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A simple and efficient enantioselective discrimination method, especially the chirality-label-free discrimination method, for the recognition of chiral small molecules with high resolution and wide applicability has been urgently desired. Herein, achiral Au/p-aminothiophenol (PATP) substrates were prepared to link the enantiomers via coupling reactions for constructing the enantioselective discrimination system. The resultant Au/PATP/enantiomer systems displayed charge-transfer (CT)-induced surface-enhanced Raman scattering (SERS) spectra that offered distinguishable information for the systems with different chirality. The differentiated spectral signal can be amplified by regulating the applied electrode potential, leading to great enantioselective discrimination performance. Moreover, the relationship between the discrimination performance and the potential-regulated CT process was revealed by SERS, which enabled an accurate and effective enantiomeric determination for various chiral molecules, including aromatic and aliphatic small molecules. The aliphatic molecule with the shorter chain was discriminated with a higher resolution, since the longer-chain molecule in the discrimination system may cause a change in the molecular electronic structure of the PATP. In addition, the aromatic chiral molecule can be distinguished easier than the aliphatic molecules, which means that the generation of the conjugation of electrons in the aromatic molecule-involved enantiomeric systems facilitates CT-induced SERS discrimination. Our work provides guidance for the design and development of an effective enantioselective discrimination strategy with high discrimination performance in diverse application fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • F-containing groups tune the electronic microenvironment of adsorption sites. • The adsorption capacity of PCA-Nanofiber for In(III) ions reached 116.3 mg/g. • Effective charge transfer of adsorption sites promotes In(III) ions capturing. Enhancing adsorbent-adsorbate interactions via rational construction of adsorption sites is essential for the capture of the strategic metal indium. Herein, a nanofiber (PCA-Nanofiber) was successfully fabricated for In(III) ions recovery by introducing an electronegative fluorine-containing group to modulate the electronic structure of adsorption sites. Adsorption experiments exhibited that the maximum adsorption of PCA-Nanofiber for In(III) ions (116.3 mg/g) was 3.3 times higher than that of the pre-regulated nanofiber, exceeding most of the reported adsorbents. The PCA-Nanofiber maintained stable performance in five consecutive adsorption–desorption experiments and exhibited excellent selectivity. Furthermore, advanced spectroscopic characterization revealed that the adsorbed complex presented in a six-coordinated octahedral configuration, resembling an anti-triangular prism configuration centered on In(III) ions. The density functional theory demonstrates that the excellent adsorption performance benefits from the electronegative F atoms modulating the electronic microenvironment of the adsorption sites and optimizing the band-gap energy for charge migration, resulting in efficiently driven charge transfer. This work offers ideas for the rational design of adsorption sites in nanofiber from the perspective of regulation of electronic microenvironmental. [ABSTRACT FROM AUTHOR]

The photoelectric conversion efficiency (PCE) of dye‐sensitized solar cells (DSSCs) can be remarkably improved by optimizing the catalytic activity and charge transfer ability of the counter electrode (CE) materials. The attentive hotspots of CE catalysts for DSSCs are to design multifunctional materials that balance the fabrication cost, environmental friendliness, PCE, and electrochemical stability, then to achieve the substitution of the benchmark Pt. In this review, the four effective strategies are highlighted for further improving the photovoltaic performance of the DSSCs based on low‐cost CE materials, such as heteroatom‐doped materials, development of noble metal‐free chalcogenides with well‐controlled facets, construction of heterostructure, and synthesis of composites with a synergistic effect. In some typical examples, the influence of these strategies on catalytic activity, charge transfer ability, and reaction mechanism are elucidated by the theoretical calculation. Then the research opportunities and the challenges for the high‐efficiency DSSCs based on low‐cost CE materials are presented. [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]

A novel carbon/BiOBr (C/BiOBr) photoanode with interesting electronic structure is designed. Carbon atoms are connected with bismuth (Bi) and bromine (Br) atoms by electron interaction. Such an electron interaction changes the chemical environments of Bi and Br, so that results in enhanced visible light absorption capacity and high transfer rate of charge carriers. Photoelectrochemical cell (PEC) system has been constructed to study the photoelectrochemical property of C/BiOBr photoanode. The short-circuit current (Jsc) and open-circuit voltage (Voc) of C/BiOBr are measured to be 0.057 mA/cm2 and 0.296 V, which are higher than that in PEC with the pristine BiOBr photoanode. The proposed chemically bonded C/BiOBr photoanode offers potential for electricity generation and pollutants degradation. [ABSTRACT FROM AUTHOR]

