Application of a 2D Molybdenum Telluride in SERS Detection of Biorelevant Molecules

Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker beta-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of approximate to 10(4), as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, beta-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.Peer reviewe

Attomole enantiomeric discrimination of small molecules using an achiral SERS reporter and chiral plasmonics

Biologically important molecules span a size range from very large biomacromolecules, such as proteins to small metabolite molecules. Consequently, spectroscopic techniques which can detect and characterize the structure of inherently chiral biomolecules over this range of scale at the femtomole level are necessary to develop novel biosensing and diagnostic technologies. Nanophotonic platforms uniquely enable chirally sensitive structural characterisation of biomacromolecules at this ultrasensitive level. However, they are less successful at achieving the same level of sensitivity for small chiral molecules, with less than nanomole typical. This poorer performance can be attributed to the optical response of the platform being sensitive to a much larger volume of the near field than is occupied by the small molecule. Here we show that by combining chiral plasmonic metasurfaces with Raman reporters, which can detect changes in electromagnetic environment at molecular dimensions, chiral discrimination can be achieved for attomole quantities of a small molecule, the amino acid cysteine. The signal-to-noise, and hence ultimate sensitivity, of the measurement can be further improved by combining the metasurfaces with gold achiral nanoparticles. This indirect enantiomeric detection is 9 orders of magnitude more sensitive than strategies relying on monitoring the Raman response of target chiral molecules directly. Given the generic nature of the phenomenon,this study provides a framework for developing novel technologies for detecting a broad spectrum of small biomolecules, which would be useful tools in the field of metabolomics

Chiral Metafilms and Surface Enhanced Raman Scattering For Enantiomeric Discrimination of Helicoid Nanoparticles

Chiral nanophotonic platforms provide a means of creating near fields with both enhanced asymmetric properties and intensities. They can be exploited for optical measurements that allow enantiomeric discrimination at detection levels greater than 6 orders of magnitude than is achieved with conventional chirally sensitive spectroscopic methods based on circularly polarized light. The optimal approach for exploiting nanophotonic platforms for chiral detection would be to use spectroscopic methods that provide a local probe of changes in the near field environment induced by the presence of chiral species. Here we show that surface enhanced Raman spectroscopy (SERS) is such a local probe of the near field environment. We have used it to achieve enantiomeric discrimination of chiral helicoid nanoparticles deposited on left and right-handed enantiomorphs of a chiral metafilm. Hotter electromagnetic hotspots are created for matched combinations of helicoid and metafilms (left-left and right-right), while mismatched combinations leads to significantly cooler electromagnetic hotspots. This large enantiomeric dependency on hotspot intensity is readily detected using SERS with the aid of an achiral Raman reporter molecule. In effect we have used SERS to distinguish between the different EM environments of the plasmonic diastereomers produced by mixing chiral nanoparticles and metafilms. The work demonstrates that by combining chiral nanophotonic platforms with established SERS strategies new avenues in ultrasensitive chiral detection can be opened

Can Plasmon Change Reaction Path? : Decomposition of Unsymmetrical Iodonium Salts as an Organic Probe

Plasmon-assisted transformations of organic compounds represent a novel opportunity for conversion of light to chemical energy at room temperature. However, the mechanistic insights of interaction between plasmon energy and organic molecules is still under debate. Herein, we proposed a comprehensive study of the plasmon-assisted reaction mechanism using unsymmetric iodonium salts (ISs) as an organic probe. The experimental and theoretical analysis allow us to exclude the possible thermal effect or hot electron transfer. We found that plasmon interaction with unsymmetrical ISs led to the intramolecular excitation of electron followed by the regioselective cleavage of C–I bond with the formation of electron-rich radical species, which cannot be explained by the hot electron excitation or thermal effects. The high regioselectivity is explained by the direct excitation of electron to LUMO with the formation of a dissociative excited state according to quantum-chemical modeling, which provides novel opportunities for the fine control of reactivity using plasmon energy.Peer reviewe

Optické vlastnosti epoxydové pryskyřice dotované ionty vlastních zemin

Příspěvek popisuje vlastnosti polymerních vrstev s dotací vzácných zemin. Polymer epoxidové pryskyřice Epoxy Novolak Resin byl dotován erbiem, erbiem/ytterbiem a dysprosiem. Tyto vrstvy byly připraveny metodou rotačního lití na křemíkové substráty a na substráty z křemenného skla. U vrstev byla studována infračervená spektra (IČ), absorpční spektra a luminiscenční spektra. IČ spektra prokázala, že polymerní vrstvy s obsahem vzácných zemin obsahují O-H pásy. Absorpční spektra byla použita pro zjištění pásů, které odpovídají pásům vzácných zemin, a luminiscenční spektra byla použita pro měření luminiscence erbia a erbia/ytterbia na vlnové délce kolem 1530 nm a pro luminiscenci dysprosia kolem vlnové délky 1300 nm. Ytterbium bylo použito jako syntetizér pro polymerní vrstvy s dotací erbia jako prostředek k dosažení větší intenzity optického záření na vlnové délce 1530 nm při optickém čerpání na vlnové délce 980 nm.The paper deals with the properties of rare earth ions doped polymer layers. Polymer Epoxy Novolak Resin was doped with erbium, erbium/ytterbium and dysprosium ions. The layers were fabricated by spin-coating on silicon and quartz substrates. We have investigated infrared (IR) spectra, absorption spectra and photoluminescence spectra. IR spectra show, that polymer layers doped with rare earth ions contain the O-H group. Absorption spectra were used for the investigation of bands corresponding to rare earth ions and photoluminescence measurements were used for the investigation of erbium and erbium/ytterbium luminescence around wavelength 1530 nm and for dysprosium around 1300 nm. Ytterbium ions were used as synthesizers for polymer layers doped with erbium to achieve higher photoluminescence intensity around wavelength 1530 nm

Repeated Temperature and Humidity Stability of SERS-active Periodical Silver Nanostructure

In this work the effect of physical aging on the plasmonic properties of surface plasmon-polariton supported silver grating was studied. As physical treatment the periodical variation of external temperature, humidity and their combination was applied. It was previously expected, that the physical aging will results in the silver oxidation, redistribution, and potential worse of plasmonic properties. The oxidation processes were studied using the XPS technique, the changes of surface morphology were examined by AFM, and finally, the shift of plasmonic efficiency was checked using the SERS test

Preparation of Selective and Reproducible SERS Sensors of Hg²⁺ Ions via a Sunlight-Induced Thiol–Yne Reaction on Gold Gratings

In this contribution, we propose a novel functional surface-enhanced Raman spectroscopy (SERS) platform for the detection of one of the most hazardous heavy metal ions, Hg2+. The design of the proposed sensor is based on the combination of surface plasmon-polariton (SPP) supporting gold grating with the high homogeneity of the response and enhancement and mercaptosuccinic acid (MSA) based specific recognition layer. For the first time, diazonium grafted 4-ethynylphenyl groups have undergone the sunlight-induced thiol−yne reaction with MSA in the presence of Eosine Y. The developed SERS platform provides an extremely sensitive, selective, and convenient analytical procedure to detect mercury ions with limit of detection (LOD) as low as 10−10 M (0.027 µg/L) with excellent selectivity over other metals. The developed SERS sensor is compatible with a portable SERS spectrophotometer and does not require the expensive equipment for statistical methods of analysis

Surface Plasmon-Polariton: A Novel Way To Initiate Azide–Alkyne Cycloaddition

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