Transmission Raman Spectroscopy Research Articles

Active Surface-Enhanced Raman Spectroscopy (SERS): A Novel Concept for Enhancing Signal Contrast in Complex Matrices Using External Perturbation.

Noninvasive detection of surface-enhanced Raman spectroscopy (SERS) signals from deep within tissue represents a common challenge in many biological and clinical applications including disease diagnosis and therapy monitoring. Such signals are typically weak and not readily discernible from often much larger Raman and fluorescence background signals (e.g., from surrounding tissue). Consequently, suboptimal sensitivity in the detection of SERS signals is often achieved in these situations. Similar issues can arise in SERS measurements in other diffusely scattering samples and complex matrices. Here, we propose a novel concept, active SERS, for the efficient retrieval of SERS signals from deep within complex matrices such as biological tissues that mitigates these issues. It relies on applying an external perturbation to the sample to alter the SERS signal from nanoparticles (NPs) deep inside the matrix. A measurement with and without, or before and after, such perturbation then can provide powerful contrasting data enabling an effective elimination of the matrix signals to reveal more clearly the desired SERS signal without the interfering background and associated artifacts. The concept is demonstrated using ultrasound (US) as an external source of perturbation and SERS NPs inserted deep within a heterogeneous tissue phantom mimicking a cluster of NPs accumulated within a small target lesion. The overall SERS signal intensity induced by the applied US perturbation decreased by ∼21% and the SERS signal contrast was considerably improved by eliminating subtraction artifacts present in a conventional measurement performed at a neighboring spatial location in a heterogeneous tissue sample. Although the technique was demonstrated with SERS gold NPs with a standard Raman label, it is envisaged that active SERS NPs (both the nanoscale metal geometry and Raman label) could be specifically designed to deliver an augmented response to the external stimulus to further enhance the achievable SERS signal contrast and yield even greater improvement in detection sensitivity. The method was demonstrated using transmission Raman spectroscopy; however, it is also applicable to other Raman implementations including spatially offset Raman spectroscopy and conventional Raman spectroscopy performed both at depth and at surfaces of complex matrices.

Synthesis of MS2 (M=Mo, W) thin films by chemical solution deposition

MoS2 and WS2 as typical two-dimensional transition metal dichalcogenides have been investigated since of rich physicochemical properties. To deposit MoS2 and WS2 thin films, chemical solution deposition as a facile route had been used showing the advantages of high component controllability, low cost, sequential processing of device, easy preparation of large-size films and facile preparation of films on irregular substrates. Here, Mo1-xWxS2 (0 ≤ x ≤ 1) thin films were successfully prepared by chemical solution deposition method. The phases as well as microstructures were investigated using field emission scanning electron microscope, atomic force microscopy, transmission electron microscopy, Raman and x-ray photoelectron spectroscopy measurements. The prepared Mo1-xWxS2 thin films are used as hydrogen evolution reaction (HER) catalyst electrodes for water splitting. The Mo0·3W0·7S2 thin film catalyst shows an overpotential of 345 mV at a current density of 10 mA cm−2 and the corresponding Tafel slope of 169 mV dec−1 in 0.5 M sulfuric acid. The results will provide a facile method to deposit MX2 thin films.

Structure and exfoliation mechanism of two-dimensional boron nanosheets

Exfoliation of two-dimensional (2D) nanosheets from three-dimensional (3D) non-layered, non-van der Waals crystals represents an emerging strategy for materials engineering that could significantly increase the library of 2D materials. Yet, the exfoliation mechanism in which nanosheets are derived from crystals that are not intrinsically layered remains unclear. Here, we show that planar defects in the starting 3D boron material promote the exfoliation of 2D boron sheets—by combining liquid-phase exfoliation, aberration-corrected scanning transmission electron microscopy, Raman spectroscopy, and density functional theory calculations. We demonstrate that 2D boron nanosheets consist of a planar arrangement of icosahedral sub-units cleaved along the {001} planes of β-rhombohedral boron. Correspondingly, intrinsic stacking faults in 3D boron form parallel layers of faulted planes in the same orientation as the exfoliated nanosheets, reducing the {001} cleavage energy. Planar defects represent a potential engineerable pathway for exfoliating 2D sheets from 3D boron and, more broadly, the other covalently bonded materials.

