Raman Spectroscopic Study Research Articles

Biomolecules in Pleistocene fossils from tropical cave indicate fossil biofilm

Finding biomolecules in fossils is a challenging task due to their degradation over time from physical, chemical, and biological factors. The primary hypothesis for explaining the presence of biomolecules in fossilized bones tissues suggests their survival in the fossilization process. In contrast, some of these biomolecules could either derive from bacteria biofilm, thus without a direct relationship with the fossil record or could be an artifact from measurement procedures. Raman spectroscopy studies across various fossil ages and environments have detected multiple bands ranging from 1200 to 1800 cm−1 associative of organic compounds. However, the significance of these bands remains elusive. Our research aims to address this issue through a deep Raman spectroscopy investigation on Pleistocene teeth from Tayassu and Smilodon populator. These fossils were obtained from a well-preserved stratigraphic succession in Toca de Cima do Pilão cave, near the National Park of Serra da Capivara in semiarid Brazil. We propose two hypotheses to explain the presence of organic compounds related to 1200 to 1800 cm−1 Raman spectral range in fossil tissues: (i) these bands are biological signatures of preserved fossil biomolecules, or (ii) they are exogenous biological signatures associated with the bacterial biofilm formation during post-depositional processes. Our results align with the latter hypothesis, followed by biofilm degradation. However, the specific mechanisms involved in the natural biofilm degradation in fossil records remain unexplored in this study. In our case, the formation of biofilm on fossil bones is attributed to the oligotrophic conditions of the cave sediment matrix. We present a comprehensive model to elucidate the existence of biofilm on fossilized tissues, emphasizing the pivotal role of post-depositional processes, especially water action, in the cave environment. As the fossils were discovered in a cave setting, post-depositional processes significantly contribute to the formation of the biofilm matrix. Although our study provides insights into biofilm formation, further research is needed to delve into the specific mechanisms driving natural biofilm degradation in fossils.

Effect of solvothermal reaction time on adsorption and photocatalytic activity of spinel ZnFe2O4 nanoparticles

The present investigation explored the impact of solvothermal reaction time on the adsorption properties of synthesized spinel ZnFe2O4 Nanoparticles (ZF NPs) and their photocatalytic activity for the degradation of congo red (CR) dye. The structure, morphology and chemical composition is identified for the synthesized ZF NPs. The reaction times for the solvothermal synthesis of ZF NPs were investigated at time intervals of 6 hrs and 18 hrs which are denoted as ZF-6 h and ZF-18 h respectively. The XRD confirms the formation of spinel-type ZF-6 h and ZF-18 h with crystallite size of 5.50 nm and 8.36 nm for ZF-6 h and ZF-18 h respectively. The FESEM image of ZF-6 h exhibits microspheres, whereas in ZF-18 h NPs, the microspheres undergoes deformation. TEM analysis of ZF-6 h revealed that the microspheres were consists of 8–10 nm size ZF-NPs. Raman spectroscopy and XPS studies indicates, the reaction time influence the occupancy with 64 % and 32 % of inversion of Zn2+ cations from tetrahedral to octahedral sites in ZF-6 h and ZF-18 h, respectively. The surface area of mesoporous ZF-6 h and ZF-18 h are 138.29 m2/g and 128.41 m2/g respectively as confirmed using BET and BJH techniques. The CR dye adsorption capacity of 123.73 mg/g for ZF-6 h is higher compared to ZF-18 h (99.93 mg/g). The maximum dye removal efficiency evaluated for ZF-6 h NPs and ZF-18 h NPs was 87.33 % and 73.09 % respectively upon exposure of natural sunlight. The recyclability study identifies that ZF-6 h NPs remain stable for three degradation cycles. These results indicate that reaction time in solvothermal synthesis is sensitive to the morphology and physicochemical properties of ZF NPs. The enhanced performance of such ZF NPs is attributed to the synergistic effect of adsorption followed by photocatalytic (photo-Fenton) degradation of dyes.