A versatile and robust chiral discrimination strategy for small aromatic compounds is of significant importance in multidisciplinary fields. However, most current methods lack either the sufficient sensitivity for recognizing the chirality of the target molecules or their molecular specificity information. We have developed a versatile and chiral‐label‐free surface‐enhanced Raman scattering (SERS)‐based chiral discrimination sensing system for small aromatic molecules, where the molecular structural specificity and enantioselectivity can be given synchronously in a single SERS spectrum. More than 10 types of chiral aromatic molecules were successfully identified by using this system. This work has enormous potential for recognizing chiral products effectively in sophisticated systems, especially in the fields of chiral synthesis and chiral catalysis. [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]

A remarkable enhancement of Raman scattering is achieved by submicrometer‐sized spherical ZnO superstructures. The secondary superstructures of ZnO particles with a uniform diameter in the range of 220–490 nm was formed by aggregating ca. 13 nm primary single crystallites. By engineering the superstructure size to induce Mie resonances, leading to an electromagnetic contribution to the SERS enhancement. Meanwhile, a highly efficient charge‐transfer (CT) contribution derived from the primary structure of the ZnO nanocrystallites was able to enhance the SERS signals as well. The highest Raman enhancement factor of 105 was achieved for a non‐resonant molecule by the synergistic effect of CT and Mie resonances. The Mie resonances scattered near‐field effect investigated in the present study provides not only an important guide for designing novel SERS‐active semiconductor substrates, but also a coherent framework for modelling the electromagnetic mechanism of SERS on semiconductors. [ABSTRACT FROM AUTHOR]

Interfacial charge transfer (CT) is of interest owing to its effect on the performance of molecular photovoltaic (PV) devices. The characteristics and structures of interfacial materials, such as TiO2 nanoparticles (NPs) in some solar cells, are employed to adjust the CT process. In this study, three kinds of interfacial systems, including a solar cell‐like TiO2‐Ag‐ p‐mercaptopyridine (MPY)‐ iron phthalocyanine (FePc) system, are compared to investigate the interfacial CT process using surface‐enhanced Raman scattering (SERS) spectroscopy. The SERS results show the significance of TiO2 NPs in the system on altering the direction and path of the interfacial CT, which is closely associated with the CT enhancement contribution to SERS in such an interfacial system. SERS spectroscopy is expected to be a promising technique for the exploration and estimation of the interfacial CT behavior in PV devices, which may further extend the applications of SERS in the field of solar cells. [ABSTRACT FROM AUTHOR]

Abstract: The differences between electromagnetic enhancement and chemical enhancement in surface‐enhanced Raman scattering (SERS) and their deep insight are very important and valuable for the explanation of spectral behaviors and the practical application of SERS technique. In this work, the typical semiconductor substrate TiO2 nanoparticles and noble‐metal substrate Ag colloid were selected as two representative SERS‐active substrates to investigate the differences between the electromagnetic (EM) mechanism and the charge‐transfer (CT) mechanism using 4‐mercaptobenzoic acid as probe molecule. The 4‐mercaptobenzoic acid molecules on two substrates exhibit the obvious differences in spectral behavior and signal intensity of SERS as well as the detectability, which can be attributed to the essential differences between the EM mechanism and the CT mechanism. The EM enhancement more depends on the behavior of the substrate, which more tends to be nonselective for the adsorbed molecules and their enhancement. The CT enhancement not only depends on the behavior of the substrate but also depends on the behavior of the adsorbed molecule due to the CT between substrate and molecule, which more tends to be selective for the adsorbed molecules and their enhancement. Moreover, it is also proved that the semiconductor (TiO2) SERS‐active substrate is characterized by the high stability and the recyclability. [ABSTRACT FROM AUTHOR]

We investigated the CT process between a 4-mercaptobenzoic acid (4-MBA) monolayer and TiO2 NPs under high pressure using surface-enhanced Raman scattering (SERS). Employing the CT enhancement mechanism of semiconductors, we explore the CT process and explain how the pressure affects the process in the 4-MBA@TiO2 system. [ABSTRACT FROM AUTHOR]