Novel imidacloprid nanoribbons prepared by laser fragmentation/exfoliation in liquid media

The preparation of Imidacloprid (IMC) Nanoribbons by laser induced simultaneous fragmentation and exfoliation of micrometer sized IMC powders suspended in water is reported. Samples were prepared varying both the laser fluence and quantity of IMC powder. The prepared nanostructures were characterized by transmission electron microscopy (TEM), Raman spectroscopy and X-Ray Photoelectron Spectroscopy (XPS). TEM characterization showed that nearly spherical nanoparticles were obtained at the lowest fluence whereas at the highest fluence, IMC nanoribbons (IMCNR) with widths from 500 to 1000 nm and thickness of few atomic layers were obtained. Raman Spectroscopy showed the vibrational features of imidacloprid revealing that this organic molecule was preserved after laser irradiation. The XPS characterization confirms and supports the Raman results revealing that the nanoribbons were formed by the IMC organic molecule. The toxicity evaluation showed that IMCNR caused a more accelerated mortality of Drosophila melanogaster than the same dose of IMC.

Epitaxial Growth of the Large-Scale, Highly-Ordered 3D GaN-Truncated Pyramid Array Toward an Ultrahigh Rejection Ratio and Responsivity Visible-Blind Ultraviolet Photodetection.

The micro- and nanostructures of III-nitride semiconductors captivate strong interest owing to their distinctive properties and myriad potential applications. Nevertheless, challenges endure in managing the damage inflicted on crystals through top-down processes or achieving extensive control over the large-area growth of these microstructures via bottom-up methods, thereby impacting their optical and electronic properties. Here, we present novel epitaxially grown 3D GaN truncated pyramid arrays (TPAs) on patterned Si substrates, devoid of any catalyst. These GaN TPAs feature highly ordered, large-scale structures, attributed to the utilization of 3D Si substrates and thin AlN interlayers to alleviate epitaxial strains and limit dislocation formation. Comprehensive characterization via scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and cathodoluminescence attests to the superior structural and optical attributes of these crystals. Furthermore, photoluminescence and ultraviolet (UV)-visible diffuse reflectance spectroscopy reveal sharp band-edge emission and significant light trapping in the UV bands. Employing these GaN TPAs, we constructed metal-semiconductor-metal visible-blind UV photodetectors (PDs) incorporating Ti3C2 MXene as Schottky electrodes. These PDs display exceptional responsivity, achieving 5.32 × 103 mA/W at 255 nm and an ultrahigh UV/visible rejection ratio (R255nm/R450nm) approaching 106, which are 1-2 orders of magnitude higher than most recently reported works. This exploration showcases novel GaN-based microstructures characterized by uniformity, ordered geometry, and exemplary crystalline integrity, paving the way for developing optoelectronic applications.

Research on optimizing ultrasonic frequencies for efficient single-walled carbon nanotube dispersion in water using a focused ultrasonic system

Single-walled carbon nanotubes (SWCNTs) can be applied in a wide range of fields owing to their excellent mechanical rigidity, electrical conductivity, and thermal conductivity. However, their application is limited because of their strong van der Waals forces and poor dispersion owing to their hydrophobic properties. To address this problem, ultrasonic dispersion technology has been used in the industry. However, very few studies have investigated the surface damage or effectiveness of the surfactants of SWCNTs with a focus on the frequencies of specific ultrasonic equipment. In this study, the dispersibility of SWCNTs at frequencies of 270, 400, and 700 kHz was investigated using a new focused ultrasonic instrument. The dispersion stability of the samples was analyzed according to each frequency, and the SWCNT surface was studied in detail using field-emission transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The adsorption of the polymeric surfactant to the SWCNT was most observed at 270 kHz, and the dispersion stability after processing at this frequency was better than that of the other samples. Therefore, the frequency of the ultrasonic intensity has a direct effect on the surface modification of SWCNTs.

