transport from sensitizer to the oxide surface, the challenge of high rate and unidirectionality of the charge flow can be addressed. Functionalized hole conducting molecular wires of type p-oligo(phenylenevinylene) (3 aryl units, abbreviated PV3) with various anchoring groups for the covalent attachment to Co3O4 catalyst nanoparticles were synthesized and two alternative methods for attachment to the oxide nanoparticle surface introduced. Covalent anchoring of intact PV3 molecules on Co3O4 nanoparticles (and on SiO2 nanoparticles for control purposes) was established by FT-Raman, FT-IR, and optical spectroscopy including observation, in some cases, of the vibrational signature of the anchored functionality. Direct monitoring of the kinetics of hole transfer from a visible light sensitizer in aqueous solution ([Ru(bpy)3]2+ (and derivatives) light absorber, [Co(NH3)5Cl]2+ acceptor) to wire molecules on inert SiO2(12 nm) particles by nanosecond laser absorption spectroscopy revealed efficient, encounter controlled rates. For wire molecules anchored on Co3O4 nanoparticles, the recovery of the reduced sensitizer at 470 nm indicated similarly efficient hole transfer to the attached PV3, yet no transient hole signal was detected at 600 nm. This implies hole injection from the anchored wire molecule into the Co3O4 particle within 1 μs or shorter, indicating efficient charge transport from the visible light sensitizer to the oxide catalyst particle. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is able to probe disorder in graphenethroughdefect-activated peaks. It is of great interest to link these featuresto the nature of disorder. Here we present a detailed analysis ofthe Raman spectra of graphene containing different type of defects.We found that the intensity ratio of the D and D′ peak is maximum(∼13) for sp3-defects, it decreases for vacancy-likedefects (∼7), and it reaches a minimum for boundaries in graphite(∼3.5). This makes Raman Spectroscopy a powerful tool to fullycharacterize graphene. [ABSTRACT FROM AUTHOR]

Total internal reflection (TIR) Raman and reflectivity spectra were collected for nonresonant analytes as a function of incident angle at sapphire or sapphire/smooth 50 rim gold interfaces using 785 nm excitation. For both interfaces, the Raman signal as a function of incident angle is well-modeled by the calculated interfacial mean square electric field (MSEF) relative to the incident field times the thickness of the layer being probed in the Ransan measurement (Das). The Raman scatter was reproducibly enhanced at the interface containing a gold film relative to the sapphire interface by a factor of 4.3-4.6 for aqueous pyridine or 2.2-3.7 for neat nitrobenzene, depending on the analyzed vibrational mode. The mechanism for the increased Raman signal is the enhanced MSEF at incident angles where propagating surface plasmons are excited in the metal film. The background from the TIR prism was reduced by 89-95% with the addition of the gold film, and the percent relative uncertainty in peak area was reduced from 15 to 1.7% for the 1347 cm-1 mode of nitrobenzene. Single monolayers of benzenethiol (S/N = 6.8) and 4-mercaptopyridine (S/N = 16.5) on gold films were measured by TW Raman spectroscopy with 785 rim excitation (210 mW) without resonant enhancement in 1 mm. [ABSTRACT FROM AUTHOR]

The ability to unequivocally identify a gunshot residue (GSR) when a firearm is discharged is a very important and crucial part of crime scene investigation. To date, the great majority of the analyses have focused on the inorganic components of GSR, but the introduction of "lead-free" or "nontoxic" ammunitions makes it difficult to prevent false negatives. This study introduces a fast methodology for the organic analysis of GSR using Raman spectroscopy. Six different types of ammunition were fired at short distances into cloth targets, and the Raman spectra produced by the GSR were measured and compared with the spectra from the unfired gunpowder ammunition. The GSR spectrum shows high similarity to the spectrum of the unfired ammunition, allowing the GSR to be traced to the ammunition used. Additionally, other substances that might be found on the victim's, shooter's, or suspect's clothes and might be confused with GSR, such as sand, dried blood, or black ink from a common ballpoint pen, were analyzed to test the screening capability of the Raman technique. The results obtained evidenced that Raman spectroscopy is a useful screening tool when fast analysis is desired and that little sample preparation is required for the analysis of GSR evidence. [ABSTRACT FROM AUTHOR]

