Raman Spectroscopy Research Articles

Assessing the combined effects of chemical and mechanical parameters on silar-grown nanostructured ZnO thin films

In the literature, a comprehensive assessment of the combined impacts of chemical and mechanical parameters on the properties of thin films grown by SILAR is missing. In this work, ZnO film formation is investigated under variable precursor concentration, pH, withdrawal speed and number of cycles. Interestingly, the produced ZnO films displayed remarkable aspect ratio and morphological variability, ranging from the commonly obtained nanograins shape towards hexagonal nanorods, flower- like rods and nanoneedles, which to our knowledge have not yet been achieved by using single step SILAR process. More particularly, low concentration and intermediate pH and withdrawal rates were favorable for nanorods formation. In addition, increasing the withdrawal speed from 26 to 30 cm·min-1 resulted in a thinner film with improved rod uniformity and reduced crystallite size. This is the first study on the impact of substrate withdrawal speed on SILAR films. Among all studied parameters, the number of cycles was particularly useful for tuning film thickness, while preserving its target shape. In addition, the films grown under a higher number of cycles showed improved film crystallinity and rod orientation with reduced dislocation density, microstrain and bandgap energy. In our conditions, the most suitable combination of parameters required for exhibiting optimized nanorod-shaped coating are: a concentration of 0.07 M, pH of 10.5, speed of 30 cm·min-1 and 40 cycles. In this case, XRD, XPS, Raman and FTIR spectra displayed typical features of hexagonal Wurtzite structure of ZnO with no impurities within the film surface, whereas AFM measured a thickness of 1.4 μm with 243 nm surface roughness.

Generating Synthetic Raman Spectra of DMMP and 2-CEES by Mathematical Transforms and Deep Generative Models

To build an automated system detecting toxic chemicals from Raman spectra, we have to obtain sufficient data of toxic chemicals. However, it usually costs high to gather Raman spectra of toxic chemicals in diverse situations. Tackling this problem, we develop methods to generate synthetic Raman spectra of DMMP and 2-CEES without actual experiments. First, we propose certain mathematical transforms to augment few original Raman spectra. Then, we train deep generative models to generate more realistic and diverse data. Analyzing synthetic Raman spectra of toxic chemicals generated by our methods through visualization, we qualitatively verify that the data are sufficiently similar to original data and diverse. For conclusion, we obtain a synthetic dataset of DMMP and 2-CEES with the proposed algorithm.

Pressure-induced phase transition from monomers to dimers in liquid crystals

ABSTRACT The crystal structures of liquid crystals, particularly various oligomers, have garnered significant attention, laying the groundwork for developing new materials and devices. Here, we demonstrate pressure plays a crucial role in the structure of liquid crystals. High-pressure Raman and photoluminescence spectra were on 5CB (4-cyano-4’−pentylbiphenyl) liquid crystal. Upon compression, the appearance of prominent fluorescence peaks suggests a phase transition. The Raman peaks, reflecting the C–H and C≡N bonds, exhibit splitting at a pressure of 3.2 GPa, further confirming the pressure-induced phase transition. The splitting is consistent with earlier calculations on the stretching vibration of the C≡N bond for various oligomers and indicates a phase transition from monomers to dimers in 5CB liquid crystal. The opposite shifts in Raman modes under pressure, specifically the blue-shift of C–H bonds and the red-shift of C≡N bonds, indicate that pressure enhances intermolecular interactions and leads to conjugation between the electrons on the C≡N bonds and the C–H bonds, resulting in dimer formation. Our findings not only reveal a novel strategy for producing oligomers in liquid crystals through the application of high pressure but also highlight that Raman spectroscopy is a valid, non-contact method for investigating the mechanisms of oligomerization.