In this paper, anatase and rutile TiO2 nanoparticles as well as their mixed crystal phase structure TiO2 nanoparticles were synthesized by a sol-hydrothermal method, and were served as active substrates for surface-enhanced Raman scattering (SERS) study. The results show that the 4-mercaptobenzoic acid probe molecules exhibit different degree SERS enhancements on the surface of different phase structure TiO2 nanoparticles. The mixed crystal structure TiO2 with an appropriate proportion of anatase and rutile phase is favourable to SERS enhancement of adsorbed molecules. These are mainly attributed to the contributions of the TiO2-to-molecule charge transfer mechanism and the mixed crystal effect. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Efficient and generic enantioselective discrimination of various chiral alcohols is achieved by using surface-enhanced Raman scattering (SERS) spectroscopy through charge-transfer (CT) contributions. The relative intensities of the peaks in the SERS spectra of a chiral selector are strongly dependent on the chirality of its surroundings. This highly distinct spectral discrepancy may be due to the tendency of chiral isomers to form intermolecular hydrogen-bonding complexes with the chiral selector in different molecular orientations, resulting in different CT states and SERS intensities of the adsorbates in the system. This study opens a new avenue leading to the development of novel enantiosensing strategies. A particular advantage of this approach is that it is label-free and does not employ any chiral reagents, including chiral light. [ABSTRACT FROM AUTHOR]

The effect of the ZrO2 crystal form on surface-enhanced Raman scattering (SERS) activity was studied. The ratio of the tetragonal (T) and monoclinic (M) phases of ZrO2 nanoparticles (ZrO2 NPs) was controlled by regulating the ratio of two types of additives in the hydrothermal synthesis method. The SERS intensity of 4-mercaptobenzoic acid (4–MBA) was gradually enhanced by changing the M and T phase ratio in ZrO2 NPs. The degree of charge transfer (CT) in the enhanced 4–MBA molecule was greater than 0.5, indicating that CT was the main contributor to SERS. The intensity of SERS was strongest when the ratio of the T crystal phase in ZrO2 was 99.7%, and the enhancement factor reached 2.21 × 104. More importantly, the proposed study indicated that the T and M phases of the ZrO2 NPs affected the SERS enhancement. This study provides a new approach for developing high-quality SERS substrates and improving the transmission efficiency of molecular sensors. [ABSTRACT FROM AUTHOR]

In this paper, an Ag/MoO3 composite system was cosputtered by Ar plasma bombardment on a polystyrene (PS) colloidal microsphere array. The MoO3 formed by this method contained abundant oxygen vacancy defects, which provided a channel for charge transfer in the system and compensated for the wide band gap of MoO3. Various characterization methods strongly demonstrated the existence of oxygen vacancy defects and detected the properties of oxygen vacancies. 4-Aminothiophenol (p-aminothiophenol, PATP) was used as a candidate surface-enhanced Raman scattering (SERS) probe molecule to evaluate the contribution of the oxygen vacancy defects in the Ag/MoO3 composite system. Interestingly, oxygen vacancy defects are a kind of charge channel, and their powerful effect is fully reflected in their SERS spectra. Increasing the number of charge channels and increasing the utilization rate of the channels caused the frequency of SERS characteristic peaks to shift. This interesting phenomenon opens up a new horizon for the study of SERS in oxygen-containing semiconductors and provides a powerful reference for the study of PATP. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) is a powerful tool in charge transfer (CT) process research. By analyzing the relative intensity of the characteristic bands in the bridging molecules, one can obtain detailed information about the CT between two materials. Herein, we synthesized a series of Au nanorods (NRs) with different length-to-diameter ratios (L/Ds) and used these Au NRs to prepare a series of core–shell structures with the same Cu2O thicknesses to form Au NR–4-mercaptobenzoic acid (MBA)@Cu2O core–shell structures. Surface plasmon resonance (SPR) absorption bands were adjusted by tuning the L/Ds of Au NR cores in these assemblies. SERS spectra of the core-shell structure were obtained under 633 and 785 nm laser excitations, and on the basis of the differences in the relative band strengths of these SERS spectra detected with the as-synthesized assemblies, we calculated the CT degree of the core–shell structure. We explored whether the Cu2O conduction band and valence band position and the SPR absorption band position together affect the CT process in the core–shell structure. In this work, we found that the specific surface area of the Au NRs could influence the CT process in Au NR–MBA@Cu2O core–shell structures, which has rarely been discussed before. [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]