One-Pot Electrodeposition of a PANI:PSS/MWCNT Nanocomposite on Carbon Paper for Scalable Determination of Ascorbic Acid

In recent years, there has been growing demand for the monitoring of ascorbic acid levels, especially in underdeveloped populations where ascorbic acid deficiency affects up to 74% of individuals. To facilitate widespread ascorbic acid screening, we have developed a highly scalable conductive polymer nanocomposite with excellent ascorbic acid sensing performance. The material is based on polyaniline, which is deposited in a single step in the presence of polystyrene sulfonate and multi-walled carbon nanotubes onto carbon paper. The modified electrodes take advantage of the electrocatalytic properties of polyaniline toward ascorbic acid, which are boosted by the proton donating polystyrene sulfonate polymer and the high surface area of the multi-walled carbon nanotubes. The morphology and composition of the composite are characterized using field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy and the electrochemical characteristics are examined using cyclic voltammetry and electrochemical impedance spectroscopy. The modified electrode shows good ascorbic acid sensing characteristics, with a linear range of 1–400 μM, a sensitivity of 546 μA mM−1 cm−2, and a limit of detection of 0.11 μM. High performance and low cost results in a promising platform to support the widespread, cheap monitoring of ascorbic acid deficiency.

Synthesis and characterization of pristine CuO and Mg/CuO nanostructures for their anti-breast cancer and photocatalytic degradation applications: Experimental and DFT investigations

The present manuscript emphasizes the versatility of Mg-doped CuO nanostructures for environmental remediation (photocatalytic degradation of pollutants) and biomedical applications (anticancer activity) thus highlighting their potential impact in addressing societal and health challenges. The primary focus of the manuscript is the synthesis, characterization, and applications of Mg-doped CuO nanostructures. In order to meet this purpose, pure and Mg doped CuO nanostructures were synthesized using the solid-state reaction method and ball milling techniques. To characterize the prepared samples, X-ray diffraction, transmission electron microscopy, UV-Visible, photoluminescence, and Raman spectroscopy techniques were utilized. A profusion of structural defects and the reduction in crystallite size have been observed in CuO nanomaterial’s due to the dopant's complete incorporation into the CuO lattice. Additionally, the band gap of CuO has been observed to decrease as a result of Mg doping. Density functional theory was employed to simulate the effect of Mg on the properties of CuO. The efficiency of photocatalytic degradation aided by sunlight against methylene blue increased from 50.8 % to 89.5 %. MCF-7, a cell line representing human breast adenocarcinoma, was utilized to assess the cytotoxicity of Mg/CuO samples. CuO nanoparticles enriched with Mg are viable biocompatible anti-cancer agents and prospective photocatalyst for the removal of environmental pollutants from aqueous solutions, according to the findings of this study.

Enhancement of methylene blue catalytic reduction by novel green synthesized metal decorated reduced graphene oxide: Sn@rGO and Ag@rGO

Carbon-based nanocomposites (NCs) attracted much attention in heterogeneous catalysis to remove organic dyes. Herein, a novel low-cost green approach was utilized to design a reduced graphene oxide (rGO) impregnated with Sn or Ag nanoparticles (NPs) using ginger extract as a green reducing agent. The synthesized NCs were characterized utilizing X-ray diffraction (XRD), Fourier transformation infrared (FTIR), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), Raman spectroscopy, and thermal gravimetric analysis (TGA). The synthesized NCs were assessed for their catalytic reduction activity towards methylene blue (MB) dye. XRD displayed the characteristic peaks of Sn- and Ag-NPs and the reduction of GO, referring to successful NC formation. FTIR and Raman confirmed the reduction of GO and the incorporation of Sn and Ag-NPs into the GO surfaces. TEM results proved that either Sn- or Ag-NPs was uniformly dispersed on rGO sheets with average sizes of 4.129 and 7.293 nm, respectively. EDX spectra of Sn@rGO- and Ag@rGO-NCs revealed the presence of C, O, Sn, and Ag. TGA confirmed the increased thermal stability of the NCs as compared to GO. Ag@rGO-NC exhibited stronger catalytic MB reduction (97% after 10 min) than Sn@rGO-NC (80% after 20 min). To the best of our knowledge, this is the first time Sn@rGO-NC has been designed for MB catalytic reduction, which gives rise to its promising capacity for future catalytic applications.

Tailored multi-layer graphene arrays for precision detection of neurotransmitter

The development of sensitive dopamine (DA) sensors has significantly contributed to our understanding of DA-related disorders and has enabled advancements in medical diagnostics and neuroscience research. Therefore, in the present work, a novel electrochemical sensing platform was developed using multi-layer graphene arrays (MGA) modified electrodes for the selective detection of DA. The preparation of high-quality MGA was achieved using the plasma-enhanced chemical vapor deposition (PCVD) method and was confirmed using various physiochemical techniques such as transmission electron microscopy and Raman spectroscopy. The modified electrode, made of MGA, was utilized for the electrochemical detection of DA using cyclic voltammetry and amperometry i-t methods. DA’s electrochemical oxidation response and sensitivity at the MGA electrode were ≈9 and 3 times higher than observed with unmodified and commercially available multi-layer graphene-modified electrodes. The MGA sensor exhibited excellent analytical parameters for DA detection, including a wide linear range of up to 172.1 μM and a low detection limit of 1.3 nM. The sensor also demonstrated remarkable sensitivity, storage stability, and selectivity for DA detection, making it highly suitable for accurately detecting DA in medical diagnostics and neuroscience research. Furthermore, the practical application of the MGA sensor for DA detection was demonstrated in various real samples.