Chemical and thermal stability of different AgNP concentrations incorporated in 0.1% DMPT UPE resin

Purpose In response to the growing demand for a polymer with improved chemical and thermal stability in the construction sector, this study aims to thoroughly explore the characteristics of silver nanoparticles (AgNP) and their various concentrations. The primary goal is to determine the effect of these nanoparticles on the chemical and thermal stability of unsaturated polyester (UPE) resin doped with dimethyl-para-toluidine (DMPT) when exposed to high temperatures. Design/methodology/approach Silver nanoparticles were first synthesized from the chemical reaction between silver nitrate and trisodium citrate before its addition to the resin. The nanocomposites were thoroughly examined using advanced analytical methods such as Fourier transform (FTIR), Raman spectroscopy and scanning electron microscope to determine chemical stability. Thermal stability tests were carried out using thermogravimetric analysis, differential thermal analysis and derivative thermogravimetry methods; viscosity and peak exotherm were also examined. Findings The data shows that increasing nanoparticle concentration improves resin chemical stability, reduces peak exotherm duration and increases viscosity. Clearly, only 1.5% AgNP concentration outperformed neat UPE resin, while 0.5% and 1% AgNP concentrations fall short in terms of thermal stability. Originality/value The enhanced resin highlights the subtle influence of nanoparticle addition, which has a greater impact on the chemical structure of the composite rather than its thermal properties.

Liquid-Solid Triboelectric Nanogenerator-Based DNA Barcode Detection Biosensor for Species Identification.

DNA barcode detection method is widely applied for species identification, which is imperative to evaluate the effect of human economic activities on the biodiversity of ecosystem. However, the wide utilization of existing detection biosensors is limited by bulky and expensive instruments, such as Raman spectroscopy and electrochemical station. Herein, a liquid-solid triboelectric nanogenerator (TENG)-based DNA barcode detection biosensor is proposed, which consists of water flow, fluid channel, and PDMS film attached by specifically designed capture probe. Through sequentially combining capture probe, targeted DNA barcode, and signal probe with Au nanoparticles (NPs), the surface charge density of friction layer of TENG decreases under the effect of AuNPs, verified by the density functional theory (DFT) method. Consequently, the peak value of output current spike signal for targeted DNA is smaller than that for other DNA, which is the working mechanism of the present TENG-based biosensor. Such biosensor successfully recognizes Alvinocaris muricola among different types of Alvinocarididae shrimps, and its low limit detection can reach 1×10-12m. The present work provides a paradigm-shift way to develop an inexpensive and accurate technique to detect DNA barcode for species identification, and paves a novel way for the application of liquid-solid TENG.

Modulation in Spin State of Co3O4 Decorated Fe Single Atom Enables a Superior Rechargeable Zinc-Air Battery Performance.

High-performance bifunctional electrocatalyst for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is the keystone for the industrialization of rechargeable zinc-air battery (ZAB). In this work, the modulation in the spin state of Fe single atom on nitrogen doped carbon(Fe1-NC) is devised by Co3O4 (Co3O4@Fe1-NC), and a mediate spin state is recorded. Besides, the d band center of Fe is downshifted associated with the increment in eg filling revealing the weakened interaction with OH* moiety, resulting in a boosted ORR performance. The ORR kinetic current density of Co3O4@Fe1-NC is 2.0- and 5.6 times higher than Fe1-NC and commercial Pt/C, respectively. Moreover, high spin state is found for Co in Co3O4@Fe1-NC contributing to the accelerated surface reconstruction of Co3O4 witnessed by operando Raman and electrochemical impedance spectroscopies. A robust OER activity with overpotential of 352mV at 50mA cm-2 is achieved, decreased by 18 and 60mV by comparison with Co3O4@NC and IrO2. The operando Raman reveals a balanced adsorption of OH* species and its deprotonation leading to robust stability. The ZAB performance of Co3O4@Fe1-NC is 193.2mW cm-2 and maintains for 200h. Furthermore, the all-solid-state ZAB shows a promising battery performance of 163.1mW cm-2.