LiNi 0.8 Co 0.15 Al 0.05 O 2 is considered as a representative layer-structured cathode material. Decreasing residual lithium (LiOH and Li 2 CO 3) on its surface is the main challenge to improve cycling performance for commercial application. In this study, a dry and low-temperature fluorination (350 °C) method was proposed to modify LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode. The effects of fluorine content on the microstructure, surface composition and electrochemical properties of the cathode were extensively studied. The results showed that fluorination had multi-functions: (i) decreasing the lithium residues and generating amorphous LiF coating layer on the particle surface, (ii) restraining the diffusion of metal ions conveyed in the electrolyte, particularly at high temperature, (iii) retarding the increase of charge transfer impedance, and (iv) maintaining the structural stability of electrode during extended cycles. Electrochemical test results indicated that the sample fluorinated with 1.0 mol% F exhibited excellent cycling performance with the capacity retention of 93.9% after 100 cycles at 1 C, showing dramatical improvement compared with that of the pristine cathode (86.2%). This designed low-temperature dry fluorination process is expected to be practically applicable in other nickel-rich cathodes. Unlabelled Image • A low-temperature dry fluorination is adapted to reduce residual lithium of NCA. • LiF nanolayer is coated on NCA surface without destroying hexagonal layer structure • LiF can inhibit side reaction and gas evolution, and improve structural stability. • F addition has impact on composition, microstructure and electrochemical property. • Fluorinated NCA shows enhanced cyclic capacity retention and low R ct increase. [ABSTRACT FROM AUTHOR]

Innenrücktitelbild: Enhanced Raman Scattering by ZnO Superstructures: Synergistic Effect of Charge Transfer and Mie Resonances (Angew. Können als hoch effiziente, SERS-aktive (SERS=oberflächenverstärkte Raman-Streuung) Substrate genutzt werden, die W. Ji, B. Zhao, Y. Ozaki et al. in ihrer Zuschrift auf S. 14594 beschreiben. Die Superstruktur ermöglicht einen Synergieeffekt für die SERS-Verstärkung durch Kopplung von Ladungstransfer und Mie-Resonanz, was zu einem Verstärkungsfaktor von über 10 SP 5 sp führt. [Extracted from the article]