Complementary Multisite Turnover Catalysis toward Superefficient Bifunctional Seawater Splitting at Ampere-Level Current Density.

The utilization of seawater for hydrogen production via water splitting is increasingly recognized as a promising avenue for the future. The key dilemma for seawater electrolysis is the incompatibility of superior hydrogen- and oxygen-evolving activities at ampere-scale current densities for both cathodic and anodic catalysts, thus leading to large electric power consumption of overall seawater splitting. Here, in situ construction of Fe4N/Co3N/MoO2 heterostructure arrays anchoring on metallic nickel nitride surface with multilevel collaborative catalytic interfaces and abundant multifunctional metal sites is reported, which serves as a robust bifunctional catalyst for alkaline freshwater/seawater splitting at ampere-level current density. Operando Raman and X-ray photoelectron spectroscopic studies combined with density functional theory calculations corroborate that Mo and Co/Fe sites situated on the Fe4N/Co3N/MoO2 multilevel interfaces optimize the reaction pathway and coordination environment to enhance water adsorption/dissociation, hydrogen adsorption, and oxygen-containing intermediate adsorption, thus cooperatively expediting hydrogen/oxygen evolution reactions in base. Inspiringly, this electrocatalyst can substantially ameliorate overall freshwater/seawater splitting at 1000mA cm-2 with low cell voltages of 1.65/1.69V, along with superb long-term stability at 500-1500mA cm-2 for over 200 h, outperforming nearly all the ever-reported non-noble electrocatalysts for freshwater/seawater electrolysis. This work offers a viable approach to design high-performance bifunctional catalysts for seawater splitting.

In situ surface-enhanced Raman spectroscopy study of interfacial catalytic reaction of bifunctional metal nanoparticles

In situ surface-enhanced Raman spectroscopy study of interfacial catalytic reaction of bifunctional metal nanoparticles

Raman spectroscopy study of disorder in cation sublattice of nonstoichiometric and annealed ZnSnN2

This study examines the specific characteristics of Raman scattering observed in ZnSnN2 samples produced via magnetron co-sputtering. The spectra demonstrate a high degree of similarity to the phonon density of states. This phenomenon is caused by the presence of SnZn substitutional defects, which disrupt the ideal crystal structure and generate so-called defect-induced Raman modes across the entire first Brillouin zone. An increase in the elemental content of Sn leads to a decrease in the intensity of the 230 cm⁻1 and 660 cm⁻1 peaks and to their broadening. This suggests an intensification of the disorder within the cation sublattice. Following annealing at 450 °C in a vacuum, an increase in the intensity of the peaks at 450 cm⁻1 and 560 cm⁻1, as well as the Boson peak, was observed. We attribute these changes to the increased formation of Zn–N–Sn bonds within the film structure due to the ordering of the anion (nitrogen) sublattice. However, zinc and tin atoms still occupy random positions in their sublattices, contributing to the overall increase in structural disorder.

Polyaniline/reduced graphene oxide nanocomposites for electrochemical and solar cell applications

Polyaniline nanocomposites are synthesized via in situ chemical oxidation method by reinforcing reduced graphene oxide nanoparticles of various weight percentage. Structural, optical, thermal and electrochemical studies are performed to know the significance of introducing reduced graphene oxide into polyaniline and to analyse the importance of filler weight percentage in determining various properties of the nanocomposites. X-ray diffraction peak intensity is appeared to be maximum for nanocomposite doped with 2% filler. This composite shows minimum crystallite size and maximum photoluminescence intensity. Maximum ID/IG ratio obtained for 2% filler added nanocomposite from Raman spectroscopy studies proved that the presence of more surface defects and recombination of charge carriers are the reasons for enhanced photoluminescence. Thermal stability is found to be better for a nanocomposite with 1% reduced graphene oxide and obtained a mass retention of 60% even after heating up-to 600 °C. SEM images give various shapes of nanocomposite such as nanorods, spherical nanoparticles and button shaped nanocomposites for different filler weight percentage. Carbon to oxygen ratio is observed to be decreased as the filler percentage increased from 1% to 4% in SEM-EDAX analysis. Polymer nanocomposite with 1% reinforcement possess maximum UV and visible absorption and is found to be decreased as filler concentration increased from 1 to 4%. Electrochemical analysis is performed for polyaniline and 1% reduced graphene oxide reinforced polyaniline nanocomposite. Specific capacitance of the electrode is obtained as 212 F g−1 and 609 F/g for polyaniline and nanocomposite respectively at a scan rate of 0.01 V/S. Solar cell device performance study shows that power conversion efficiency is 5.54% for 1% reduced graphene oxide nanocomposite, 4.7% for 2% reinforced, 4.16% for 3% filler and 3.61% for 4% nanocomposite.