Oxidative stress-induced cytotoxicity of HCC2998 colon carcinoma cells by ZnO nanoparticles synthesized from Calophyllum teysmannii

The field of green synthesis, namely using plant extracts for the production of metal nanoparticles, is rapidly gaining traction. Therefore, this study investigated the process of producing zinc oxide nanoparticles (ZnO NPs) using a water-based extract derived from the stem bark of Calophyllum teysmannii. Notably, this is the first documented utilization of this particular plant source. The presence of a distinct Ultraviolet-Visible (UV-Vis) absorption peak at 372 nm provided evidence for the creation of ZnO nanoparticles. The X-ray Diffractometer (XRD) and Field Emission Scanning Electron Microscopy (FESEM) investigations indicated that the nanoparticles exhibited sizes ranging from 31.5 to 59.9 nm and had spherical morphologies. Energy Dispersive X-ray Diffractometer (EDX) analysis verified the elemental composition of the ZnO nanoparticles, whereas the Fourier Transform Infrared (FTIR) spectra showed clear peaks, demonstrating their production. The FTIR examination of the C. teysmannii extract revealed peaks at around 3370 cm− 1, indicating the presence of phenolic compounds. These chemicals are likely responsible for the reduction and stabilization of the ZnO NPs. The high-resolution X-ray Photoelectron Spectroscopy (XPS) spectra clearly revealed separate peaks corresponding to Zn 2p and O 1s, providing confirmation of the chemical states and bonding contexts. The Raman Spectroscopy analysis revealed a distinct peak at around 425 cm⁻¹, confirming the presence of the wurtzite structure. The harmful effects of ZnO nanoparticles on HCC2998 (a kind of human colon cancer) and Vero (a type of monkey kidney epithelial) cells were evaluated using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT), dichlorodihydrofluorescein diacetate (DCFH-DA), and boron-Dipyrromethene (BODIPY) assays. The cancer cells underwent cell death due to oxidative stress in a dose-dependent manner, as confirmed by microscopic and flow cytometry investigations.

Label-Free Surface-Enhanced Raman Spectroscopy Detection of Amyloid Beta on Silver Nanostructured Substrates for Alzheimer's Diagnosis.

Alzheimer's disease (AD) is a public health concern, for which an early diagnosis is essential. Biomass-derived carbon fibres with surface-decorated silver nanoparticles (Ag@CFs) have been utilized as surface enhanced raman spectroscopy (SERS) sensor platformfor the detection of the amyloid beta Aβ (25-35) for the pre-diagnosis of Alzheimer's disease. Structural and morphological characterizations confirmed the distribution of plasmonic silver nanoparticles over the surface of carbon fibres. The SERS sensor performance of Ag@CFs was evaluated using rhodamine 6G, which showed an enhancement of the order of 106 which proved the effectiveness of the developed SERS sensor towards trace level detection of analyte. A range of amyloid beta concentrations, from 100uM to 10pM, have been analyzed as a proof-of concept for this study, showcasing the efficacy of the Ag@CFs based SERS sensor to detect trace level concentrations of amyloid beta, even as low as 10 pM. This investigation is a promising development in the field of AD diagnostics since it may turn out to be a non-invasive, economical and early diagnostic tool.

Self-Powered Hydrogen Production via Laser-Coordinated NiCoPt Alloy Catalysts in an Integrated Zn-Hydrazine Battery with Hydrazine Splitting.

This study proposes a novel approach for the rapid transformation of bimetallic NiCo-oxides into trimetallic NiCoPt alloys using a pulsed laser technique in an ethanol medium in the presence of Pt salts. The electrochemical results demonstrate the exceptional dual-functional activity of the optimized NiCoPt-10 alloy, effectively catalyzing both hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR). Specifically, the NiCoPt-10 alloy presents a low overpotential of 90 mV at 10 mA·cm-2 for HER and a small working potential of 0.068 V versus the reversible hydrogen electrode (RHE) at 10 mA·cm-2 for HzOR. In situ Raman spectroscopy and theoretical calculations delivered insights into the dual-functional activity of the NiCoPt alloy. Consequently, the overall hydrazine splitting (OHzS) electrolyzer, employing a NiCoPt-10||NiCoPt-10 configuration, required only 0.295 V to deliver 10 mA·cm-2. Notably, using this dual-functional NiCoPt-10 catalyst as the cathode combined with Zn foil as the anode in a Zn-hydrazine (Zn-Hz) battery, achieved efficient hydrogen (H2) production with an energy efficiency of 97%. Furthermore, self-powered H2 production is realized by integrating the Zn-Hz battery with the OHzS electrolyzer, demonstrating its excellent potential for practical applications. Thus, this rapid synthetic strategy can aid in designing effective electrocatalysts for addressing challenges in H2 energy production.

