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Two-dimensional (2D) indium selenide (InSe) has been widely studied for application in transistors and photodetectors, which benefit from its excellent optoelectronic properties. Among the three specific polytypes (γ -, ϵ - and β -phase) of InSe, only the crystal lattice of InSe in β -phase (β -InSe) belongs to a non-symmetry point group of |$D_{6h}^4$|⁠ , which indicates stronger anisotropic transport behavior and potential in the polarized photodetection of β -InSe-based optoelectronic devices. Therefore, we prepare the stable p-type 2D-layered β -InSe via temperature gradient method. The anisotropic Raman, transport and photoresponse properties of β -InSe have been experimentally and theoretically proven, showing that the β -InSe-based device has a ratio of 3.76 for the maximum to minimum dark current at two orthogonal orientations and a high photocurrent anisotropic ratio of 0.70 at 1 V bias voltage, respectively. The appealing anisotropic properties demonstrated in this work clearly identify β -InSe as a competitive candidate for filter-free polarization-sensitive photodetectors. [ABSTRACT FROM AUTHOR]

The pn junctions significantly affect the responsivity of photodetectors (PDs). However, the enhancement mechanism of the pn junction is still unclear. Herein, operando Raman spectroscopy was employed to study PDs with NiO/TiO2 pn junctions composed of p-NiO nanoparticles (NPs) and n-TiO2 nanotube arrays (TNAs). The results suggest that the built-in potential field of the NiO/TiO2 interface decreases the charge transfer resistance and changes the vibrational frequency of the phonon modes of TiO2, which is attributed to the electron–phonon coupling effect. Operando Raman spectroscopy is proved to be a powerful tool for manufacturing highly responsive PDs. [ABSTRACT FROM AUTHOR]

Intercalation, the insertion of guest atomic and molecular entities into the architecture of a crystal, is an efficient route for generating new materials with novel properties. However, the detailed analysis of their new structure and properties is of great importance, which are still insufficient. Here, 1,2‐bis(4‐pyridyl)ethylene (BPE) intercalated PbI2 (BIP) has been investigated by Raman spectroscopy together with correlated studies of scanning electron microscope (SEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–Vis) absorption spectrum, and energy‐dispersive X‐ray spectroscopy (EDS). The Raman spectrum of intercalated compound discloses new lines at 83, 222, and 234 cm−1 with remarkable displacement of the bands at 1001, 1200, 1603, and 1640 cm−1, indicating a formation of a new crystal and the chemical interaction between the nitrogen atom of guest molecules with PbI2 host material. XRD confirmed the intercalation of guest molecules into a host matrix through the appearance of diffraction lines at lower angles that are corresponding to the enlarged unit cell in c axis. Furthermore, we also found that the PbI2 can specifically adsorb of BPE molecules, which was confirmed by an adsorption experiment revealed by adsorption capacity toward BPE is higher than 2,2‐bipyridine and 4,4‐bipyridine, suggesting the good adsorptive selectivity toward BPE by PbI2 film. This work further demonstrated our mechanism on enhanced Raman spectroscopy on PbI2. It is believed that this unusual discovery not only enables PbI2 to be a specific adsorbent, which also provides a new advance toward a better understanding of structure about PbI2. [ABSTRACT FROM AUTHOR]

Interfaces play an important role in enhancing the energy conversion performance of dye‐sensitized solar cells (DSCs). The interface effects have been studied by many techniques, but most of the studies only focused on one part of a DSC, rather than on a complete solar cell. Hence, monitoring the interface evolution of a DSC is still very challenging. Here, in situ/operando resonance Raman (RR) spectroscopic analyses were carried out to monitor the dynamics of the photovoltaic conversion processes in a DSC. We observed the creation of new species (i.e. polyiodide and iodine aggregates) in the photosensitization process. We also obtained molecular‐scale dynamic evidence that the bands from the C=C and C=N bonds of 2,2′‐bipyridyl (bpy), the S=C=N bonds of the NCS ligand, and photochemical products undergo reasonably strong intensity and frequency changes, which clearly demonstrates that they are involved in charge separation. Furthermore, RR spectroscopy can also be used to quickly evaluate the performance of DSCs. [ABSTRACT FROM AUTHOR]

