Novel Multilayer Nanostructured Materials for Recognition of Polycyclic Aromatic Sulfur Pollutants and Express Analysis of Fuel Quality and Environmental Health by Surface Enhanced Raman Spectroscopy

A novel concept of advanced SERS (surface enhanced Raman spectroscopy) planar sensors is suggested for fast analysis of sulfur-containing hazardous oil components and persistent pollutants. The main advantage of the proposed sensors is the utilization of an additional preconcentrating layer of optically transparent chitosan gel, which is chemically modified with appropriate π-acceptor compounds to selectively form charge-transfer complexes (CTCs) at the interface with nanostructured silver coatings. The CTCs shift absorption bands of polycyclic aromatic sulfur heterocycles (PASHs) and other important analytes in a controllable way and thus provide a surplus enhancement of vibration modes due to resonant Raman scattering. This novel indicator system provides multiplex determination of PASHs in different forms in a small volume of oil without any tedious sample pretreatment steps. This approach opens new possibilities of increasing either spectral and concentration sensitivity or specificity of SERS-based sensors, allowing for new developments in the fields of ecology, advanced fuel analysis, and other prospective applications

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

Solution Processing of Methylammonium Lead Iodide Perovskite from γ‑Butyrolactone: Crystallization Mediated by Solvation Equilibrium

The chemical origin of solvents typically used for preparation of hybrid lead halide perovskitesdimethyl sulfoxide (DMSO), dimethylformamide (DMF), and γ-butyrolactone (GBL)strongly influences the process of perovskite crystallization because of the formation of intermediate adducts with different structures and morphology. The composition and crystal structures of the adducts depend on the coordination and binding ability of the solvents and the ratio of the precursors. New adducts of perovskite and GBL with either an unusual cluster structure, (MA)₈(GBL)_<i>x</i>[Pb₁₈I₄₄], or an adduct, (MA)₂(GBL)₂Pb₃I₈, similar to those observed for DMF and DMSO are described for the first time. Complex equilibriums between chemical species existing in perovskite solutions are revealed by Raman spectroscopy. As a result, new features of the perovskite crystallization through intermediate adduct phases are discussed, and effective perovskite deposition pathways are suggested

WS2 nanotubes dressed in gold and silver: synthesis, optoelectronic properties, and NO2 sensing

This conference contribution is focused on decoration of WS2 nanotubes (NT-WS2) with gold and silver nanoparticles via facile routes implying direct reaction of tungsten disulfide with water-soluble AuIII and AgI species at 100oC. The underlying mechanism of these interactions will be discussed in details based on extensive studies of reaction mixtures and resulting metal–NT-WS2 nanocomposites, including thorough X-ray photoelectron spectroscopy (XPS) analysis. Surprising features in optical spectra of the designed nanocomposites would be reported, including suppression of plasmon resonance in tiny noble metal nanoparticles (< 10 nm in diameter) grown onto NT-WS2. The plasmonic features of individual gold nanoparticles on the surface of disulfide nanotube were also characterized by electron energy loss spectroscopy in scanning transmission electron microscopy mode (STEM-EELS). Photoresistive NO2-sensing response of NT-WS2 under green light illumination (Ȝmax = 530 nm) and its enhancement by plasmonic gold “nanoantennas” will be reported as well

Decoration of WS₂ Nanotubes and Fullerene-Like MoS₂ with Gold Nanoparticles

A new technique of gold nanoparticle (AuNP) growth on the sidewalls of WS₂ inorganic nanotubes (INT-WS₂) and the surface of MoS₂ fullerene-like nanoparticles (IF-MoS₂) is developed to produce metal–semiconductor nanocomposites. The coverage density and mean size of the nanoparticles are dependent on the HAuCl₄/MS₂ (M = W, Mo) molar ratio. AuNPs formation mechanism seems to involve spatially divided reactions of AuCl₄^– reduction and WS₂/MoS₂ oxidation taking place on the surface defects of the disulfide nanostructures rather than directly at the AuNP-INT/IF interface. A strong epitaxial matching between the lattices of the gold nanoparticles and the INT-WS₂ or IF-MoS₂ seems to suppress plasmon resonance in the nanocomposites with small (<10 nm mean size) AuNPs

Crystal Structure of DMF-Intermediate Phases Uncovers the Link Between CH₃NH₃PbI₃ Morphology and Precursor Stoichiometry

We found for the first time a new origin of selection of perovskite crystallization pathways from DMF solutions containing MAI and PbI₂ to present here a comprehensive study of a full set of essential intermediate phases determining the perovskite’s morphology. For all three discovered structurally different intermediate phases forming at a given precursor ratio, we refined their crystal structures by synchrotron X-ray radiation and investigated dynamics and phase assemblage in the course of decomposition. As a result, we revealed a clear correlation between the composition of the intermediate phases, peculiarities of their crystal structure, and the morphology of the final perovskite films. Using the DFT method we calculated formation enthalpies of these intermediate phases and explained the preferential precipitation of DMSO-adduct rather than DMF-adduct in an antisolvent approach. This finding opens up a possibility of design-on-demand of perovskite materials using simple soft chemistry approaches