Biochemical components of corneal stroma: a study on myopia classification based on Raman spectroscopy and deep learning methods

The study aimed to identify differences in the biochemical composition of corneal stroma lenses across varying degrees of myopia using Raman spectrum characteristics. Corneal stroma lens samples from 38 patients who underwent small incision lens extraction (SMILE) surgery, were categorized into low (n = 9, spherical power ≧ -3.00D), moderate (n = 23, spherical power < -3.00D and > -6.00D), and high myopia (n = 6, spherical power ≦-6.00D) groups. A custom-built microscopic confocal Raman system (MCRS) was used to collect Raman spectra, which were processed by smoothing, denoising, and baseline calibrating to refine raw data. Independent sample t-tests were used to analyze spectral feature peaks among sample types. Significant differences (P < 0.001) were found in multiple Raman spectral characteristic peaks (854 cm-1, 937 cm-1, 1002 cm-1, 1243 cm-1, 1448 cm-1, and 2940 cm-1) between low and high myopia samples, particularly at 2940 cm-1. Differences were also found between low and moderate, and moderate and high myopia samples, although fewer than between low and high myopia samples. The three-classification model, particularly with PLS-KNN training, exhibited superior discriminative performance with accuracy rates of 95%. Similarly, the two-classification model for low and high myopia achieved high accuracy with PLS-KNN (94.4%) compared to PCA-KNN (93.3%). PLS dimensionality reduction slightly outperformed PCA, enhancing classification accuracy. In addition, in both reduction methods, the KNN algorithm demonstrated the highest accuracy and performance. The optimal PLS-KNN classification model showed AUC values of 0.99, 0.98, and 1.00 for ROC curves corresponding to low, moderate, and high myopia, respectively. Classification accuracy rates were 89.7% and 96.9%, and 100% for low and high myopia, respectively. For the two-classification model, accuracy reached 94.4% with an AUC of 0.98, indicating strong performance in distinguishing between high and low myopic corneal stroma. We found significant biochemical differences such as collagen, lipids, and nucleic acids in corneal stroma lenses across varying degrees of myopia, suggesting that Raman spectroscopy holds substantial potential in elucidating the pathogenesis of myopia.

Development of TiF4-Dendrimer Complex Gel as an Anti-Demineralization Agent for Dentin: An In Vitro Study

ObjectiveThe anti-caries effects of titanium tetrafluoride (TiF4) are well-documented, but its low pH challenges clinical application. This study evaluated PEG citrate dendrimer as a carrier to enhance TiF4 stability and efficacy. MethodsPEG-citrate dendrimer and TiF4-dendrimer gel were synthesized, and their structures confirmed using Fourier Transform Infrared Spectroscopy (FTIR), Hydrogen Nuclear Magnetic Resonance (¹H NMR), and Liquid Chromatography–Mass Spectrometry (LC-MS). Thirty-six intact human teeth were prepared, randomly divided into three groups (n=12) and subjected to pH cycling with the following treatments: titanium tetrafluoride (T), dendrimer (D), and dendrimer with TiF4 (TD). Vickers microhardness and Raman spectroscopy evaluated dentin demineralization. EDS analysis measured titanium and fluoride penetration into dentin in T and TD groups and mineral content (calcium and phosphorus) in all groups compared to controls. ResultsThe T group showed the highest microhardness loss (p<0.001), followed by D and TD groups. EDS analysis revealed no significant difference in titanium and fluorine content between the surface and subsurface in TD (p=0.344), while T had more titanium on the surface (p<0.001). TD had higher subsurface calcium content than T (p=0.008). Raman spectroscopy revealed significant changes in phosphate-to-amide and carbonate-to-amide ratios before and after pH cycling in all groups (p<0.001), with no statistical differences among groups. ConclusionUsing dendrimer as a carrier for TiF4 increased pH and enhanced TiF44 ability to limit dentin demineralization and microhardness loss. Clinical RelevanceThe application of the newly-developed TiF4-dendrimer gel might be an effective approach to prevent/ limit dentin demineralization and dentin caries.