The interaction of cytochrome c (Cyt c) with cardiolipin (CL) is believed to play an important role in the initial events of apoptosis. Herein, we investigate the structural changes of CL‐bound Fe2+Cyt c and the correlation with Cyt c release through surface‐enhanced Raman spectroscopy (SERS) on nickel substrates. The SERS results together with molecular dynamics simulation reveal that Fe2+Cyt c undergoes autoxidation and a relatively larger conformational alteration after binding with CL, inducing higher peroxidase activity of Cyt c and higher permeability of the CL membrane compared with those induced by the Fe3+Cyt c. The proapoptotic activity and SERS effect of the Ni nanostructures allow the in situ study of the redox‐state‐dependent Cyt c release from isolated mitochondria, which reveals for the first time that the ferrous state of Cyt c most likely plays a more important role in triggering apoptosis. [ABSTRACT FROM AUTHOR]

We examine the resonance Raman spectroscopy of the heteronuclear dimers VCo and VFe, using a mass-selected cluster source. Cluster cations are produced in a sputtering source and mass filtered with a Wien filter, then neutralized and deposited in an Ar matrix at low temperatures. For VCo we obtain the resonance Raman spectra in Ar matrix excited with 457.9, 488.0, 496.5, 501.7, and 514.5 nm laser lines. We observe Raman shifts of 459 and 916 cm[SUP-1], and we assign these lines to the fundamental and first overtone of the ground state. The resulting force constant is k[SUBe] = 3.42 mdyne/Å. Resonance Raman spectra of VFe, obtained at the same five excitation wavelengths, display Raman shifts at 423 and 836 cm[SUP-1], and we assign these to the fundamental and first overtone of the ground-state vibration. The resulting force constant is k[SUBe] = 2.94 mdyne/Å. We compare these observed force constants and configurations with those of other V-X dimers (X=Ti-Ni), as well as related isoelectronic species. The value for VFe, with 13 valence electrons, is considerably lower than its neighbors. This molecule most likely has a [SUP2]σ[SUP+] ground state, stemming from a (3dσ)[SUP2](3dπ)[SUP4](3dδ)[SUP4](4sσ)[SUP2](4s&sigm a;*)[SUP1] configuration. The higher force constant for VCo with 14 valence electrons indicates either a (3dσ)[SUP2](3dπ)[SUP4](3dδ)[SUP4](3dδ*)[SUP2](4s&sig ma;*)[SUP2] configuration with a [SUP3]σ state, or a (3dσ)[SUP2](3dπ)[SUP4](3dδ)[SUP4](3dδ*)[SUP1](4s&sig ma;*)[SUP2](4sσ*)[SUP1] configuration with a 3&Delata; state. [ABSTRACT FROM AUTHOR]

Self-assembled monolayers (SAMs) of (3-mercaptopropyl)trimethoxysilane (MPTS) were used as templates to induce the nucleation and growth of Ba(NO 3 ) 2 microcrystals. X-ray diffraction (XRD) patterns and optical microscopy images were employed to investigate the crystallinity and morphology of the microcrystals. It is interesting that the soaking direction of the templates plays an important role in the crystal growth process. When the MPTS-modified substrates were soaked in a vertical manner, square-like microcrystals with the (100) orientation were synthesized; however, when the substrates were soaked in a horizontal manner, triangular-like microcrystals with the (111) orientation were obtained. These differences may be due to the different regulatory mechanisms involved in the modulation of the crystal growth by the SAMs. These mechanistic discoveries pave a new way to control and design new crystals. Another interesting phenomenon is that the Raman intensity of the (111) facet of the triangular Ba(NO 3 ) 2 microcrystals is five times that of the (100) facet. By using this difference, the crystal facet index can be rapidly determined. [ABSTRACT FROM AUTHOR]