Facet-Dependent Surface Restructuring on Nickel (Oxy)hydroxides: A Self-Activation Process for Enhanced Oxygen Evolution Reaction.

Unraveling the catalyst surface structure and behavior during reactions is essential for both mechanistic understanding and performance optimization. Here we report a phenomenon of facet-dependent surface restructuring intrinsic to β-Ni(OH)2 catalysts during oxygen evolution reaction (OER), discovered by the correlative ex situ and operando characterization. The ex situ study after OER reveals β-Ni(OH)2 restructuring at the edge facets to form nanoporous Ni1-xO, which is Ni deficient containing Ni3+ species. Operando liquid transmission electron microscopy (TEM) and Raman spectroscopy further identify the active role of the intermediate β-NiOOH phase in both the OER catalysis and Ni1-xO formation, pinpointing the complete surface restructuring pathway. Such surface restructuring is shown to effectively increase the exposed active sites, accelerate Ni oxidation kinetics, and optimize *OH intermediate bonding energy toward fast OER kinetics, which leads to an extraordinary activity enhancement of ∼16-fold. Facilitated by such a self-activation process, the specially prepared β-Ni(OH)2 with larger edge facets exhibits a 470-fold current enhancement than that of the benchmark IrO2, demonstrating a promising way to optimize metal-(oxy)hydroxide-based catalysts.

Aminosilane assisted deposition of gold nanoparticles on Zn(OH)2 nanosheets and their application in electrochemical sensor

A facile and efficient method for systematical deposition of gold nanoparticles (AuNPs) on Zn(OH)2 nanosheets (NS) with different Zn and Au ratios was established in the presence of N-[3-(trimethoxysilyl)propyl]diethylenetriamine (TPDT silane), without adding any external reducing agents, at room temperature. Here, TPDT silane behaves as both a stabilizing and reducing agent. UV–vis absorption spectroscopy, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy-energy dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to confirm the formation of AuNPs on Zn(OH)2 NS. As the concentration of AuNPs increased, a proportional increase in both the number and size of deposited AuNPs on Zn(OH)2 NS was observed. To understand how the variation in the number and size of AuNPs affects their catalytic activity, the electrocatalytic activity of different composition ratios of Zn(OH)2-Au NS toward nitrite ions was studied using cyclic voltammetry and amperometric technique. The TPDT-stabilized Zn(OH)2-Au NS showed high electrocatalytic activity, attributed to the effective electron transfer from Zn(OH)2 NS to AuNPs, creating a synergistic effect that enhances the overall activity. The optimal Zn(OH)2-Au NS modified electrode showed an amperometric sensitivity of 5.72 nA/µM and a limit of detection of 1.2 µM for nitrite ions in water sample well below the guideline value of WHO. This demonstrates the practical applicability of this method for real-world water analysis.

Significantly improved optoelectronic performances of two-dimensional WS2(Er3+)/WSe2(Er3+) van der waals heterojunctions

Two-dimensional heterostructures with excellent properties are potential for high performance optoelectronic applications, since the ultimate thickness limit is possible to be broken with the advent of atomically thin materials. Yet the studies have also been largely constrained by the low physical doping space and absorption rates due to the atomic-thickness layers, and the efforts for high carrier concentrations and gain remain a significant challenge. Herein, high concentration of Er3+ ions are in-situ doped in WS2 and WSe2 atomic layers by chemical vapor deposition (CVD) method. The prepared layers are characterized by atomic force microscopy, transmission electron microscopy, photoluminescence (PL) spectroscopy, and Raman spectroscopy, respectively. 13–14 at% of Er3+ doping concentration in WSe2 and WS2 are examined by energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) with high consistency. A microregion fixed-point transfer technique is used to transfer the WS2(Er3+) monolayers onto the WSe2(Er3+) monolayers to form vertical van der Waals heterojunctions. Excellent performances are measured from the WS2(Er3+)/WSe2(Er3+) photodetector with the photoresponsivity of up to 67.4 A/W, external quantum efficiency of 13,202 %, and detectivity of 7.07 × 1011 Jones. Our results prove the effectiveness of Er3+ in-situ doping in WS2(Er3+)/WSe2(Er3+) heterojunctions for high-performance photodetectors.