Microbial mat textures from the Neoarchaean Donimalai Formation (Sandur Schist Belt) in the Dharwar Craton of India

Microbially induced sedimentary textures are reported from the Neoarchaean Donimalai Formation (Dharwar Supergroup) of the Sandur Schist Belt in India. These occur in chert bands interlayered with banded iron formations (BIFs). The textures appear as interspersed carbonaceous specks lining flat or wavy laminae that build into a strand-like carbonaceous meshwork. Raman spectroscopy indicates the presence of organic carbon. Elemental mapping using field emission scanning electron microscopy with energy-dispersive X-ray (FE-SEM-EDAX) analyses supports a biogenic origin. The presence of syngenetic microbial mat textures in the BIFs of the Donimalai Formation suggests microbially mediated oxidation and deposition of Fe in the predominantly anoxic Neoarchaean Ocean. Yogmaya Shukla* [yogmayashukla@bsip.res.in], Mukund Sharma [sharmamukund1@rediffmail.com], Arif H. Ansari [a.h.ansari@bsip.res.in], Veeru Kant Singh [veerukantsingh@bsip.res.in], Birbal Sahni Institute of Palaeosciences, 53 University Road, Lucknow 226 007, India; Nora Noffke [nnoffke@odu.edu], Old Dominion University, Oceanography & Physics Building, Norfolk, 23529, VA, USA.

Electrochemical detection of catechol with a disposable carbon nanotube paste electrode modified with CTAB

Abstract The accurate and rapid detection of catechol which is a class of highly toxic organic phenolic compounds, is of great importance for the protection of environment and human health. In this work, a novel electrochemical sensor for catechol was constructed by modifying multi-walled carbon nanotube paste microelectrode with a cationic surfactant of cetyltrimethylammonium bromide (CTAB) through a simple and controllable adsorption method. Electrochemical experiment results show that the modified electrode has good electrocatalytic effect to the electrochemical response of catechol. The electrochemical response mechanism of the sensor to catechol were investigated through using many analytical methods, including scanning electron microscopy, energy-dispersive spectroscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, and electrochemical techniques. Under the optimal fabrication and application conditions, the response current of catechol on the sensor exhibits a good linear relationship with its concentration from 1.0 μmol/L ~ 7.0 mmol/L with a sensitivity of 1.33 nA/(μmol/L) and a low detection limit of 15 nmol/L (S/N = 3). Applying the sensor in the detection of catechol in tap water samples and urine samples, the results were satisfactory, indicating its good application prospect.

Sputter-Coated TiO2 Films as Passivation and Hole Transfer Layers for Improved Energy Conversion with Solar Fuel WO3/CuWO4 Photoanodes.

Atomic-layer-deposited (ALD) "leaky" TiO2 has gained interest as a charge-selective protection layer for semiconductor solar fuel electrodes. Here, the use of sputter-deposited TiO2 layers as hole-selective contacts for WO3/CuWO4 type-2 heterojunction water oxidation photoanodes is demonstrated for the first time. TiO2 protection layers with varying thicknesses (2 to 128 nm) were deposited by using the radio frequency (RF) magnetron sputtering technique. The resulting TiO2 films are amorphous as evidenced by Raman spectroscopy and powder X-ray diffraction (XRD). Photoelectrochemical scans and vibrating Kelvin probe photovoltage spectroscopy show that 2-8 nm TiO2 layers nearly double the photocurrent to 0.97 mA cm-2 under AM1.5 illumination (19% AQE at 350 nm), increase the surface photovoltage signal by 25%, and increase the WO3/CuWO4 effective band gap. These outcomes can be attributed to the selectivity of TiO2 for photoholes. Additionally, SPV data suggest that TiO2 overlayers suppress copper-based surface recombination defects. Reduced photocurrents and photovoltages are measured in thicker TiO2 films (16 to 128 nm) as a result of an increasing hole transfer resistance and because of light shading effects according to photoaction spectra. The TiO2 films also improve the stability of the WO3/CuWO4 photoelectrodes, allowing nearly constant O2 evolution over 3 h after an initial 20-35% loss. Overall, this work establishes RF magnetron sputtering as a useful method to install amorphous TiO2 passivation layers for improved WO3/CuWO4 solar fuel photoelectrodes. Furthermore, we show how the combination of PEC and SPV measurements provides insight into the function of the TiO2 coatings.