In this paper, a surface enhanced Raman spectra (SERS) detection platform for the widely used pesticide of triadimefon (TDF) is described. TDF is difficult to connect to the gold/silver SERS substrate, but the optical properties of the probe molecule 4-mercaptobenzoic acid (4-MBA), including the peak intensity and the peak position, are easily altered by the multiple weak interaction-assisted SERS detection platform. The limit of detection (LOD) of this method is 1.0 × 10-9 M, and the linear range is from 1.0 × 10-6 M to 1.0 × 10-9 M. The linear region is from 1.0 × 10-6 M to 1.0 × 10-9 M, described by the equation y = 884.01x + 2.24 with a correlation coefficient ( R2) of 0.9990. Interference of foreign metal ions with higher concentrations than common mineral water is too weak to the determination. Furthermore, physical insights into the phenomena and the detection mechanism were obtained and investigated theoretically. The preferential conformation of the complex and reduced density gradient (RDG) calculation results indicated that the interactions between TDF and 4-MBA consisted of multiple weak interactions through two hydrogen bonds and one van der Waals interaction. The intermolecular interaction was negative for the charge transfer from the SERS substrate to the probe molecule; thus, the peak intensity decreased. TDF interacts directly with the carboxyl of the probe molecule and consequently has an effect on the ring vibrations. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report on the resonance Raman spectroscopy of mass-selected CrFe. The molecule is isolated by sputtering a CrFe metal target, followed by mass-separation through a Wien filter. Samples are deposited in an argon matrix at 14 K. Raman spectra are obtained at several excitation wavelengths (476.5, 488.0, 496.5, 501.7, 514.5 nm) and a clear progression up to ν″=6 is obtained. Analysis results in values of ωe=166.6±0.8 cm−1 and ωexe=1.1±0.1 cm−1. This rather low frequency gives a force constant of 0.44 mdyne/A˚, indicating considerably weaker bonding than observed in either Cr2 or Fe2. [Copyright &y& Elsevier]

Raman spectra were measured for Langmuir–Blodgett (LB) films of C16NaphOH and C10AzoNaphC4N-SDS on Calcium Fluorite substrate for the first time. In order to find out favorable excitation condition, Raman spectra of the single and multi-monolayer LB films excited at different lines at 244, 514, 633 and 778 nm are recorded and compared in the present study. Raman spectrum of the monolayer LB film of C16NaphOH excited by 244 nm demonstrate that excellent signal to noise is achieved even for one monolayer LB film with an extremely short integrating time as 60 s because of being resonantly enhanced, while no meaningful spectra were recorded under the same condition for the monolayer LB film of C10AzoNaphC4N-SDS because of burning. Using a HeNe 633 nm excitation the problem with strong substrate fluorescence was partially solved, since under these conditions this fluorescence is mainly outside the fingerprint region of the LB film molecules (1000–2000 cm−1). Therefore by using the HeNe laser excitation, Raman spectra with high signal to noise ratio of LB films of C16NaphOH were collected and shown in this paper. These findings stress again the necessity to define an appropriate Raman system for this special application of LB film diagnosis. [Copyright &y& Elsevier]

Osteoarthritis (OA) is a degenerative disease, and there is currently no effective medicine to cure it. Early prevention and treatment can effectively reduce the pain of OA patients and save costs. Therefore, it is necessary to diagnose OA at an early stage. There are various diagnostic methods for OA, but the methods applied to early diagnosis are limited. Ordinary optical diagnosis is confined to the surface, while laboratory tests, such as rheumatoid factor inspection and physical arthritis checks, are too trivial or time-consuming. Evidently, there is an urgent need to develop a rapid nondestructive detection method for the early diagnosis of OA. Vibrational spectroscopy is a rapid and nondestructive technique that has attracted much attention. In this review, near-infrared (NIR), infrared, (IR) and Raman spectroscopy were introduced to show their potential in early OA diagnosis. The basic principles were discussed first, and then the research progress to date was discussed, as well as its limitations and the direction of development. Finally, all methods were compared, and vibrational spectroscopy was demonstrated that it could be used as a promising tool for early OA diagnosis. This review provides theoretical support for the application and development of vibrational spectroscopy technology in OA diagnosis, providing a new strategy for the nondestructive and rapid diagnosis of arthritis and promoting the development and clinical application of a component-based molecular spectrum detection technology. [ABSTRACT FROM AUTHOR]

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒13C‒glyphosate (hereafter: 13–GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by 13C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13–GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface. [ABSTRACT FROM AUTHOR]

We have fabricated a charge-transfer system using the self-assembly method. We find the nontotally symmetric b2modes are selectively enhanced in SERS spectroscopy and represent a laser wavelength-dependent property. [ABSTRACT FROM AUTHOR]

