SERS of nitro group compounds for sensing of explosives.

Detecting small concentrations of nitro-compounds surface-enhanced Raman spectroscopy (SERS) is reported. In particular, explosive analogues, such as 4-nitrophenol, 1-nitronaphthalene, and 5-nitroisoquinoline, and an explosive material (picric acid) are investigated and prepared by measurements using two different methods. One method involved mixing the analyte with plasmonic silver nanoparticles (Ag NPs) in a solution, followed by subsequent drop-casting of the mixture onto a silicon substrate.

Influence of phonon anharmonicity on Raman spectra of CuZnSn(S,Se) polycrystalline thin films through computational study.

CuZnSn(S,Se) (CZT(S,Se)) thin films exhibit the characteristics necessary to be effective absorbers in solar cells. In this report, the room temperature experimental Raman scattering spectra, recorded at different excitation wavelengths, are systematically analyzed theoretically using the results of DFT harmonic frequencies calculations at the Γ-point for various modifications of kesterite (KS), stannite (ST), and pre-mixed Cu-Au (PMCA) crystal structures. The specific anharmonism-induced features in the spectra of CZT(S,Se) crystals are identified, and the spectral lineshapes at varied strengths of anharmonic interaction are simulated.

Self-Organized SERS Substrates with Efficient Analyte Enrichment in the Hot Spots.

One of the requirements of an efficient surface-enhanced Raman spectroscopy (SERS) substrate is a developed surface morphology with a high density of "hot spots", nm-scale spacings between plasmonic nanoparticles. Of particular interest are plasmonic architectures that could enable self-localization (enrichment) of the analyte in the hot spots. We report a straightforward method of fabrication of efficient SERS substrates that comply with these requirements.

Correction: Luminescence and photoelectrochemical properties of size-selected aqueous copper-doped Ag-In-S quantum dots.

[This corrects the article DOI: 10.1039/C8RA00257F.].

SERS-substrates based on ZnO nanoflowers prepared by green synthesis.

ZnO nanoparticles (NPs) with a flower-like morphology, synthesized by an affordable colloidal route using an aqueous fungi extract of Ganoderma lucidum as a reducing agent and stabilizer, are investigated as SERS-substrate. Each "flower" has large effective surface that is preserved at packing particles into a dense film and thus exhibits an advantageous property for SERS and similar sensing applications. The mycoextract used in our low-cost and green synthesis as surface stabilizer allows subsequent deposition of metal NPs or layers.

Enhanced photoconductivity of hybrid 2D-QD MoS2-AgInS2 structures.

This study describes the fabrication of hybrid two-dimensional (2D)-quantum dot (QD) MoS2-AgInS2 photoconductive devices through the mechanical pressing of a MoS2 flake onto an AgInS2 QD film. The devices exhibit an enhanced photoresponse at both continuous and modulated optical excitations, compared with the bare MoS2 or AgInS2 layer, due to the formation of a built-in electric field near the MoS2/AgInS2 interface. The continuous wave photoresponse is significantly higher due to the effective photoconductive gain when electrons flow freely through the MoS2 flake, whereas holes are effectively trapped in AgInS2 QDs.

Influence of Thermal and Flash-Lamp Annealing on the Thermoelectrical Properties of CuZnSnS Nanocrystals Obtained by "Green" Colloidal Synthesis.

The problem with waste heat in solar panels has stimulated research on materials suitable for hybrid solar cells, which combine photovoltaic and thermoelectric properties. One such potential material is CuZnSnS (CZTS). Here, we investigated thin films formed from CZTS nanocrystals obtained by "green" colloidal synthesis.

Bactericidal activity of Ag nanoparticles biosynthesized from Capsicum annuum pericarps against phytopathogenic Clavibacter michiganensis.

Metallic nanoparticles of different compositions have already found numerous applications in various branches of industry, agriculture, and medicine. Given the well-known antibacterial activity of Ag, silver nanoparticles (AgNPs) are constantly being investigated for their promising ability to fight antibiotic-resistant pathogens. A promising candidate for AgNPs biosynthesis is chili pepper Capsicum annuum, cultivated worldwide and known for accumulating significant amounts of active substances.

Core and Shell Contributions to the Phonon Spectra of CdTe/CdS Quantum Dots.

The parameters of the shell and interface in semiconductor core/shell nanocrystals (NCs) are determinant for their optical properties and charge transfer but are challenging to be studied. Raman spectroscopy was shown earlier to be a suitable informative probe of the core/shell structure. Here, we report the results of a spectroscopic study of CdTe NCs synthesized by a facile route in water, using thioglycolic acid (TGA) as a stabilizer.