We introduce a new design approach for surface-enhancedRaman spectroscopy(SERS) substrates that is based on molding the optical powerflow througha sequence of coupled nanoscale optical vortices “pinned”to rationally designed plasmonic nanostructures, referred to as VortexNanogear Transmissions (VNTs). We fabricated VNTs composed of Au nanodiscsby electron beam lithography on quartz substrates and characterizedtheir near- and far-field responses through combination of computationalelectromagnetism, and elastic and inelastic scattering spectroscopy.Pronounced dips in the far-field scattering spectra of VNTs provideexperimental evidence for an efficient light trapping and circulationwithin the nanostructures. Furthermore, we demonstrate that VNT integrationinto periodic arrays of Au nanoparticles facilitates the generationof high E-field enhancements in the VNTs at multiple defined wavelengths.We show that spectrum shaping in nested VNT structures is achievedthrough an electromagnetic feed-mechanism driven by the coherent multiplescattering in the plasmonic arrays and that this process can be rationallycontrolled by tuning the array period. The ability to generate highE-field enhancements at predefined locations and frequencies makesnested VNTs interesting substrates for challenging SERS applications. [ABSTRACT FROM AUTHOR]

The nature of the lowest energy optical transition for the complexes (η6-naphthalene)Cr(CO)3 and (η6-phenanthrene)Cr(CO)3 in the solid state has been investigated by Raman spectroscopy using a range of different excitation wavelengths progressively approaching the resonant condition. Examination of the resonantly enhanced Raman modes confirms that the first absorption is attributed predominantly to a metal-to-arene charge transfer transition for both complexes. A notable difference in the photochemistry of the two complexes was observed. In the case of the phenanthrene complex, population of the lowest energy excited state leads to a photochemical process which resulted in the loss of the arene ligand and formation of Cr(CO)6. [ABSTRACT FROM AUTHOR]

We present a systematic Raman study over a range of excitation energies of arc discharge single-walled carbon nanotubes (SWCNTs) covalently functionalized according to two processes, esterification and reductive alkylation. The SWCNTs are characterized by resonance Raman spectroscopy at each step of the functionalization process, showing changes in radial breathing mode frequencies and transition energies for both semiconducting and metallic tubes. Particular attention is given to a family of tubes clearly identified in the Kataura plot for which we continuously tune the excitation energy from 704 to 752 nm. This allows us to quantify the energy shift occurring in the spacing of the van Hove singularities. We demonstrate that, independently of the functionalization technique, the type of chain covalently bound to the tubes plays an important role, notably when oxygen atoms lie close to the tubes, inducing a larger shift in transition energy as compared to that of other carbonaceous chains. The study shows the complexity of interpreting Raman data and suggests many interpretations in the literature may need to be revisited. [ABSTRACT FROM AUTHOR]

An experimental and theoretical study of the tautomeric composition of adenine (Ade) in water using Raman spectroscopy is reported. Experimental resonance Raman spectra of adenine at excitation wavelengths of 200, 218, and 266 nm were compared with quantum-mechanical calculations of N9H- and N7H-adenine tautomers and their cations. Both theoretical and experimental studies of nonresonance Raman spectra (457 nm excitation) of adenine were also performed for comparison. A satisfactory agreement of the calculated results with the experimental data was obtained. The Raman spectra are interpreted, and the basic regularities of the Raman intensity distribution are explained. On the basis of the analysis performed, the tautomeric composition of adenine in water is revealed. It is shown that the Ade-N9,N1H+ cation is the predominant form and that some neutral forms of Ade-N9H and Ade-N7H tautomers exist in water at pH 3. [ABSTRACT FROM AUTHOR]

An unprecedented control of the spectral response of plasmonic nanoantennas has recently been achieved by designing structures that exhibit Fano resonances. This new insight is paving the way for a variety of applications, such as biochemical sensing and surface-enhanced Raman spectroscopy. Here we use scattering-type near-field optical microscopy to map the spatial field distribution of Fano modes in infrared plasmonic systems. We observe in real space the interference of narrow (dark) and broad (bright) plasmonic resonances, yielding intensity and phase togglingbetween different portions of the plasmonic metamolecules when either their geometric sizes or the illumination wavelength is varied. [ABSTRACT FROM AUTHOR]