Metal@semiconductor core-shell heterostructure with strong exciton-plasmon coupling can integrate multiple functions of each component and exhibit extraordinary benefits in the optical, catalytic, electrical, and magnetic properties due to its excellent synergistic properties at the heterointerfaces. In our work, hollow gold nanoparticles (HGNs)- 4-mercaptobenzoic acid (MBA) @ZnS core-shell heterostructure with the adjustable shell thickness (t shell) of ZnS varied from 1 to 19 nm were successfully prepared for the first time by low temperature and simple two-step method. Here, we report our findings that the surface enhanced Raman scattering (SERS) spectral intensity of HGNs-MBA@ZnS under the 633 nm excitation correlates with the t shell of ZnS, and the experimental results are consistent with theoretical studies. Furthermore, we also investigated the excitation wavelength-dependent SERS enhancement mechanism of HGNs-MBA@ZnS (t shell = 2 nm) and the result showed that the near-field enhancement and plasmon-induced interfacial charge transfer transition (PICTT) synergistically increase the SERS intensity under the excitation line at 633 nm. Our work not only provides guidance for the design and synthesis of other important metal@semiconductor core-shell heterostructure, but presents significant insights into their SERS enhancement mechanism. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • In 2 O 3 NPs were firstly used as SERS substrates. • The CT mechanism of SERS is confirmed by the spectra. • Providing new semiconductor substrates for SERS applications. Surface-enhanced Raman scattering (SERS) has outstanding merits in biochemical molecular analysis, and the development of new SERS substrates is the focus of research. Herein, In 2 O 3 nanoparticles (NPs) were synthesized by a high temperature pyrolysis method with cubic phase and small particle size at 10 nm. The structures and properties of In 2 O 3 NPs were characterized by X–ray powder diffraction (XRD), transmission electron microscope (TEM) and other characterization methods. Additionally, the SERS spectra of In 2 O 3 -MBA with the enhancement factor (EF) up to 1.22 × 104 is discussed. The results demonstrate that there is a charge transfer (CT) effect revealed between the adsorbed molecules of 4-mercaptobenzoic acid (4-MBA) and the substrates of In 2 O 3 NPs, and it could be excited by long wavelength energy. Based on the In 2 O 3 NPs, the study is beneficial to develop more potential semiconductor SERS substrates. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mg and/or Zn ions doped ZrO 2 NPs exhibited an excellent surface-enhanced Raman scattering (SERS) activity. • Numerous oxygen vacancies (O V) are generated during the doping process. • Mg/Zn-codoped ZrO 2 was used for determination of antibiotic drugs with high selectivity. Noble metal-based surface-enhanced Raman scattering (SERS)-active substrates have been developed for decades. However, nonreproducible aggregation and photoinduced molecular degradation limit the development of SERS technology. To overcome the shortcomings of noble metal-based SERS substrates, we designed ZrO 2 -based nanoparticles (NPs). By doping Mg and/or Zn ions into these ZrO 2 NPs, the SERS activity was significantly improved. Mg/Zn codoping of ZrO 2 resulted in a much higher oxygen deficiency, thereby providing a sufficient surface state energy (Ess) level to enable charge transfer (CT). The primary contribution for the Mg/Zn-codoped ZrO 2 was determined to be from the CT resonance effect, resulting in an enhancement factor (EF) as high as 104. Most importantly, the CT-induced enhancement of Raman scattering based on Mg/Zn-codoped ZrO 2 has already demonstrated some promising applications in highly sensitive quinolone antibiotic drug determination. Different kinds of quinolone antibiotic drugs can be easily identified and quantitatively analyzed with high sensitivity and reproducibility. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • SnO 2 /Cu/graphene composite is synthesized by a one-pot selective reduction method. • N 2 H 4 ·H 2 O deduces the selective reduction of Cu2+ to Cu and only hydrolysis of Sn2+. • Cu NPs promote charge transfer, compress volume stress and obstruct Sn aggregation. • Conversion reaction of Sn/Li 2 O to SnO 2 is highly reversible over 200 cycles. • SnO 2 /Cu/graphene composite demonstrates extraordinary long-term cycle stability. Abstract Low electronic conductivity and the tin coarsening caused irreversible capacity loss are the primary cause of poor cycle performances in SnO 2 materials. In this work, a ternary SnO 2 /Cu/graphene composite is synthesized by a one-pot selective reduction method to improve the cycle life of SnO 2 -based composite anode. During the liquid-phase synthesis process, the Cu2+ and Sn2+ cations are adsorbed uniformly on the surface of GO sheets under electrostatic attraction, which are then selective reduced by N 2 H 4 ·H 2 O because of its moderate reduction falling in between these two components (Eϴ (Cu 2+ /Cu) 0.34 V > Eϴ (Sn 2+ /Sn) −0.14 V). The electrochemical active SnO 2 and inactive Cu nanoparticles anchor tightly on the flexible conductive graphene sheets and locate in close proximity to each other. Cu nanoparticles can promote the charge transfer kinetics of insulating SnO 2 at the interfaces, compress the volume stress as lithium ions insertion/deinsertion, and obstruct the aggregation of metallic Sn and Li x Sn alloy, thus continuously promoting the reversibility of conversion reaction from Sn/Li 2 O to SnO 2. The as-prepared composite displays an excellent long-term cycling stability, delivering a reversible capacity of 890.6 mAh g−1 at 100 mAg−1 even after 200 cycles without any capacity decay. The excellent cyclic stability and facile liquid-phase synthesis method demonstrate the promising candidate of the Cu nanoparticles in stabilizing the reversible capacity of SnO 2 /graphene composite and its candidate in scalable application. [ABSTRACT FROM AUTHOR]

p-Aminothiophenol (PATP) is a preferred molecule in research on surface-enhanced Raman scattering (SERS) because of its unique characteristics of high spectral activity, easily induced charge-transfer (CT), and sensitivity to molecular structural changes. However, some aspects are still unclear, such as the initial steady state of PATP on noble metallic substrates without strong additional excitation with incident and/or induced electromagnetic radiation. Information about the initial steady state, especially the intrinsic CT state, is of great importance to elucidate the dynamic processes of CT and/or molecular structural changes under additional excitation. To investigate the native state of an adsorbed molecule, a suitable probe method that does not disrupt the native state of the whole system, including both molecules and substrates, is required. SERS is not applied in this context because of its use of high-energy visible and near-infrared light. Herein, a low-energy probe method, surface-enhanced infrared-absorption (SEIRA) spectroscopy, is employed as a suitable method for studying the native adsorption state of PATP on silver nanoisland films. The molecular structure and adsorption state were investigated. The intrinsic CT state received particular attention by analyzing the CT-related vibration of B 2 modes. Using Fourier transform infrared (FTIR), transmission SEIRA and reflection SEIRA spectroscopy, we explained why the relative intensities of some bands were different under different conditions. A quasi-standing orientation of PATP adsorbed on the substrates was also confirmed. More importantly, we demonstrated that there is no perceptible CT between PATP and silver nanoisland films; in contrast, CT generally occurs in a disruptive manner in SERS. Density functional theory (DFT) calculations and the selection rules for infrared (IR) transmission and reflection-absorption spectroscopy were used to analyze the spectra throughout the paper. SEIRA proved to be an effective technique to explore the native adsorption state of molecules without the excessive external disturbance induced by excitation. The results are very important in providing insight into molecules in surface-interface chemistry, enhanced spectroscopy and photoelectronics. [ABSTRACT FROM AUTHOR]