Engineering the S-scheme heterojunction between NiFeAl - LDH and BiOCOOH nanoflower by constructing an interfacial electric field for efficient degradation of levofloxacin under visible light

The antibiotic levofloxacin (LVF), utilized across the world during the COVID-19 pandemic, presents a notable concern in environmental safety owing to its deposition in water bodies. This work reports the engineering of S-scheme heterojunction, NiFeAl LDH coupled with BiOCOOH nanoflower by constructing an interfacial electric field for efficient degradation of LVF under visible light. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis reveal the uniform decoration of NiFeAl LDH flakes over flowers like BiOCOOH and the high crystallinity is confirmed with SAED pattern distribution. The construction of an interfacial electric field was confirmed by X-ray photoelectron microscope (XPS) analysis. The X-ray diffraction (XRD), XPS, and Raman spectroscopy studies were conducted to confirm the purity and chemical bonding nature of the BiOCOOH-NiFeAl LDH nanocatalyst (NFB NCs). The band gap of materials was calculated to be 3.38 and 2.03 eV for BiOCOOH and NiFeAl LDH respectively. The NFB NCs showed remarkable performance of 95.2 % than its pristine BiOCOOH (35.4 %) and NiFeAl LDH (18 %). ESR and scavenging studies identified the major involvement of •OH, O2•- and h+ in the process. The intermediates formed during the degradation were examined by using GC–MS and a possible degradation pathway was proposed. Furthermore, the toxicity analysis using the ECOSAR program demonstrates NFB NCs safety level for extensive wastewater treatment. The stability of the NCs over six cycles and magnetic removal properties showcased their potential for large-scale wastewater treatment applications. This comprehensive study highlights the importance of LDH in advancing photocatalytic materials for environmental remediation and paves a way for manufacturing innovation.

Raman spectroscopic study of liebenbergite and Ni2SiO4 spinel at high pressure and high temperature: nickel effects on the vibration properties of olivine and spinel structures

Raman spectroscopic study of liebenbergite and Ni2SiO4 spinel at high pressure and high temperature: nickel effects on the vibration properties of olivine and spinel structures

Raman and resonance Raman spectroscopic study of red blood cells in patients diagnosed with malaria

Raman spectroscopy was used to study erythrocytes collected from patients diagnosed with malaria at the University Hospital in Kraków and from healthy volunteers. A laser line with a wavelength of 442 nm was used to induce the Raman resonance of haem, while a laser with a wavelength of 785 nm was used for the normal Raman effect. The results were analysed using Principal Component Analysis. For the 442 nm laser line, analysis of the entire spectral range (3200 cm−1 to 300 cm−1) showed satisfactory separation of Raman spectra for healthy cells from infected cells, which was significantly improved in the 1500 cm−1–1200 cm−1 spectral range. For the 785 nm laser line, some separation was observed in each range studied, but the best results were achieved over the full spectral range. Plasmodium-derived nucleic acids and phosphodiester vibrations were observed at excitation lines of 442 nm and 785 nm, respectively.