Sulfuryl diazide, O2S(N3)2, previously described as an "exceedingly explosive" compound, has been isolated and characterized by IR (Ar matrix, gas) and Raman (solid) spectroscopy, and its structure has been determined by X-ray crystallography. It has a melting point of -15 ¼C and can be handled in small quantities in gas, liquid, and solid states. Vibrational spectroscopic studies suggest the presence of only one conformer in both gas and solid states, and the X-ray crystallography revealed an anti conformation of the two azido groups with respect to the NSN plane. Calculations predict the anti (C2) conformer to be 6.6 kJ mol-1 lower in energy than the syn (Cs) one at the CBS-QB3 level of theory. The related chlorosulfuryl azide, ClSO2N3, has also been prepared and characterized by IR and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

First examples of the coordination chemistry of the PAs3S3 cage were obtained from solutions of PAs3S3·W(CO)5 (1) in CH2Cl2 or CH2Cl2/toluene and CuX (X = Cl, Br, I) in MeCN through interdiffusion techniques. Crystals of [Cu(PAs3S3)4]X (2, X = Cl; 3, X = Br) and [(Cu2I)(PAs3S3)3]I (4) were obtained and characterized by Raman spectroscopy (2) and single-crystal X-ray crystallography. The solid-state structures reveal an unexpected coordination versatility of the PAs3S3 ligand: apical phosphorus and bridging sulfur atoms interact with copper, while As···X interactions determine the dimensionality of the frameworks. The structures of 2 and 3 contain tetrahedral [(PAs3S3)4Cu]+ cations as secondary building units (SBUs), which are arranged by interactions with Cl- or Br- anions into two- and three-dimensional substructures. These interpenetrate into a (2D + 3D) polycatenane. Compound 4 is built up by a one-dimensional [(Cu2I)(PAs3S3)3]nn+ ribbon with PAs3S3 cages as P,S-linkers. The As atoms of the exo PAs3S4 linkers interact with iodide counterions (3.35 < d(As-I) < 3.59 Å). The resulting two-dimensional layer is organized by weak As···I interactions (d(As-I = 3.87 Å) into a 3D network. [ABSTRACT FROM AUTHOR]

The role of the diheme cytochrome b (HoxZ) subunit in the electron transfer pathway of the membrane-bound [NiFe]-hydrogenase (MBH) heterotrimer from Ralstonia eutropha H16 has been investigated The MBH in its native heterotrimeric state was immobilized on electrodes and subjected to spectroscopic and electrochemical analysis. Surface enhanced resonance Raman spectroscopy was used to monitor the redox and coordination state of the HoxZ heme cofoctors while concomitant protein film voltammetric measurements gave insights into the catalytic response of the enzyme on the electrode. The entire MBH heterotrimer as well as its isolated HoxZ subunit were immobilized on silver electrodes coated with self-assembled monolayers of ω-functionalized alkylthiols, displaying the preservation of the native heme pocket structure and an electrical communication between HoxZ and the electrode. For the immobilized MBH heterotrimer, catalytic reduction of the HoxZ heme cofactors was observed upon H2 addition. The catalytic currents of MBH with and without the HoxZ subunit were measured and compared with the heterogeneous electron transfer rates of the isolated HoxZ. On the basis of the spectroscopic and electrochemical results, we conclude that the HoxZ subunit under these artificial conditions is not primarily involved in the electron transfer to the electrode but plays a crucial role in stabilizing the enzyme on the electrode. [ABSTRACT FROM AUTHOR]

In this work, we establish the use of surface-enhanced Raman scattering (SERS) as a label-free analytical technique for the direct detection of G-quadruplex formation. In particular, we demonstrate that SERS analysis allows the evaluation of the relative stability of G quadruplexes that differ for the number of G tetrads and investigate several structural features of quadruplexes, such as the orientation of glycosidic bonds, the identification of distortions in the sugar-phosphate backbone, and the degree of hydrogen-bond solvation. Herein, the fluctuation of the SERS spectra, due to the specific interaction of vibrational modes with the SERS-active substrate, is quantitatively analyzed before and after quadruplex formation. The results of this study suggest a perpendicular orientation of the quadruplexes (with or without the 3'-tetra end linker) with respect to the silver colloidal surface, which opens new perspectives for the use of SERS as a label-free analytical tool for the study of the binding mode between quadruplexes and their ligands. [ABSTRACT FROM AUTHOR]

The article presents a science experiment to help second-year organic chemistry students understand the classic binary liquid-vapor phase diagram experimental techniques through hands-on experience. It states that students can explore the significant subject areas by using Raman spectroscopy as a medium of detection and quantum chemistry. Moreover, a list of materials is given, along with preparation and safety considerations, specific procedures, and discussion topics.