ZnO and Ag NP-decorated ZnO nanoflowers: green synthesis using aqueous extract and characterization.

Fungi produce and excrete various proteins, enzymes, polysaccharides, and secondary metabolites, which may be used as media for the "green" synthesis of metal and semiconductor nanoparticles (NPs). ZnO NPs with a flower-like morphology were synthesized by an affordable colloidal route, using an aqueous extract of as a reducing agent and stabilizer. Each individual "flower" has a large effective surface, which is preserved when the particles are close packed into a dense film, which is advantageous for numerous applications.

Raman Spectroscopy and Thermoelectric Characterization of Composite Thin Films of CuZnSnS Nanocrystals Embedded in a Conductive Polymer PEDOT:PSS.

CuZnSnS (CZTS) is an intensively studied potential solar cell absorber and a promising thermoelectric (TE) material. In the form of colloidal nanocrystals (NCs), it is very convenient to form thin films on various substrates. Here, we investigate composites of CZTS NCs with PEDOT:PSS, a widely used photovoltaics polymer.

Phonon Raman spectroscopy of nanocrystalline multinary chalcogenides as a probe of complex lattice structures.

Ternary (I-III-VI) and quaternary (I-II-IV-VI) metal-chalcogenides like CuInSor CuZnSn(S,Se)are among the materials currently most intensively investigated for various applications in the area of alternative energy conversion and light-emitting devices. They promise more sustainable and affordable solutions to numerous applications, compared to more developed and well understood II-VI and III-V semiconductors. Potentially superior properties are based on an unprecedented tolerance of these compounds to non-stoichiometric compositions and polymorphism.

Plasmonic colloidal Au nanoparticles in DMSO: a facile synthesis and characterisation.

We report a new pathway for the synthesis of plasmonic gold nanoparticles (Au NPs) in a bio-compatible medium. A modified room temperature approach based on the standard Turkevich synthesis, using sodium citrate as a reducing and stabilizing agent, results in a highly stable colloidal suspension of Au NPs in dimethyl sulfoxide (DMSO). The mean NP size of about 15 nm with a fairly low size distribution is revealed by scanning electron microscopy.

Self-assembly of colloidal single-layer carbon nitride.

We introduce a new concept of a "bottom-to-top" design of intercalate carbon nitride compounds based on the effects of self-assembly of colloidal single-layer carbon nitride (SLCN) sheets stabilized by tetraethylammonium hydroxide NEtOH upon ambient drying of the water solvent. These effects include (i) formation of stage-1 intercalates of NEtOH during the ambient drying of SLCN colloids on glass substrates and (ii) the spontaneous formation of layered hexagonally-shaped networks of SLCN sheets on freshly-cleaved mica surfaces. The dynamics of the intercalate formation was followed by X-ray diffraction allowing different stages to be identified, including the deposition of a primary "wet" intercalate of hydrated NEtOH and the gradual elimination of excessive water during its ambient drying.

Colloidal Cu-Zn-Sn-Te Nanocrystals: Aqueous Synthesis and Raman Spectroscopy Study.

Cu-Zn-Sn-Te (CZTTe) is an inexpensive quaternary semiconductor that has not been investigated so far, unlike its intensively studied CZTS and CZTSe counterparts, although it may potentially have desirable properties for solar energy conversion, thermoelectric, and other applications. Here, we report on the synthesis of CZTTe nanocrystals (NCs) via an original low-cost, low-temperature colloidal synthesis in water, using a small-molecule stabilizer, thioglycolic acid. The absorption edge at about 0.

Raman and X-ray Photoelectron Spectroscopic Study of Aqueous Thiol-Capped Ag-Zn-Sn-S Nanocrystals.

The synthesis of (Cu,Ag)-Zn-Sn-S (CAZTS) and Ag-Zn-Sn-S (AZTS) nanocrystals (NCs) by means of "green" chemistry in aqueous solution and their detailed characterization by Raman spectroscopy and several complementary techniques are reported. Through a systematic variation of the nominal composition and quantification of the constituent elements in CAZTS and AZTS NCs by X-ray photoemission spectroscopy (XPS), we identified the vibrational Raman and IR fingerprints of both the main AZTS phase and secondary phases of Ag-Zn-S and Ag-Sn-S compounds. The formation of the secondary phases of Ag-S and Ag-Zn-S cannot be avoided entirely for this type of synthesis.

Multifunctional Magneto-Plasmonic FeO/Au Nanocomposites: Approaching Magnetophoretically-Enhanced Photothermal Therapy.