Hybrid graphene nanoflakes for electrochemical sensing with multianalyte detection capability

This work illustrates the production of highly electrochemically active graphene by liquid phase exfoliation technique for ultrasensitive electrochemical sensors. An airless high-pressure spray technique was designed to exfoliate bulk natural graphite into nm-scaled flakes (referred as HP50). Transmission electron microscopy, Raman and X-ray photoelectron spectroscopy studies reveal that the HP50 sample has a mixed structure composed of amorphous carbon and a few-layer graphene fraction with high amount of edge plane defects. The HP50 flakes are drop cast on glassy carbon electrodes to test the simultaneous and selective electrochemical detection of hydrogen peroxide, ascorbic acid, and dopamine. In cyclic voltammetry measurements, hydrogen peroxide reduces at −0.2 V vs Ag/AgCl (1 M), while ascorbic acid and dopamine oxidize at 0.1 V vs Ag/AgCl (1 M) and 0.3 V vs Ag/AgCl (1 M), respectively. Linear sweep voltammetry demonstrates high sensitivity (164, 739, and 3357 μA mM−1 cm−2) and low limit of detection (15, 1.7, and 2.1 μM) for the three analytes, respectively. Interference studies confirm a high sensitivity and selectivity towards the different chemical species. The HP50-based multianalyte sensors are also tested against different environmental and commercial samples, illustrating their viability in practical applications.

Concentration effect of zinc ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment revealed by Raman spectroscopy

Accumulation of Zn2+ ions in protein aggregates has been suggested to be a key factor in Alzheimer’s disease etiology. However, the specific influence of Zn2+ ions on the formation of amyloid fibrils or amorphous aggregates is still much debated. Herein, we conducted a combined study of Raman spectroscopy, UV–vis absorption spectroscopy and ThT fluorescence assay on the concentration effects of Zn2+ ions on amyloid fibrillation of hen egg-white lysozyme with thermal treatment. The addition of Zn2+ ions showed a negligible effect on unfolding of the protein tertiary structures and nucleation pathways on amyloid fibrillation. In contrast, a distinct concentration-dependence was observed for the influence of Zn2+ ions on the transformation of lysozyme secondary structures. At low concentration, the metal ions do not affect the populations of major secondary structures in the final state after incubation, while they at high concentration exhibit a promotion effect on the transformation from α-helix to β-sheet-like structures. These findings provide insights into the multifaceted impact of Zn2+ ions on protein aggregation, shedding light on potential therapeutic strategies for neurodegenerative diseases.

Unveiling the mass-loading effect on the electrochemical performance of Mn3O4 thin film electrodes: A combined computational and experimental study

Abstract The remarkable storage performance of manganese oxide (Mn3O4) makes it an appealing option for use as electrodes in electrochemical capacitors. However, the storage kinetics were significantly influenced by the mass loading of the electrode. Herein, we have inspected the dependency of mass loading on the storage performance of the spray pyrolyzed Mn3O4 thin film electrodes along with the correlation of structural and morphological characteristics. X-ray diffraction and Raman spectroscopic studies proven the formation of spinel Mn3O4 with a tetragonal structure. Morphological analysis revealed that all films exhibited fibrous structures with interconnected patterns at higher mass loadings. Moreover, the surface roughness and wettability of the electrode surface were influenced by variations in mass loading. Notably, thin-film electrode with a mass loading of 0.4 mg/cm2 exhibited the highest specific capacitance value of 168 F/g at 5 mV/s in a three-electrode system. Further, electrochemical impedance spectroscopic studies showed that there were noticeable changes in the capacitive behaviour of the electrode with respect to variations in mass loading. Moreover, the Dunn approach was employed to differentiate the underlying storage mechanism of the Mn3O4 electrode. Additionally, first-principles Density Functional Theory (DFT) studies were carried out in connection with the experimental study to comprehend the structure and electronic band structure of Mn3O4. This study underscores the critical importance of mass loading for enhancing the storage performance of Mn3O4 thin-film electrodes.

Interplay of Phonon Directionality and Emission Polarization in Two-Dimensional Layered Metal Halide Perovskites.