A Knowledge-Based Molecular Single-Source Precursor Approach to Nickel Chalcogenide Precatalysts for Electrocatalytic Water, Alcohol, and Aldehyde Oxidations.

The development and comprehensive understanding of nickel chalcogenides are critical since they constitute a class of efficient electro(pre)catalysts for the oxygen evolution reaction (OER) and value-added organic oxidations. This study introduces a knowledge-based facile approach to analogous NiE (E = S, Se, Te) phases, originating from molecular β-diketiminato [Ni2E2] complexes and their application for OER and organic oxidations. The recorded activity trends for both target reactions follow the order NiSe > NiS > NiTe. Notably, NiSe displayed efficient performance for both OER and the selective oxidation of benzyl alcohol and 5-hydroxymethylfurfural, exhibiting stability in OER for 11 days under industrially pertinent conditions. Comprehensive analysis, including quasi in situ X-ray absorption and Raman spectroscopy, in combination with several ex situ techniques, revealed a material reconstruction process under alkaline OER conditions, involving chalcogen leaching. While NiS and NiSe experienced full chalcogen leaching and reconstruction into NiIII/IV oxyhydroxide active phases with intercalated potassium ions, the transformation of NiTe is incomplete. This study highlights the structure-activity relationship of a whole series of analogous nickel chalcogenides, directly linking material activity to the availability of active sites for catalysis. Such findings hold great promise for the development of efficient electrocatalysts for a wide range of applications, impacting various industrial processes and sustainable energy solutions.

Improved photocatalytic degradation of methylene blue and rhodamine G dye under UV-radiation by rGO-MoO3

Abstract In this work, we report facile synthesis of rGO-MoO3 nanocomposites as photocatalysts via&amp;#xD;one-step hydrothermal method. Initially, the synthesized materials were characterized by&amp;#xD;different physicochemical methods to reveal the structural, morphological, optical, and other&amp;#xD;properties. The transmission electron microscopy (TEM) and Raman spectroscopy results&amp;#xD;validate the formation of rGO-MoO3 nanocomposites. The optical bandgap values of pristine&amp;#xD;MoO3 (3.47 eV) and rGO-MoO3 (3.36 eV), reveal that they can serve as ultra-violet light&amp;#xD;photocatalysts, for the decomposition of organic pollutants e.g. methylene blue (MB) and&amp;#xD;rhodamine G (RhG) dye. The rGO-MoO3 nanocomposites significantly enhanced the&amp;#xD;photodegradation efficiency as compared to MoO3, due to the interfacial interaction between&amp;#xD;the composite parts and promote the transfer of charge carriers from MoO3 to rGO, causing a&amp;#xD;reduced rate of electron-hole recombination. The highest degradation efficiency was observed&amp;#xD;for rGO-MoO3 nanocomposite {for MB (~50%) and RhG (~96%)}, whereas for MoO3 {for&amp;#xD;MB (~40%) and RhG (~43%)}. This report highlights a noteworthy impact of rGO with MoO3&amp;#xD;nanocomposites as a photocatalyst.&amp;#xD;

Effect of Pyrolysis Temperature on the Carbon Sequestration Capacity of Spent Mushroom Substrate Biochar in the Presence of Mineral Iron