Innentitelbild: Direct Dynamic Evidence of Charge Separation in a Dye-Sensitized Solar Cell Obtained under Operando Conditions by Raman Spectroscopy (Angew. Keywords: charge transfer; dye-sensitized solar cells; nanotubes; Raman spectroscopy; semiconductors EN charge transfer dye-sensitized solar cells nanotubes Raman spectroscopy semiconductors 10758 10758 1 06/24/20 20200626 NES 200626 B Operando-Resonanz-Raman(RR)-Spektroskopie b wird von Z. Mao, B. Zhao, Y. M. Jung und Mitarbeitern in der Zuschrift auf S. 10872 für nichtinvasive und zerstörungsfreie mikroskopische Studien der dynamischen Grenzflächenevolutionen in farbstoffsensibilisierten Solarzellen (DSCs) unter Operando-Bedingungen genutzt. Charge transfer, dye-sensitized solar cells, nanotubes, Raman spectroscopy, semiconductors. [Extracted from the article]

The blue underglaze decorations of Chinese blue-and-white porcelains are due to the use of a cobalt-based blue pigment. Nevertheless, for a same time period and production centre, wares can present wide colour variations in both hue and intensity. Fourteen Ming samples were investigated using colorimetry, Raman spectroscopy and SEM-EDS, in order to better understand the origin of these variations. The majority of the sherds dates back to the middle 15th- early 16th century. The chromogenic mechanism of the hue and intensity variations appears to be complex and multifactorial. Six main factors have been identified: the elemental composition of the pigment particles, in particular the Fe/Co ratio, the pigment spinel structure, the size as well as the distribution of the colouring particles, the environment of the pigment particles and the colour of the glaze. [ABSTRACT FROM AUTHOR]

Eighteen Chinese painted enamelled porcelains and three Chinese enamelled Yixing stonewares dated to the 16th to 19th centuries and kept at the Musée national des arts asiatiques-Guimet (MNAAG), have been analysed with a mobile Raman set-up to identify their enamelling technology. Different Grand Feu (leadless or lead-poor colourless and blue enamel) and Petit Feu (lead-rich red (hematite), yellow and green (Pb-Sn/Sb/X pyrochlore) and black enamels) glazes were respectively identified on wares from the wucai group , the Famille verte group, and the huafalan g group. Calcium phosphate was detected in a 17th century vase as a rare opacifier. Cassiterite was identified in the light green glaze of an imperial huafalang bowl dated to the final period of the Kangxi reign (1662–1722), ca. the 1st quarter of the 18th century. Lead arsenate was identified in the blue glaze of two artefacts, a huafalang bowl and a painted enamel water dropper, and in the blue enamel of a 19th century Yixing teapot. Lead arsenate found in some of the blue enamels appears to arise from the arsenic content in Erzgebirge cobalt ores (Saxony) and not due to voluntary addition. This may prove the use of raw materials or enamel powder imported from Europe in developing these opaque colours. The use of lead arsenate as white opacifier is clear for a water dropper bearing the Yongzheng emperor's mark (r. 1723–1735). The technological palette appears different for the artefacts expected to originate from the same period and provenance (imperial workshop) which is consistent with a period of intense innovation, open to technological skill from abroad – i.e. from French/European painted enamel technology – as revealed by ancient French (Jesuits) and Chinese historical reports. [ABSTRACT FROM AUTHOR]

Intercalation, the insertion of guest atomic and molecular entities into the architecture of a crystal, is an efficient route for generating new materials with novel properties. However, the detailed analysis of their new structure and properties is of great importance, which are still insufficient. Here, 1,2‐bis(4‐pyridyl)ethylene (BPE) intercalated PbI2 (BIP) has been investigated by Raman spectroscopy together with correlated studies of scanning electron microscope (SEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–Vis) absorption spectrum, and energy‐dispersive X‐ray spectroscopy (EDS). The Raman spectrum of intercalated compound discloses new lines at 83, 222, and 234 cm−1 with remarkable displacement of the bands at 1001, 1200, 1603, and 1640 cm−1, indicating a formation of a new crystal and the chemical interaction between the nitrogen atom of guest molecules with PbI2 host material. XRD confirmed the intercalation of guest molecules into a host matrix through the appearance of diffraction lines at lower angles that are corresponding to the enlarged unit cell in c axis. Furthermore, we also found that the PbI2 can specifically adsorb of BPE molecules, which was confirmed by an adsorption experiment revealed by adsorption capacity toward BPE is higher than 2,2‐bipyridine and 4,4‐bipyridine, suggesting the good adsorptive selectivity toward BPE by PbI2 film. This work further demonstrated our mechanism on enhanced Raman spectroscopy on PbI2. It is believed that this unusual discovery not only enables PbI2 to be a specific adsorbent, which also provides a new advance toward a better understanding of structure about PbI2. [ABSTRACT FROM AUTHOR]