ConspectusLayered metal halide perovskites represent a natural quantum well system for charge carriers that provides rich physics, and the organic encapsulation of the inorganic metal halide layers not only increases their stability in devices but also provides an immense freedom to design their functionality. Intriguingly, these organic moieties strongly impact the optical, electrical, and mechanical properties, not only through their dielectric, elastic, and chemical properties but also because of induced mechanical distortions in the inorganic lattice. This tunability makes two-dimensional layered perovskites (2DLPs) highly attractive as light emitters. Common consensus is that exciton-phonon coupling plays an important role in radiative recombination. For bulk and some two-dimensional (2D) materials, the band edge emission broadening can be described by the classic models for polar inorganic semiconductors, while for the temperature dependence of the self-trapped exciton emission, an analysis developed for color centers has been successfully applied. For many 2DLPs these approaches do not work because of the complexity of their vibrational spectra. However, their emission is still strongly determined by phonons, and therefore, an adequate understanding of the electron-phonon coupling needs to be developed.With polarized and angle-resolved Raman spectroscopy studies on single 2DLP flakes based on different ammonium molecules as organic cations, in 2020 we revealed very rich phonon spectra in the low-frequency regime. Although the phonon bands at low frequency can generally be attributed to the vibrations of the inorganic lattice, we found very different responses by only changing the type of organic cations. In addition, the intensity of the different phonon modes depended strongly on the angle of the linearly polarized excitation beam with respect to the in-plane axes of the octahedron lattice. In 2022, we mapped this angular dependence of the phonon modes, which allowed identification of the directionality of the different lattice vibrations. By correlating the phonon spectra with the temperature-dependent emission for a set of 2DLPs that featured very different self-trapped exciton (STE) emission, we demonstrated that the exciton relaxation cannot be related to coupling with a single (longitudinal-optical) phonon band and that several phonon bands should be involved in the emission process. To gain insights into the exciton-phonon coupling effects on the band edge emission, we performed both angle-resolved polarized emission and Raman spectroscopy on single 2D lead iodide perovskite microcrystals. These experiments revealed the impact of the organic cations on the linear polarization of the emission and corroborated that multiple phonon bands should be involved in the radiative recombination process. Analysis of the temperature-dependent line width broadening of the band edge emission showed that for many systems, the behavior cannot be described by assuming the involvement of only one phonon mode in the electron-phonon coupling process. Our studies revealed a wealth of highly directional low-frequency phonons in 2DLPs from which several bands are involved in the emission process, which leads to diverse optical and vibrational properties depending on the type of organic cation in the material.

Aggregation of Albumins under Reductive Radical Stress.

The reactions of radicals with human serum albumin (HSA) under reductive stress conditions were studied using pulse radiolysis and photochemical methods. It was proved that irradiation of HSA solutions under reductive stress conditions results in the formation of stable protein aggregates. HSA aggregates induced by ionizing radiation are characterized by unique emission, different from the UV emission of non-irradiated solutions. The comparison of transient absorption spectra and the reactivity of hydrated electrons (eaq-) with amino acids or HSA suggests that electron attachment to disulfide bonds is responsible for the transient spectrum recorded in the case of albumin solutions. The reactions of eaq- and CO2•- with HSA lead to the formation of the same products. Recombination of sulfur-centered radicals plays a crucial role in the generation of HSA nanoparticles, which are stabilized by intermolecular disulfide bonds. The process of creating disulfide bridges under the influence of ionizing radiation is a promising method for the synthesis of biocompatible protein nanostructures for medical applications. Our Raman spectroscopy studies indicate strong modification of disulfide bonds and confirm the aggregation of albumins as well. Low-temperature measurements indicate the possibility of electron tunneling through the HSA protein structure to specific CyS-SCy bridges. The current study showed that the efficiency of HSA aggregation depends on two main factors: dose rate (number of pulses per unit time in the case of pulse radiolysis) and the temperature of the irradiated solution.