Magneto-plasmonic nanocomposites can possess properties inherent to both individual components (iron oxide and gold nanoparticles) and are reported to demonstrate high potential in targeted drug delivery and therapy. Herein, we report on FeO/Au magneto-plasmonic nanocomposites (MPNC) synthesized with the use of amino acid tryptophan via chemical and photochemical reduction of Au ions in the presence of nanosized magnetite. The magnetic field (MF) induced aggregation was accompanied by an increase in the absorption in the near-infrared (NIR) spectral region, which was demonstrated to provide an enhanced photothermal (PT) effect under NIR laser irradiation (at 808 nm).

Photoinduced Enhancement of Photoluminescence of Colloidal II-VI Nanocrystals in Polymer Matrices.

The environment strongly affects both the fundamental physical properties of semiconductor nanocrystals (NCs) and their functionality. Embedding NCs in polymer matrices is an efficient way to create a desirable NC environment needed for tailoring the NC properties and protecting NCs from adverse environmental factors. Luminescent NCs in optically transparent polymers have been investigated due to their perspective applications in photonics and bio-imaging.

Ultra-small aqueous glutathione-capped Ag-In-Se quantum dots: luminescence and vibrational properties.

We introduce a direct aqueous synthesis of luminescent 2-3 nm Ag-In-Se (AISe) quantum dots (QDs) capped by glutathione (GSH) complexes, where sodium selenosulfate NaSeSO is used as a stable Se precursor. A series of size-selected AISe QDs with distinctly different positions of absorption and PL bands can be separated from the original QD ensembles by using anti-solvent-induced size-selective precipitation. The AISe-GSH QDs emit broadband PL with the band maximum varying from 1.

Mercury-indium-sulfide nanocrystals: A new member of the family of ternary in based chalcogenides.

A general synthesis approach of aqueous glutathione-capped ternary Ag-In-S, Cu-In-S, and Hg-In-S nanocrystals (NCs) is introduced, allowing the NC composition to be varied in a broad range. Ternary Hg-In-S (HIS) NCs are reported for the first time and found to have the same tetragonal chalcopyrite motif as Cu-In-S and Ag-In-S NCs, corroborated by phonon spectra, while X-ray photoelectron spectroscopic data indicate mercury to be present as Hg in the Hg-In-S NCs. Colloidal HIS and Hg-In-S/ZnS NCs showed little or no variations of the spectral width of the photoluminescence band upon NC size selection, temperature variation in a broad range of 10-350 K, deposition of a ZnS shell, or postsynthesis annealing.

Flexible plasmonic graphene oxide/heterostructures for dual-channel detection.

Graphene oxide (GO) films are deposited on flexible Kapton substrates and selectively modified to conductive reduced graphene oxide (rGO) electrodes using laser patterning. Based on this, we design, fabricate, and test a flexible sensor integrating laser-reduced GO with silver plasmonic nanostructures. The fabricated device results in dual transduction channels: for electrochemical and plasmonic nanostructure-based surface-enhanced Raman spectroscopy (SERS) detection.

The role of a plasmonic substrate on the enhancement and spatial resolution of tip-enhanced Raman scattering.

Since the first report in the early 2000s, there have been several experimental configurations that have demonstrated enhancement and spatial resolution of tip-enhanced Raman spectroscopy (TERS). The combination of a plasmonic substrate and a metallic tip is one suitable approach to achieve even higher enhancement and lateral resolution. In this contribution, we demonstrate TERS on a monolayer of MoS on an array of Au nanodisks.

Raman study of flash-lamp annealed aqueous CuZnSnS nanocrystals.

The effect of flash-lamp annealing (FLA) on the re-crystallization of thin films made of colloidal CuZnSnS nanocrystals (NCs) is investigated by Raman spectroscopy. Unlike similar previous studies of NCs synthesized at high temperatures in organic solvents, NCs in this work, which have diameters as small as 2-6 nm, were synthesized under environmentally friendly conditions in aqueous solution using small molecules as stabilizers. We establish the range of FLA conditions providing an efficient re-crystallization in the thin film of NCs, while preserving their kesterite structure and improving their crystallinity remarkably.

Nanoantenna structures for the detection of phonons in nanocrystals.

We report a study of the infrared response by localized surface plasmon resonance (LSPR) modes in gold micro- and nanoantenna arrays with various morphologies and surface-enhanced infrared absorption (SEIRA) by optical phonons of semiconductor nanocrystals (NCs) deposited on the arrays. The arrays of nano- and microantennas fabricated with nano- and photolithography reveal infrared-active LSPR modes of energy ranging from the mid to far-infrared that allow the IR response from very low concentrations of organic and inorganic materials deposited onto the arrays to be analyzed. The Langmuir-Blodgett technology was used for homogeneous deposition of CdSe, CdS, and PbS NC monolayers on the antenna arrays.