Impact of crystallinity on thermal conductivity of RF magnetron sputtered MoS2 thin films

This study investigates the effects of sulfur atomic defects and crystallinity on the thermal conductivity of MoS2 thin films. Utilizing scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), and Raman spectroscopy, we examined MoS2 films, several nanometers thick, deposited on Si/SiO2 substrates. These films were prepared via a combination of RF magnetron sputtering and sulfur vapor annealing (SVA) treatment. Structural analyses, including cross-sectional STEM and in-plane and out-of-plane XRD measurements, revealed an increase in the S/Mo ratio and grain size of the MoS2 films following SVA treatment. Notably, the in-plane thermal conductivity of MoS2 films treated with SVA was found to be at least an order of magnitude higher than that of films without SVA treatment. This research suggests that the in-plane thermal conductivity of MoS2 thin films can be significantly enhanced through crystallinity improvement via SVA treatment.

Synthesis of multi-layer graphene oxide from HCl-treated coke and Brazilian coals by sulfuric acid thermal exfoliation and ozone oxidation

This study involved the synthesis and characterization of graphene oxide (GO) from mineral coke and bituminous coal. HCl treated and non-HCl treated ultrafine powder obtained from both precursors were treated with H2SO4, followed by thermal treatment, and oxidation with ozone and ultra-sonication for GO production. The synthesized materials were characterized using Fourier transform infrared spectroscopy (FTIR), zeta potential (ZP), particle size distribution (PSD), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results confirmed the exfoliation of the material primarily at the edges of its structure and the formation of multilayer graphene oxide (GO) from mineral coke and bituminous coal. Furthermore, it was found that carbonaceous materials with graphitic morphology are easier to exfoliate and oxidize, leading to the production of higher quality graphene oxide. Therefore, the GO synthesized from mineral coke exhibited the best quality in this study. The methodology used proposes an innovative approach, offering a faster, more economical, and environmentally friendly synthesis compared to the traditional Hummers' method, thereby adding value to other raw materials that can be utilized in this process, such as Brazilian coke and coal.

High performance antimony-rich RexSb3Te for phase-change random access memory applications

Phase-change random access memory (PCRAM) demands for high-performance phase change materials, including operation speed, data retention, resistance drift etc. In this work, a high performance PCRAM device based on antimony-rich RexSb3Te material was put forward and studied. Excellent data retention, fast operation speed, low resistance drift, low power consumption and good cycle characteristics were achieved. The lattice information, bonding properties and surface morphology of the films were characterized by transmission electron microscopy, Raman spectroscopy and atomic force microscopy. Density functional theory calculations show that the Re dopant is more inclined to replace Sb and forms chemical bonds with Te, and the Re-Te bonds are more stable than the previous Sb-Te bonds, which is conducive to the formation of stable precursors to accelerate nucleation. The research shows that the antimony-rich Re0.18Sb3Te material has good overall performance, which provides a strategy for developing high-performance memory.

Revolutionizing Glucose Monitoring: Enzyme-Free 2D-MoS2 Nanostructures for Ultra-Sensitive Glucose Sensors with Real-Time Health-Monitoring Capabilities.

The growing requirement for real-time monitoring of health factors such as heart rate, temperature, and blood glucose levels has resulted in an increase in demand for electrochemical sensors. This study focuses on enzyme-free glucose sensors based on 2D-MoS2 nanostructures explored by simple hydrothermal route. The 2D-MoS2 nanostructures were characterized by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and XPS techniques and were immobilized at GCE to obtain MoS2-GCE interface. The fabricated interface was characterized by electrochemical impedance spectroscopy which shows less charge transfer resistance and demonstrated superior electrocatalytic properties of the modified surface. The sensing interface was applied for the detection of glucose using amperometry. The MoS2-GCE-sensing interface responded effectively as a nonenzymatic glucose sensor (NEGS) over a linearity range of 0.01-0.20 μM with a very low detection limit of 22.08 ng mL-1. This study demonstrates an easy method for developing a MoS2-GCE interface, providing a potential option for the construction of flexible and disposable nonenzymatic glucose sensors (NEGS). Moreover, the fabricated MoS2-GCE electrode precisely detected glucose molecules in real blood serum and urine samples of diabetic and nondiabetic persons. These findings suggest that 2D-MoS2 nanostructured materials show considerable promise as a possible option for hyperglycemia detection and therapy. Furthermore, the development of NEGS might create new prospects in the glucometer industry.