Protein-based biopharmaceuticals are becoming increasingly widely used as therapeutic agents, and the characterization of these biopharmaceuticals poses a significant analytical challenge. In particular, monitoring posttranslational modifications (PTMs), such as glycosylation, is an important aspect of this characterization because these glycans can strongly affect the stability, immunogenicity, and pharmacokinetics of these biotherapeutic drugs. Raman spectroscopy is a powerful tool, with many emerging applications in the bioprocessing arena. Although the technique has a relatively rich history in protein science, only recently has Raman spectroscopy been investigated for assessing posttranslational modifications, including phosphorylation, acetylation, trimethylation, and ubiquitination. In this investigation, we develop for the first time Raman spectroscopy combined with multivariate data analyses, including principal components analysis and partial least-squares regression, for the determination of the glycosylation status of proteins and quantifying the relative concentrations of the native ribonuclease (RNase) A protein and RNase B glycoprotein within mixtures. [ABSTRACT FROM AUTHOR]

We report implementation of two powerful characterization tools, in situ secondary ion mass spectrometry (SIMS) and ex situ surface enhanced Raman spectroscopy (SERS), in analyzing surfaces modified by ion soft landing (SL). Cations derived from Rhodamine fiG are soft landed Onto Raman-active silver colloidal substrates and detected using SERS. Alternatively and more conveniently, high-quality SERS data are obtained by spin coating a silver colloidal solution over the modified surface once SL is complete. Well-defined SERS features are observed for Rhodainine 6G in as little as 15 mm of ion deposition. Deposition of ∼3 pmol gave high-quality SERS spectra with characteristic spectroscopic responses being derived from just ∼0.5 fmol of material. Confocal SERS imaging allowed the enhancement to be followed in different parts of deposited dried droplets on surfaces. Characteristic changes in Raman spectral features occur when Rhodamme 6G is deposited under conditions that favor gas-phase ion fragmentation. Simultaneous deposition of both the intact dye and its fragment ion occurs and is confirmed by SIMS analysis. The study was extended to other Raman active surfaces, induding Au nanostar and Au coated Ni nanocarpet surfaces and to SL of other molecules induding fluorescein and methyl red. Overall, the results suggest that combination of SERS and SIMS measurements are effective in the characterization of surfaces produced by ion SL with significantly enhanced molecular specificity. [ABSTRACT FROM AUTHOR]

A detailed characterization of structural analysis and energy transfer (ET) process in Tm3+ doped germanate glasses has been presented. The thermal stability and Raman spectroscopic analysis of the host glass structure has been discussed. It is observed that replacing GeO2 by Ga2O3 resulted in decreasing of glass transition temperature and largest phonon energy. Increasing concentration of Ga2O3 decreases the density of cross, linking of the germanate glass network, and weaker Ga--O bonds result in lower phonon energy. The influences of the concentrations of Ga2O3 and the glass structure on the ET have also been analyzed. The extended overlap integral method is used to calculate the microparameters of the energy transfer and the critical distance. The results show that the transfrence Tm → Tm (³H3 ³H6 → ³H6 ³H3) energy migration is not phonon dependent in the quasiresonant processes, while the cross relaxation Tm → Tm (³H4, ³H6 → ³F4, ³F4) is a multiphonon mechanism dominated by one-phonon creation (~96%). It is demonstrated that the stretching frequencies and the ET processes become lower when increasing the concentration of Ga2O3. [ABSTRACT FROM AUTHOR]

In situ gap-mode Raman spectra were acquired in an electrochemical environment on a single-crystal gold electrode employing a Au( 100) 14,4′-biphenyldithiol (BPDT)∣Au-NP(55 nm) sandwich assembly. This geometry enabled an investigation of the influence of an applied electrochemical gate field on the conformational changes in nanojunctions, such as the torsion angle (φ) of molecules. A linear correlation between the intensity ratio IC=C/ICring and cos² φ in 4,4′-BPDT-type molecular junctions was established and subsequently utilized to estimate the potential dependence of the torsion angle of the "flexible" molecule M1 at different potentials. The latter decreases as the potential (charge) becomes more negative, resulting in better π-π coupling, which correlates with enhanced junction conductance. The demonstrated spectroelectrochemical strategy and the direct correlation of the spectro-scopic results with (single) molecular conductance studies may guide the selection and elucidation of functional molecules for potential applications in novel nanodevices. [ABSTRACT FROM AUTHOR]