Post-translational modifications (PTMs) modulate the function of proteins and regulate most aspects of cellular functions. The qualitative and quantitative analysis of PTMs present comprehensive insights into biological regulation at the protein level, which is indispensable but challenging. Owing to its high sensitivity and specificity, enhanced Raman spectroscopy (ERS) has attracted increasing interest in the analysis of PTMs. In this review, we focus on resonance, surface-enhanced, and tip-enhanced Raman scattering-based techniques for the identification of versatile PTMs. Direct and indirect strategies for site-specific protein modifications are introduced, and the strengths and shortcomings of related approaches are outlined. Moreover, studies on monitoring PTM enzyme activity are discussed. Finally, we highlight current challenges and perspectives in detecting PTMs based on ERS. This review provides both theoretical and experimental references for researchers who devote efforts to the fast-growing research on ERS-based investigations of PTMs. Image 1 • A review on enhanced Raman spectroscopy for protein post-translational modifications (PTMs) is presented. • Latest advances in enhanced Raman scattering-based PTM analysis and related enzymes activity analysis are summarized. • Current challenges and perspectives in further enhanced Raman based PTM studies are highlighted. [ABSTRACT FROM AUTHOR]

In this study, we have investigated the effect of the surface morphologies of the zinc oxide (ZnO) substrates on surface enhanced Raman spectroscopy (SERS). During synthetic process, the self-assembly monolayers (SAMs) with different terminal groups are used as templates to induce the nucleation and growth of Zn(NO 3 ) 2 ·6H 2 O crystals, then different morphologies micro-nano ZnO powders are obtained by annealing Zn(NO 3 ) 2 ·6H 2 O crystals at 450 °C. The products obtained at different conditions are characterized by means of X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM) and Raman spectra. The as-prepared ZnO micro-sized particles have been used the efficient Surface enhanced Raman scattering (SERS) substrates, and the SERS signals of 4-mercaptopyridine (Mpy) probe molecules are much influenced by the morphologies of the ZnO structures. Results indicated that the more (0001) facets appear in the of ZnO morphology, the greater degree of charge-transfer (PCT) for the SERS enhancement on the surface of semiconductors is achieved. The chemical interaction between ZnO structures and Mpy molecules plays a very important role in the SERS enhancement. [ABSTRACT FROM AUTHOR]

Given the strong hydration propensity of fluoride ions, it is difficult to detect fluoride, especially inorganic fluoride, in aqueous samples. Resolving the issue of fluoride detection in aqueous samples is a scientific undertaking of great practical significance. Herein, we propose a new method for the sensitive and selective detection of fluoride in aqueous samples without the addition of organic solvents. The method involves surface-enhanced Raman spectroscopy using 1,4-diketo-3,6-diphenylpyrrolo[3,4- c ]pyrrole (DPP) compounds and Ag nanoparticles. The method is based on a diketopyrrolopyrrole compound linked to 1-butyl iodide (DPP1), which can sense fluoride sensitively and selectively. When DPP1 was combined with Ag NPs and reacted with tetrabutylammonium fluoride or inorganic fluoride in aqueous samples, an obvious Raman enhancement was obtained at the excitation wavelength of 633 nm. This response arises because the introduction of fluoride anions into the system changes the molecular orientation of DPP1 on the Ag NP substrate from horizontal to vertical, inducing a signal enhancement in the Raman spectrum. This system can detect inorganic fluoride at concentrations as low as 1.0 μmol L −1 (0.018 ppm), which is far below the public health service recommended levels for drinking water (0.7–1.2 ppm). Furthermore, using the proposed method, a linear response for fluoride in the concentration range of 1.0 × 10 −3 –1.0 × 10 −6 mol L −1 was obtained, which makes fluoride detection possible in practical samples, such as fluoride-containing toothpaste. [ABSTRACT FROM AUTHOR]