Exploring 1T/2H MoS2 Nano Coral Structured Active Electrodes for Enhanced Pseudocapacitive Supercapacitors: A Rigorous Evaluation and Characterization Study

This article optimizes the synthesis parameters of nano coral structured (NC-S) molybdenum disulfide (MoS2) using hydrothermal method and enhances its physiochemical properties for high-performance supercapacitors (SC). This nano coral architecture of transition metal dichalcogenides has garnered significant attention for efficient pseudocapacitive charge storage in SC. Herein, this work demonstrates the fabrication of dual phase MoS2 by tailoring the reaction time of the NC-S. Furthermore, this effect has been explained with the help of several analytical techniques. The synthesized 1T/2H MoS2 NC-S phase was affirmed by powder X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy studies. The field emission scanning electron microscope and transmission electron microscope images unveiled nano corals like morphology with numerous active sites. Impressively, the as prepared 24, 36 and 48 h MoS2 NC-S entrenched as working electrode endows the achievement with a greater specific capacitance of about 761.82, 1550.86 and 1036.28 F/g at 1 A/g of current density manifests an outstanding rate capability of 94.5, 96.5 and 95.3% capacitive retention even after 1000 cycles. Among them, the 36 h (A-36) synthesized NC-S MoS2 possess high specific energy (43.61 Wh/kg) and power (225.50 W/kg) for this application. Additionally, it demonstrates a commendable capacitive retention of 97% for the two-cell asymmetric setup, even after 5000 cycles at 10 A/g of current density. This inventive configuration of a two-cell device is employed using a Swagelok setup, where the 1T/2H phase MoS2 NC-S//AC exhibit outstanding storage stability and sustained up to 180 sec. The promising results validate that this material can significantly enhance performance in energy storage applications.

Improved ammonia gas adsorption of surface engineered WS2 nanoflakes

Recent investigations into nanostructured WS2 have shown promising results in the detection of reducing gases, such as ammonia. However, this material faces limitations with respect to the vital parameters such as sensitivity, recovery, and repeatability over an extended period in its purest form. To address these challenges, a low-energy (5 keV) argon ion beam was used to irradiate nanostructured WS2 nanoflakes at various fluences, leading to observable morphological and structural changes. The irradiation of WS2 resulted in a significant enhancement in its ability to detect ammonia gas. The sensing response saw a threefold increase, and both the response and recovery times were reduced significantly compared to pristine samples. Ion beam irradiation changes the overall morphology of nanoflakes and induces a certain degree of defects as apparent from electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy studies. The ion-solid interaction simulation predicts a larger amount of sulfur vacancy than tungsten due to irradiation, which is also supported by experimental results. Density functional theory predicts that sulfur vacancy leads a decisive role in better adsorption of ammonia than the pristine surface. The NH3 molecule orients towards the defective surface leading to a higher charge transfer from the NH3 molecule to the surface than the pristine surface along with a smaller adsorption height.

Comprehensive study of optical contrast, reflectance, and Raman spectroscopy of multilayer graphene

Graphene research has developed quite rapidly partially because even a monatomic layer can be visualized with a conventional optical microscope. Although optical properties of multilayer graphene such as optical contrast, reflectance (R), and Raman scattering have been well studied, they are studied independently and the thickness dependence is limited to a rather thin region. In this paper, the evolution of optical properties by thickness from monolayer to multilayer graphene up to 107 nm thick is studied comprehensively. The empirically known change of color of multilayer graphene is confirmed from the R, G and B intensities extracted from the optical images. It is also found that, as far as R for visible light is concerned, multilayer graphene is not necessarily considered as a layered material, and the refractive index for monolayer graphene is applicable even for the thickest multilayer graphene flake in this study. On the other hand, the layered structure and Raman scattering at each layer are essential to reproduce the G-band intensity of Raman scattering (I(G)). Not only the multiple reflection but also the interference of scattered Raman light should be considered for I(G) of multilayer graphene thicker than ∼30 nm.