Constructing heterostructure can endow composites with many novel physical and electrochemical properties due to the built-in specific charge transfer dynamics. However, controllable fabrication route to heterostructures is still a great challenge up to now. In this work, a SiO 2 -assisted hydrothermal method is developed to fabricate heterostructured nickel sulfides/reduced graphene oxide (NiS x /rGO) composite. The SiO 2 particles hydrolyzed from tetraethyl orthosilicate could assist the surface controllable co-growth of 3D nanoflowers and 0D nanoparticles of Ni 3 S 2 /NiS decorated on reduced graphene oxide, and the possible co-growth mechanism is discussed in detail. In this composite, the heterostructured nanocomposite with different morphologies, chemical compositions and crystal structures, along with varied electronic states and band structure, can promote the interface charge transfer kinetics and lead to excellent lithium storage performances. Electrochemical measurements reveal that the NiS x /rGO composite presents 1187.0 mA h g −1 at 100 mA g −1 and achieves a highly stable capacity of 561.2 mA h g −1 even when the current density is up to 5 A g −1 . [ABSTRACT FROM AUTHOR]

4-Mercaptophenylboronic Acid (4-MPBA) plays pivotal role in various fields. The orientation and existing form of the 4-MPBA strongly depend on the pH value of the media. The general aim of this work is to obtain information about the structure changes of 4-MPBA absorbed on Ag nanoparticles in different pH environment. Surface-enhanced Raman spectroscopy (SERS) technique is a simple and rapid method to study adsorption phenomena at molecule level. The investigation is done by means of SERS. In order to interpret the experimental information, a series of SERS spectra is carried out. The relative intensities of the totally symmetric (a 1 mode) and non-totally symmetric (b 2 mode) bands in the SERS spectra of 4-MPBA change depend on the environmental pH values, which is a manifestation of charge transfer (CT) processes. The degree of charge transfer increases with the pH value of the media changing from acidity to alkalinity. The structure changes of MPBA had been carried out in different pH environment. We envision that this approach will be of great significance in related fields of 4-MPBA-involved detection. [ABSTRACT FROM AUTHOR]

In this work, carbon dots (CDs) were combined with Ag nanoparticles (NPs) by a chemical reaction to form Ag NPs/CDs hybrid, which was then used as a novel surface-enhanced Raman scattering (SERS) substrate. During the synthetic process, carboxyl groups on the surface of Ag NPs were reacted with amino groups of CDs in an amidation reaction. The D and G bands of CDs in the Ag NPs/CDs hybrid could be easily detected by SERS. By employing p -aminothiophenol (PATP) molecules as SERS probes, the Ag NPs/CDs hybrid substrate could detect PATP in diluted solutions of concentration as low as 10 −9 M. The charge transfer (CT) effect on SERS spectra with different excitation wavelengths in the prepared Ag NPs/CDs hybrid and PATP system was also investigated. It was found that addition of CDs changes the degree of CT between Ag NPs and PATP molecules. Since the prepared Ag NPs/CDs hybrid also showed a peroxidase-like activity toward the oxidation of 3,3′,5,5′-tetramethylbenzidine using H 2 O 2 , which can provide the sensitive detection of H 2 O 2 by SERS technique. [ABSTRACT FROM AUTHOR]