Single-molecule surface-enhanced Raman spectroscopy (SMSERS) of crystal violet (CV) has been reported since 1997, yet others have offered alternative explanations that do not necessarily imply SMSERS. Recently, the isotopologue approach, a statistically significant method to establish SMSERS, has been implemented for members of the rhodamine dye family. We provide the first demonstration of SMSERS of a triphenylmethane dye using the isotopologue approach. Two isotopologues of CV are employed to create chemically identical yet vibrationally distinct probe molecules. Experimental spectra were compared extensively with computational simulations to assign changes in mode frequencies upon deuteration. More than 90 silver nanoparticle clusters dosed with a 50:50 mixture of CV isotopologues were spectroscopically characterized, and the vibrational signature of only deuterated or undeuterated CV was observed 79 times, demonstrating that the isotopologue approach for proving SMSERS is applicable to both the CV and the rhodamine systems. The use of CV, a minimally fluorescent dye, allowed direct evaluation of enhancement factors (EF), which are reported herein. Through experiment and theory, we show that molecular electronic resonance Raman (RR) and surface-enhanced Raman effects combine synergistically in SMSERS. Excluding RR effects, the EFSERS is ~109. Variations and relationships between substrate morphology and optical properties are further characterized by correlated SMSERS-localized surface plasmon resonance (LSPR)-high-resolution transmission electron microscopy (HRTEM) studies. We did not observe SMSERS from individual nanoparticles; further, SMSERS-supporting dimers are heterodimers of two disparately sized particles, with no subnanometer gaps. We present the largest collection to date of HRTEM images of SMSERS-supporting nanoparticle assemblies. [ABSTRACT FROM AUTHOR]

This paper investigates the structure of the products obtained from the polymerization of aniline with ammonium persulfate in a citrate/phosphate buffer solution at pH 3 by resonance Raman, NMR, FTIR, and UV−vis−NIR spectroscopies. All the spectroscopic data showed that the major product presented segments that were formed by a 1,4-Michael reaction between aniline and p-benzoquinone monoimine, ruling out the formation of polyazane structure that has been recently proposed. The characterization of samples obtained at different stages of the reaction indicated that, as the reaction progressed, phenazine units were formed and 1,4-Michael-type adducts were hydrolyzed/oxidized to yield benzoquinone. Raman mapping data suggested that phenazine-like segments could be related to the formation of the microspheres morphology. [ABSTRACT FROM AUTHOR]

Nanosized maghemite (below 10 nm average diameter), surface-functionalized with meso-2,3-dimercaptosuccinic acid (DMSA), was investigated with respect to the content of DMSA molecules attached onto its surface and the onset of S−S bridges due to oxidation of neighboring S−H groups. To support our investigation, we introduced the use of photoacoustic spectroscopy to monitor thiol groups (S−H) conjugated with Raman spectroscopy to monitor the disulfide bridges (S−S). The normalized intensity (NR) of the Raman feature peaking at 500 cm−1was used to probe the S−S bridge whereas the normalized intensity (NP) of the photoacoustic band-S (0.42−0.65 μm) was used to probe the S−H moiety. The perfect linearity observed in the NRversus (1 − NP) plot strongly supports the oxidation process involving neighboring S−H groups as the DMSA surface grafting coefficient increases whereas the approach used in this report allows the evaluation of the [S−H]/[S−S] ratio. The observation of the reduction of the hydrodynamic diameter as the nominal DMSA-grafting increases supports the proposed model picture, in which the intraparticle (interparticle) S−S bridging takes place at higher (lower) DMSA-grafting values. [ABSTRACT FROM AUTHOR]

We report on the characterization and detection of single metallic nanoparticles using a combination of con-elation spectroscopy and surface-enhanced resonance Raman spectroscopy (SERRS). Minimizing the number of independent characterization steps is critical to efficiently perform such an analysis. In this article, we improve upon conventional diffusion-limited approaches by implementing a flow-based system with high temporal resolution detection. The benefits of flow over diffusion measurements allow for a higher throughput of detected events resulting in shorter analysis times. The nanoparticles are sized using their rotational diffusion time calculated with a modified autocorrelation function. Experiments are performed using Au nanoparticles labeled with the reporter molecule malachite green isothiocyanate on a custom-built Raman spectrometer. [ABSTRACT FROM AUTHOR]