Potassium ions play pivotal roles in biological systems. A simple and effective Raman scattering-based protocol for the detection of physiological potassium ions level in human serum has been developed. We employed sodium cobaltinitrite, which can react with potassium to form potassium-sodium cobaltinitrite. Combining hydrophobic surface and the Raman scattering for potassium detection, highly reproducible Raman spectra of the potassium-sodium cobaltinitrite can be obtained with highly sensitivity. The characteristic Raman peak of potassium-sodium cobaltinitrite was used to distinguish it from other kinds of matter, and its intensity was used to monitor the amounts of potassium ions in human serum. Because of the contribution of the hydrophobic surface aggregation to the Raman, this protocol has great potential for practical detection of the potassium in human serum and has extended the measuring potential use in the detection of potassium in human serum by spectrum method. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid perovskite as SERS substrate improves spectral signal-to-noise ratio by narrowing the FWHM of adsorbed molecular spectrum. [Display omitted] • The SERS profile of CH 3 NH 3 PbBr 3 substrate displays high similarity with the bulk Raman spectra, its FWHM is exceeding narrow. • The significantly increased SNR of the probe molecules indicates that the substrate helps to improve the quantitative analysis capability of the SERS technology and alleviate the background-related problems. • The CH 3 NH 3 PbBr 3 has the advantage of maintaining the conformation and orientation consistency of adsorbed molecules. • The CH 3 NH 3 PbBr 3 substrate possesses specific recognition ability that has the same enhancement effect for a series of pyridine-containing probe molecules. Spectra in surface-enhanced Raman scattering (SERS) are always accompanied by a continuous emission known as "background", which complicates the analysis with a poor signal-to-noise ratio (SNR), especially for qualitative and quantitative detection. Here, the SERS profile of the CH 3 NH 3 PbBr 3 substrate displays high similarity with the bulk Raman spectra, and its FWHM is exceeding narrow. The significantly increased SNR of the probe molecules indicates that the substrate helps to improve the quantitative analysis capability of the SERS technology and alleviate the background-related problems. For the CH 3 NH 3 PbBr 3 substrate, good linearity (R2 = 0.9591) in the range of 1.0 × 10-7 − 1.0 × 10-3 mol/L was obtained and the limit of detection (LOD) is 7.88 × 10-6 mol/L. The reason for this excellent performance is that the introduction of organic molecules splits the 3D CH 3 NH 3 PbBr 3 substrate to form a 2D perovskite that fixes the molecular orientation through chemical interactions. The CH 3 NH 3 PbBr 3 has the advantage of maintaining the conformation and orientation consistency of adsorbed molecules. Meanwhile, compared with the commonly used noble metal (Au, Ag) and semiconductor (ZnO, TiO 2) SERS substrates, the CH 3 NH 3 PbBr 3 substrate has obvious superiorities in both spectral peak intensity and peak shape. Furthermore, the CH 3 NH 3 PbBr 3 substrate possesses specific recognition ability that has the same enhancement effect for a series of pyridine-containing probe molecules. Finally, the enhancement mechanism is discussed according to the CT contribution. As a promising substrate for SERS technology, CH 3 NH 3 PbBr 3 will provide more possibilities for quantitative and multiplex detection in the future. [ABSTRACT FROM AUTHOR]

In this paper, 4-mercaptobenzoic acid (4-MBA/pMBA) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Density functional theory (DFT) calculations have been performed to predict the IR and Raman spectra for the molecule. In addition, Fourier transform infrared (FTIR) and Raman spectra of the compound have been obtained experimentally. Based on the modeling results obtained at the B3LYP/6-311++G ∗∗ level, all FTIR and Raman bands of the compound obtained experimentally were assigned. Our calculated vibrational frequencies are in good agreement with the experimental vales. The molecular electrostatic potential surface calculation was performed and the result suggested that the 4-MBA had two hydrogen bond donors and three hydrogen bond acceptors. HOMO–LUMO gap was also obtained theoretically at B3LYP/6-311++G ∗∗ level. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three types of DNA nanogels were assembled by the branched DNA units. • SERS has been successfully exploited for the structural analysis of DNA nanogels. • The mechanism for enhancing the SERS signal of DNA gels has been suggested. The direct characterization of DNA nanogels at the atomic level is desirable and of great significance, however, has been challenging because of structural complexity and the larger size of nanogels. Herein, we demonstrated a simple, sensitive and reliable SERS (Surface-enhanced Raman spectroscopy)-based approach towards direct monitoring microstructures, such as three types of nanogels crosslinked by DNA G-quadruplex, i-motif and GC duplex. The achievement is attributed to the detection of featured Raman bands corresponding to the formation of Watson-Crick and Hoogsteen hydrogen bonds as well as C·C+ base pairs. Importantly, this work reveals that the silver nanoparticles attaching on the surface of nanogels can form local 'hotspots' and produce high-quality of Raman spectra under the assistance of iodide, aluminum ions and dichloromethane, therefore, shows great potential for wide applications in accurate characterization of various DNA nanostructures. [ABSTRACT FROM AUTHOR]