In this work, TiO 2 and Zn doped TiO 2 nanoparticles (Zn-TiO 2 NPs) were synthesized and served as SERS-active substrate for the detection of levofloxacin (LVFX) drug molecules. Both experimental and theoretical methods are used to study the enhanced mechanism and interaction between substrate and drug molecule. The results indicate that the LVFX is close to the substrate surface through the carboxyl group. The levofloxacin molecules adsorbed on Zn-TiO 2 NPs exhibit the largest SERS enhancement, when the Zn content is 3%, the adsorption time is 7 h and pH value is 6.78. The detection limit can be reduced to 1.29 × 10 −7 mol/L by this method. And, a quantitative detection method of LVFX can be established. There is a good linear relationship in the range of 1 × 10 −3 –1 × 10 −7 mol/L concentration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mixed valence Ce doping forms multiple doping energy levels in TiO 2 and enriches its Ess. • Multiple levels and abundant Ess greatly enhance CT efficiency from substrate to molecule for boosted SERS. • SERS EF of Ce 0.010 Ti 0.990 O 2 is 2.2 × 106 and detection limit is 10−10 mol/L. • Ce 0.010 Ti 0.990 O 2 SERS substrate shows a high uniformity and stability. Considering the variable valence characteristics of rare earth elements, they can be in a variety of valence forms coexistence. Doping of rare earth element with different valence states may produce different energy levels to tune the semiconductor energy band structure. We utilize rare earth element Ce doping TiO 2 for the development of high-performance semiconductor surface-enhanced Raman scattering (SERS) substrates based on an energy-level tuning strategy. Ce doping not only forms multiple energy levels including Ce3+ and Ce4+ metal doping energy levels in the bandgap of TiO 2 , but also enriches the surface state level of TiO 2 itself, which together promote the separation of photogenerated carriers and improve charge transfer efficiency between substrates and absorbed molecules. This endows TiO 2 semiconductor substrate with a higher SERS enhancement factor, which can reach 2.2 × 106. The detectable concentration of methylene blue can be as low as 10−10 mol/L. Moreover, the semiconductor substrate exhibits excellent uniformity and stability. This study not only provides a new strategy to develop excellent semiconductor SERS substrate with multiple energy levels, but also lays the foundation for promising practical application of semiconductor substrate. [ABSTRACT FROM AUTHOR]

A very simple method for fabricating a superhydrophobic substrate was proposed. Zn foil was first polished and then immersed into an AgNO 3 solution to obtain a silver-coated surface (Zn/Ag), which resulted in the formation of micro/nano-structures. After this substrate was immersed into a solution of 1-dodecanethiol, it exhibited superhydrophobic and low adhesion properties with a high contact angle (up to 167°) and a very low sliding angle (<2°) (Zn/Ag superhydrophobic surface). This inexpensive and facile process provides a feasible approach to the large-scale production of superhydrophobic surfaces. To better investigate the potential applications for this superhydrophobic surface, a series of surface-enhanced Raman scattering (SERS) spectra were collected as the volume of a drop that was supported on the surface of the substrate decreased. The SERS signal of the molecules in the drop changed regularly, first increasing and then decreasing in intensity, and we achieved the strongest SERS signal using this procedure, which can be utilized to improve the detection limit to a certain degree. This substrate has great potential for applications in highly sensitive SERS assays. [ABSTRACT FROM AUTHOR]

[Display omitted] • A uniform and small-sized (ca. 10 nm) core–shell Ag/o-GQDs nanohybrid are successfully prepared. • The Ag/o-GQDs show unique structure with parallel-interlaced staking of o-GQDs. • The Ag/o-GQDs exhibit excellent SERS sensitivity, biocompatibility and nanozymatic activity. • The intracellular H 2 O 2 can be accurately in situ SERS monitoring at the subcellular level. The small-sized plasmonic nanoparticles are easily internalized by cells and organelles, but usually possess poor surface-enhanced Raman scattering (SERS) activity, restricting their promising applications for intracellular SERS analysis. To break the current bottleneck of intracellular SERS application, herein, a uniform and small-sized (ca. 10 nm) core–shell Ag/oxidized graphene quantum dots (o-GQDs) nanohybrids have been prepared. The Ag/o-GQDs inherit unique features with parallel-interlaced stacking of o-GQDs as capping agent, possess the increasing and broadening plasmon adsorption and display a unique edge state charge transfer (CT) resonance in the long-wavelength region of visible light, enabling the enhanced electromagnetic (EM) and CT effect for superior SERS sensitivity at lower energy. Further, the Ag/o-GQDs demonstrate excellent biocompatibility and highly efficient nanozymatically catalytic activity, which are first put forward to integrate efficient SERS with Ag/o-GQDs nanozyme to catalyze peroxidase-like reaction for accurate sensing of the intracellular H 2 O 2 at the subcellular level. Moreover, the Ag/o-GQDs nanozyme-catalyzed reactive oxygen species (ROS) generation and the cancer cell multisubcellular-targeting capability provide a promising strategy for the synergistically catalytic therapy specifically toward tumors. This study illustrates a significant route to design an efficient small-sized noble metal/carbon nanozymatic SERS substrate, and demonstrates an exciting potential for ultrasensitive SERS bioanalysis at the subcellular level. [ABSTRACT FROM AUTHOR]