In-Situ Raman Spectroscopy of Li+ and Na+ Storage in Anodic Nanotubes

Anodizing is a high-voltage electrochemical conversion process that forms barrier-type oxide layers or self-organized nanoporous/nanotubular structures. So far, the Al2O3-like nanopores and TiO2-like nanotubes could be successfully synthesized on many valve metals and alloys.Recently, it become possible to form nanotubular structures on iron and consequently control the ratio of hematite (Fe2O3) to magnetite (Fe3O4) by subsequent thermal treatment.1 Electrochemically active nanotubes, such as self-organized TiO2 are of high interest in the battery field due to a unique one-dimensional (1D) geometry offering high volume expansion tolerance and applications without binders and conductive additives. Herein, we report an in - situ Raman spectroscopy study under current control for a better fundamental understanding of Li+/Na+ storage in nanotubes and correlate the structural fingerprints with the electrochemical data on differential capacity plots of d(Q–Q 0) dE –1.2 Real-time measurements revealed that the nanotubes had undergone two major phase transformations with increasing lithium content, disclosing the sequential steps of a lithium intercalation type of storage. In contrast, sodium-ion insertion induced no significant crystal structure modification but instead a slight crystallinity rupture, signifying a dominant nondiffusion-limited capacitive type of storage. The insight into the charge storage in a 1D material in relation to other nanostructures such as nanoparticles3 will be discussed.1. L. Fadillah, D. Kowalski, M. Vincent, C. Zhu, S. Kitano, Y. Aoki and H. Habazaki, ACS Applied Materials & Interfaces , 2023, 15, 52563-52570.2. M. Vincent and D. Kowalski, ACS Applied Nano Materials , 2023, 6, 6528-6537.3. M. Vincent, S. S. Kumar and D. Kowalski, Electrochimica Acta , 2023, 469, 143161. Figure 1

Evidence of spin-phonon interactions in MgCu2O3: low temperature Raman studies

Experimental low temperature Raman spectroscopy studies upto the temperature of 83 K were performed on MgCu2O3 compound using 785 nm excitation source. Experimentally obtained Raman spectra compare well with those obtained from DFPT calculations. Phonon modes show different behaviour below and above the Néel temperature ∼95 K. Anharmonic contribution is prominent above the Néel temperature but a significant departure from the anharmonic behaviour was observed for certain Ag and B3g modes below the Néel temperature. This behaviour is attributed to spin-phonon coupling present in the compound. The spin-phonon coupling arises due to modulation in the exchange integral by the lattice vibrations. The atomic vibrations of each mode and their effect on the exchange integral are discussed.

Study of temperature-dependent copper iodide thin film by thermal evaporation system

The development of heterostructure devices has gained significant attention towards scientific communities in the present time. This article reports on the effective use of the horizontal thermal evaporation (TE) method to successfully fabricate copper iodide (CuI) films on silicon (Si) substrates. By using the TE technique, CuI-based heterojunctions have been fabricated in this research . CuI exhibits semiconductor qualities of the p-type, making it a promising option for optoelectronic devices in the future. The temperature was varied from room temperature (RT) to 230 °C to synthesise the CuI/Si heterojunction. The structural, morphological, optical, and electrical analyses have been carried out with various substrate temperatures. The x-ray diffraction (XRD) data shows that the CuI films have demonstrated a polycrystalline character and have lattice parameters of 6.03 Å. The Raman spectroscopy study shows the microstructural analysis of CuI films. The field emission scanning electron microscopy (FESEM) study reveals the variation of grain size and shape with synthesis temperature. The atomic force microscope (AFM) was used to estimate the surface roughness. The CuI films were found to be p-type by the Hall effect measurement. The sample synthesised at 130 °C shows the highest mobility of 83.12 cm2 V−1 s−1 with a carrier concentration of 1019 cm−3. The UV-visible (UV–vis) spectroscopy measurements show good absorption of UV light by the CuI thin films. The CuI/Si heterojunctions are rectifying, as demonstrated by the I-V measurements, and those respond well to UV light irradiation.