Some functional nanomaterials can be used as both nanozymes and SERS substrates, thus a variety of nanozyme-SERS systems have been constructed, which have been broadly applicable in many fields. In this review, we will systematically present the recent development of the fabrication, properties and applications of the nanozyme-SERS systems. First, the fundamentals of the nanozymes and SERS technique have been introduced. Then, the classification of nanozyme-SERS systems is demonstrated. To further illustrate the SERS enhancement and the catalytic mechanisms, the influence factors such as light excitation, the introduction of the reducing reagents and metal ions, environmental conditions on the properties of nanozyme-SERS systems have been discussed. In the following, their applications for sensing, disease diagnosis and therapy, food safety, immunoassay, and environmental monitoring are reviewed. Finally, the challenges and perspectives to construct new nanozyme-SERS systems for more practical applications are featured. [Display omitted] • Recent progress of the surface-enhanced Raman spectroscopy to monitor nanozyme reaction are reported. • The fundamental and typical materials for nanozyme-SERS systems are introduced. • The SERS enhancement and catalytic mechanisms with the influencing factors are discussed. • The applications for the sensing and environmental monitoring are reviewed. • The challenges and future research opportunities of this field are summarized. [ABSTRACT FROM AUTHOR]

At present, fluorescence spectroscopy, ultraviolet spectroscopy and infrared spectroscopy are usually used to detect drug molecules, however the information about using Raman spectroscopy to detect drug molecules is very few. In this work normal Raman spectroscopy and surface-enhanced Raman spectroscopy were utilized to study benzylpenicillin sodium (NaBP). The results show that NaBP is close to the surface of silver substrate through the carboxyl group, and the detection limit of NaBP is reduced to 1 × 10 −7 mol/L. Accordingly, the quantitative analysis of NaBP can be carried out in the range of 1 × 10 −4 –1 × 10 −7 mol/L concentration. And it is proved that NaBP is not stable in acid and alkali conditions and the decomposition reaction is very complex. [ABSTRACT FROM AUTHOR]

Abstract: Raman and surface-enhanced Raman scattering (SERS) spectroscopy were employed to probe the interaction of the flavonol drugs, kaempferol and galangin, with human serum albumin (HSA). SERS spectra of both flavonol derivatives were obtained from a colloidal silver surface in physiological condition, based on the high performance of the enhanced substrate, the most enhanced modes of kaempferol and galangin were those with certain motions perpendicular to the metal surface. The SERS spectra were allowed to predict similar orientation geometry for both of the drugs on the colloidal surface with minor difference. In addition, both flavonols–HSA complexes were prepared in different concentration ratios and the orientated differences between kaempferol and galangin were investigated by SERS. [Copyright &y& Elsevier]

Abstract: We report on the joint application of fluorescence, ultraviolet–visible (UV–Vis) and Raman spectroscopy to the study of berberine with human serum albumin (HSA). We propose the surface-enhanced Raman scattering (SERS) technique to improve the understanding of the quenching interaction caused by berberine which could be applied in recognition process of fluorescent drugs with large biomolecules. The fluorescence and UV–Vis spectroscopic results show that the fluorescence intensity of HSA is significantly decreased in the presence of berberine, and the quenching mechanism is static. The SERS technique demonstrates clear advantages over direct measurements in physiological conditions. By means of this method, we are able to deduce important information concerning the binding property of berberine when interacting with HSA. We show the nitrogen atom is free but the dioxolane is involved in the spontaneously electrostatic inducement and subsequently hydrophobic binding. [ABSTRACT FROM AUTHOR]