[Display omitted] • ATO NPs were firstly used as SERS substrates and conformed to the CT mechanism. • Free carrier densities in CBs of ATO NPs defected the SERS ability and CT effect. • Provides idea for improving semiconductor SERS substrates based on adjusting doping. Surface-enhanced Raman scattering (SERS) has been applied in many fields, but still has the limitation of widespread applications on semiconductor substrates. In this work, a series of antimony-doped tin oxide (ATO) nanoparticles (NPs) have been synthesized by a hydrothermal method and were used as SERS substrates for the first time. Interestingly, a charge transfer (CT) effect was revealed between the probing molecules of 4-mercaptobenzoic acid (4-MBA) and the substrates of ATO NPs, which accounts for the SERS enhancement and shows dependence to the Sb ions doping ratios in ATO NPs. By considering the energy level diagram of the ATO–MBA complexes and the doping theory of semiconductors, this phenomenon is believed to connect to the variance of the optical band gap energy (E g), which is accompanied with the changes of free charge carrier densities in conduction bands (CBs) of ATO NPs due to different doping contents. The study of the E g - or free-charge-carrier-density-dependent property of the semiconductor-based SERS provides a new point of view for the development of new semiconductor SERS substrates and also contributes to the SERS CT mechanism. [ABSTRACT FROM AUTHOR]

• A novel PS/Ag/ZIF-8 SERS substrate composite was successfully prepared. • The as-prepared PS/Ag/ZIF-8 substrate could exhibit outstanding SERS property. • The SERS behavior of the substrate exhibit a laser wavelength-dependence CT effect. In this work, the monodisperse polystyrene colloidal particles/Ag/zeolite imidazole framework (PS/Ag/ZIF-8) substrate was successfully prepared and served as SERS active substrate. The composition, structure and morphology of the PS/Ag/ZIF-8 substrates were studied by XRD, SEM, UV–Vis and XPS measurements. The main finding of this study was that the as-prepared PS/Ag/ZIF-8 substrate could exhibit outstanding SERS property when 4-mercaptobenzoic acid (4-MBA) was used as the SERS probes. The SERS mechanism was attributed to the combined effect of the electromagnetic enhancement and chemical enhancement (CT). In addition, the SERS behavior of the sandwich PS/Ag/ZIF-8 substrate exhibit a laser wavelength-dependence CT effect with changing the laser source (473 nm, 514 nm, 633 nm and 785 nm). The wavelength-dependence CT mechanism were discussed briefly in the article. The results showed that the chemical interaction in the structure is a necessary condition for occurrence of the CT. The CT process can be evaluated quantitatively by the charge transfer degree (ρ CT). Moreover, the enhancement factor (EF) of 1.23 × 106 was obtained with 4-MBA probes adsorbed on the synthesized PS/Ag/ZIF-8 substrate. More importantly, our research may open the door for developing the SERS substrate research with the well-studied metal–organic frameworks nanostructures materials. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) on organic–inorganic hybrid perovskites have been proved a promising SERS-active substrate. As its inorganic skeleton, lead iodide (PbI 2) also represents a novel semiconductor substrate material that serves as either a complement or an alternative to conventional metal-based SERS. Here, for the first time, enhanced Raman scattering (ERS) of 1,2-bis(4-pyridyl)ethylene (BPE) adsorbed on PbI 2 film is observed. To our surprise, we obtained the same ERS spectra on the PbI 2 as SERS spectra obtained on the perovskites, which demonstrates the enhancement of substrate comes from inorganic skeleton rather than organic–inorganic hybrid perovskites. Compared with the normal Raman spectrum of BPE molecules, we find the B u mode of the BPE molecule was selectively enhanced. We demonstrate that it involves a charge transfer (CT) resonance mechanism and takes place between the HOMO of BPE and the conduction band edge of PbI 2. Moreover, the PbI 2 substrate performs good reproducibility, uniformity and good Raman enhancement (EF ≥ 105). It is believed that this unusual discovery not only enables PbI 2 to be an enhanced substrate, which also provides a new advance toward a better understanding of SERS chemical mechanism. Unlabelled Image • We demonstrate inorganic skeleton as the substrate. • A molecule-to-semiconductor charge transfer mechanism is proposed. • The PbI 2 exibited good reproducibility, uniformity and good enhancement (EF≥105) [ABSTRACT FROM AUTHOR]