Vanadium Metal Doping of Monolayer MoS2 for p-Type Transistors and Fast-Speed Phototransistors.

Modulating the electrical properties of two-dimensional (2D) materials is a fundamental prerequisite for their development to advanced electronic and optoelectronic devices. Substitutional doping has been demonstrated as an effective method for tuning the band structure in monolayer 2D materials. Here, we demonstrate a facile selective-area growth of vanadium-doped molybdenum disulfide (V-doped MoS2) flakes via pre-patterned vanadium-metal-assisted chemical vapor deposition (CVD). Optical microscopy characterization revealed the presence of flake arrays. Transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were employed to identify the chemical composition and crystalline structure of as-grown flakes. Electrical measurements indicated a light p-type conduction behavior in monolayer V-doped MoS2. Furthermore, the response time of phototransistors based on V-doped MoS2 monolayers exhibited a remarkable capability of 3 ms, representing approximately 3 orders of magnitude faster response than that observed in pure MoS2 phototransistors. This work hereby provides a feasible approach to doping of 2D materials, promising a scalable pathway for the integration of these materials into emerging electronic and optoelectronic devices.

Effects of ammonia addition on the soot nanostructure and oxidation reactivity in n-heptane/toluene diffusion flames

Co-firing NH3 with conventional hydrocarbon fuels is an important approach for reducing CO2 emissions in existing combustion systems. Besides CO2, the blending of NH3 would also notably affect soot formation and its oxidation behaviors. In the present study, we focus on the effects of NH3 on the nanostructure and oxidation characteristics of soot produced in diffusion flames of n-heptane/toluene mixtures. Two configurations of laminar co-flow diffusion flame, including both normal and inverse diffusion flames (NDF and IDFs), were used for investigation. High-resolution transmission electron microscopy (HRTEM), Raman spectroscopy (Raman), and Thermogravimetric analysis (TGA) were employed for soot characterization. The HRTEM and Raman spectra showed that with the increase of NH3 blending ratio, the fringe length (La) and the degree of graphitization decreased while the microcrystal tortuosity (Tf) increased. The results are in consistent with TGA analysis which suggests the promoting effects of NH3 on the soot oxidation reactivity. Difference between NDF and IDF with respect to the soot nanostructure and oxidation activity were discussed. It is our hope that the present results could deepen our understanding on the effects of NH3 on soot nanostructure and oxidation behavior and benefit the design of particulate filters for combustion devices fueled with hydrocarbon/NH3 mixtures.

Superior room temperature ammonia gas sensing of copper selenide nanoflowers

Facile wet chemical synthesis was utilized to synthesize nanoflowers of copper selenide (CuSe) that exhibited exceptional room temperature ammonia (NH3) gas sensing capability. Observations of surface morphology revealed the presence of petal-like structures arranged in a flower-like pattern. The layered materials have been analyzed for their crystalline structure, phase, composition, and band gap by utilizing X-ray diffraction, Transmission Electron Microscopy, Raman spectroscopy, and energy-dispersive X-ray spectroscopy, UV-Vis, respectively. At ambient conditions, CuSe nanoflowers-based sensor demonstrated exceptional sensitivity, reaching up to 79% (200 ppm NH3) with short response and recovery time of 12.9 s and 6.3 s, respectively, at 5 ppm gas concentration. The sensor exhibited rapid response and recovery times, a broad concentration range, long-term stability over extended periods, exceptional specificity towards NH3, and good repeatability owing to its distinct flower-shaped structures assembled in thin layers. Density Functional Theory simulations were conducted to investigate the interactions between NH3 and CuSe. Our findings revealed an increase in the adsorption energy of NH3 on CuSe, indicating a stronger binding affinity. We observed a higher charge transfer from CuSe to NH3, which suggests an increase in conductivity. This increase in conductivity enhances the superior sensing capability observed in the experimental results.