Abstract: Silver oxide film was electrodeposited onto the indium tin oxide (ITO) glass. X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy were used to determine the structure. The argentic oxide was identified to be AgO. Surface enhanced Raman scattering (SERS) spectra of 4-mercaptobenzoic acid (4-MBA) were obtained on the AgO film after the 514.5-nm laser activation. Ag nanoparticles produced from the photo-active decomposition of AgO was the substrate responsible for the enhancement of Raman signal of 4-mercaptobenzoic acid. The evolution of 4-MBA SERS spectra with time was observed due to development of Ag nanoparticles against the activation time. SERS spectra of 4-MBA, p-aminothiophenol (PATP) and benzoic acid (BA) were analyzed to determine the adsorption and orientation behaviors of above molecules. Both the electromagnetic and chemical enhancement mechanisms were proposed to be responsible for the observed enhancement of Raman signals. The enhancement factor for 4-mercaptopyridine (4-MPY) was estimated on the order of magnitude of 103. [Copyright &y& Elsevier]

Abstract: The molecular geometry and vibrational frequencies of 4,4′-bipyridine (BPE) in the ground state were calculated using density functional theory (DFT) methods (B3LYP) with 6-31++G(d,p) basis set. The optimized geometric bond lengths and bond angles are obtained by DFT employing the hybrid of Beckes non-local three parameter exchange and correlation functional and Lee–Yang–Parr correlation functional. Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and near-infrared surface-enhanced Raman scattering (NIR-SERS) spectra of BPE on the silver foil substrate have been recorded. All FT-IR, FT-Raman and NIR-SERS band were assigned on the basis of the B3LYP/6-31++G(d,p) method. The vibrational frequencies obtained by DFT(3LYP) are in good agreement with observed results. The NIR-SERS of BPE excited by 1064nm laser line is little difference with that excited by visible laser line. This phenomenon is result to the increase of the contribution of CHEM enhancement effect. Surface selection rules derived from the electromagnetic enhancement model were employed to infer the orientations of BPE on the silver foil substrate surface. Some vibrational frequency which are sensitive to the planar or non-planar structure of BPE, and to the dihedral angle were concluded. [Copyright &y& Elsevier]

[Display omitted] • A fundamental analysis of 4-CPH is proposed systematically. • The protonation of 4-CPH involves a depolarization effect. • A pH-dependent frequency shift of cyano in 4-CPH is observed and interpreted. 4-Cyanophenylhydrazine (4-CPH) is an organic synthesis intermediate. To date, several products derived from 4-CPH have been well studied; however, 4-CPH itself has not been extensively investigated. Herein, we performed vibrational and theoretical analyses of 4-CPH. Density functional theory (DFT) calculations were applied to predict the IR and Raman spectra of 4-CPH, which were compared with the experimental spectra. The calculated and experimental spectral results were in good agreement, except for an abnormal transformation of the protonated 4-CPH cyano group (C≡N), which was observed in the theoretical IR spectrum. Several wavefunction analyses revealed that this transformation was due to the protonation-induced depolarization of the molecule. Moreover, we verified the applicability of 4-CPH as a probe for surface-enhanced Raman spectroscopy (SERS). We observed a pH-dependent shift in the cyano bond frequency within the silent region and determined, as a novel discovery, that this shift was induced by 4-CPH protonation. Our results provide considerable, fundamental information that confirms the potential of 4-CPH as a SERS probe. [ABSTRACT FROM AUTHOR]

Protein phosphorylation, a post-translational modification of proteins, is of vital importance in biological regulation. Highly sensitive and site-specific identification of phosphorylated proteins is a key requirement for unraveling crucial signal transduction pathways relevant to cancers and neurodegenerative disorders. Traditional detection methods, however, suffer from relying on antibodies, labels or fragmentation prior to analysis. Here, an antibody- and label-free in situ approach to fingerprint protein phosphorylation was developed based on intrinsic Raman vibrational information of phosphorylated tyrosine, serine, threonine, or histidine residues. Combining surface-enhanced Raman scattering (SERS) spectroscopy and an immobilized-metal affinity strategy, this method is ultrasensitive to discriminate a single-site phosphorylated S396 in a Tau410 protein, an important biomarker in Alzheimer's disease. The binding feasibility of phosphorylated proteins to the modified SERS-active materials is further evidenced by molecular dynamics simulations. This proof-of-concept study paves a new way for the evaluation of site-specific and intact protein phosphorylation in both fundamental mechanical investigation and clinical applications. • Fingerprinting phosphorylated proteins by SERS combined with an immobilized-metal affinity strategy. • In situ Identification without antibodies and Raman reporters. • Single-site discrimination of phosphorylated S214 or S396 in an intact Tau protein. [ABSTRACT FROM AUTHOR]