The preparation of biochar typically involves the pyrolysis of waste organic biomass. Iron-rich magnetic biochar not only inherits the characteristics of high specific surface area and porous structure from biochar but also possesses significant advantages in easy separation and recovery, which has shown great application potential in various fields such as soil improvement and water resource remediation. This study aims to explore the influence of mineral iron on the carbon sequestration capability of biochar during the pyrolysis process. Experiments were conducted by using spent mushroom substrates as raw materials to prepare biochar at different temperature intervals (300 to 600 °C). The addition of exogenous iron has been found to significantly enhance the carbon retention rate (12.2–44.5%) of biochar across various pyrolysis temperatures and, notably, improves the carbon stability of biochar at 300 °C, 400 °C, and 600 °C. Through the analysis of thermogravimetric mass spectrometry (TG-MS) and X-ray photoelectron spectroscopy (XPS), we discovered that iron catalyzes the thermochemical reactions and inhibits the release of organic small molecules (C2-C5) through both physical blocking (FexOx) and chemical bonding (C=O and O-C=O). The results of Raman spectroscopy and infrared spectroscopy analyses indicate that the addition of iron significantly promotes the graphitization process of carbon and enhances the thermal stability of biochar within the temperature range of 300 to 500 °C. When exploring the retention and stability of carbon during pyrolysis, it was found that under the conditions of 600 °C and the presence of iron, the maximum carbon sequestration rate of biochar can reach 60.6%. Overall, this study highlights the critical role of iron and pyrolysis temperature in enhancing the carbon sequestration capacity of biochar.

Unveiling the Molecular Secrets: A Comprehensive Review of Raman Spectroscopy in Biological Research

Unveiling the Molecular Secrets: A Comprehensive Review of Raman Spectroscopy in Biological Research

Comment on “utilizing Raman spectroscopy for urinalysis to diagnose acute kidney injury stages in cardiac surgery patients”

Comment on “utilizing Raman spectroscopy for urinalysis to diagnose acute kidney injury stages in cardiac surgery patients”

Evolution of tunable energy bandgap and magnetic anisotropy in Mn substituted ferrimagnetic nickel-chromates

We report a detailed study on the composition (x) dependence of structural, electronic, magnetic, and optical studies of nickel chromate spinel (NiCr2O4) at various levels of Mn substitution at B sites. No significant structural distortion from cubic symmetryFd-3m was noticed for all the compositions in the range 0 ⩽x⩽ 1 of Ni(Cr1-xMnx)2O4. However, there is significant alteration in the bond angles∠B-O-B (90.51°-93.86°) and∠A-O-B (122.48°-124.90°) (both of which follow completely opposite trend with increasingx) and bond lengths A-O (1.82-1.94 Å) and B-O (2.02-2.08 Å). The corresponding lattice parameter (a) follows Vegard's law (8.32 ± 0.001 Å ⩽a⩽ 8.45 ± 0.001Å). The electronic structure determined from thex-ray photoelectron spectroscopy reveals the divalent nature of Ni (with spin-orbit splitting energy Δ ∼ 17.62 eV). While the Cr and Mn are stable with trivalent electronic states having Δ=8 and 11.7 eV, respectively. These results are in consonance with the cationic distribution (Ni)A[(Cr1-xMnx)2]BO4obtained from the Rietveld refinement analysis. Interestingly, the current series shows a direct bandgap (EG) semiconducting nature in whichEGvaries from 1.16 to 2.40 eV within the range ofx= 0.85-0. Such variation ofEG(x) is consistent with the compositional variation of the crystal structure data with anomalous change betweenx= 0.25 and 0.6. Beyond this range, theEgmode (140 cm-1) in Raman spectra arising from Mn-O octahedral decreases continuously and vanishes at higher Mn concentrations. Our analysis shows that all the investigated compounds show long-range ferrimagnetic ordering below the Néel temperature,TFNdue to the unequal magnetic moments of the cations. However, both the ordering temperatureTFNand saturation magnetization (MS) increases progressively from 73.3 K (1500 emu mol-1) to 116 K (3600 emu mol-1) with increasing the Mn content from 0 to 1, yet the maximum anisotropy (HK~4.5 kOe,K1~2.5 × 104erg cc-1) shows an opposite trend withx. Such variation is ascribed to the altered magnetic superexchange interactions between the cations located at A and B sites following the trendJBB>JAB>JAA, (JBB/kB=13.36 K).