Active Vibrational Modes Research Articles

Identification of optically active vibrational modes of columbite AB2O6 using the correlation method

In the modern era, the examination of molecular structure heavily relies on the application of infrared and Raman spectra within crystalline structures. These methodologies are essential in understanding the arrangement of atoms within molecules and the internal forces governing them. An essential aspect of this analysis involves identifying vibrational modes that can be detected optically. The correlation method is employed to establish rules for selecting these vibrational modes, both in crystals and molecules, through a systematic calculation process that aids in predicting their activity in Infrared (IR) and Raman spectra. The correlation method utilizes group theory to determine which vibrational modes are spectroscopically active in crystals. In our research, our aim is to employ this method to identify the irreducible representations and determine the IR and Raman active vibrational modes of orthorhombic AB2O6 compounds within the Pbcn space group. By conducting comprehensive group theory calculations, our objective is to elucidate the spectroscopic properties using the correlation method.

Opto-electronic responses of large area WSe2 layers synthesized by chemical conversion of WO3 thin films

Atomically thin tungsten diselenide (WSe2) has drawn much interest due to its remarkable optical properties and potential applications in next-generation optoelectronics and energy harvesting devices. High-quality, wafer-scale synthesis of such two-dimensional (2D) semiconductors is necessary for their practical applications. Chemical vapor deposition (CVD) is a promising method for synthesizing large-area thin films of 2D materials where the constituent elements are of widely different vapor pressure. Herein, we demonstrate large-area synthesis of the 2H phase of WSe2 with a precise control over the 2D film thickness. The first step of this process is the deposition of tungsten trioxide (WO3) films of a well-defined thickness by thermal evaporation over large areas. The subsequent selenization of these films in an atmospheric pressure CVD reactor, yields high-quality uniform films of WSe2. The quality of these films is ascertained by measuring their characteristic Raman active vibrational modes and layer thickness dependent optical absorption and photoluminescence. The photoconductivity (PC) of these films has been measured with 405, 532 and 915 nm laser excitation. We note an increase in the PC of the films with their thickness. The best photoresponsivity and detectivity obtained are 11.3 mA/W and 1.42 × 108 Jones respectively. These results are promising to create photo-transistor arrays over large areas using such WO3 processed films.

Influence of Mo doping on the structural, Raman scattering, and magnetic properties of NiO nanostructures

In this work, the Ni1-xMoxO, (x = 0.000, 0.025, 0.050, 0.075, 0.100, and 0.150) nanoparticles were prepared employing the coprecipitation method. The X-ray diffraction (XRD) confirmed that all the samples have a face-centered cubic (FCC) structure with no secondary phases by the effect of the Mo-doping. The Mo-dopants yielded smaller crystallites, reaching a size of 9 nm with x = 0.150. The transmission electron microscope (TEM) images revealed agglomerated NiO nanoparticles with nearly spherical shapes varied to elliptical-like shapes upon increasing Mo concentration. The energy dispersive X-ray (EDX) confirmed the purity of the synthesized samples. The XPS analysis confirmed the valence states of the presented elements in the samples as Ni2+, Ni3+, Mo6+, and O2− ions. The XPS detected the reduction of the nickel and oxygen vacancies, by studying the ratio of Ni2+/Ni3+ and lattice oxygen (OL) to vacant oxygen (OV) peaks. The Raman analysis demonstrated the active vibrational modes of NiO, for all the samples, along with stretching Mo = O bonds for the doped samples. The Photoluminescence (PL) spectroscopy was employed to study the near band edge and deep level emissions, giving insight to the defect levels within the band gap. The PL affirmed the decrease of the oxygen vacancies upon Mo-doping. Besides, the magnetic hysteresis measurements at room temperature revealed the superparamagnetic contribution embedded in the antiferromagnetic matrix of NiO. The magnetization was tuned by Mo doping concentration, where it affected the saturation magnetization, coercivity, and remnant magnetization. Mo dopant can modify the magnetic property of NiO nanoparticles and can be a potential candidate in biomedical field and data storage applications.Graphical

Discrimination of vibrational modes in Ni2MnGa thin films

Vibrational properties in magnetic shape memory alloys are intrinsically connected to the topologies formed due to temperature-dependent breakdown of symmetry. In this sense, herein, we apply Raman spectroscopy in the study of Ni2MnGa films prepared by sputtering on glass and gallium arsenide substrates. Different laser wavelengths probe the Raman active vibrational modes. The non-equilibrium heating mechanisms of the electronic lattice induced by excitation laser power within the thermal penetration depth are used to explain the formation of higher order vibrational modes resulting from phonon-assisted intra-band electronic excitations. The discrimination of the Raman active modes is performed based on calculations carried out within the framework of the density functional theory considering the coexistence of austenite and martensite phases as a function of temperature in films with different crystalline textures and residual stresses. More importantly, this work presents a simple way to discriminate the vibrational modes of the austenite and martensite phases in Ni2MnGa thin films that can be easily applied in the nanodevice development process.

Giant barocaloric effects in sodium hexafluorophosphate and hexafluoroarsenate

Solid-state refrigeration using barocaloric materials is environmentally friendly and highly efficient, making it a subject of global interest over the past decade. Here, we report giant barocaloric effects in sodium hexafluorophosphate (NaPF6) and sodium hexafluoroarsenate (NaAsF6) that both undergo a cubic-to-rhombohedral phase transition near room temperature. We have determined that the low-temperature phase structure of NaPF6 is a rhombohedral structure with space group R3¯ by neutron powder diffraction. There are three Raman active vibration modes in NaPF6 and NaAsF6, i.e., F2g, Eg, and A1g. The phase transition temperature varies with pressure at a rate of dTt/dP = 250 and 310 K GPa−1 for NaPF6 and NaAsF6. The pressure-induced entropy changes of NaPF6 and NaAsF6 are determined to be around 45.2 and 35.6 J kg−1 K−1, respectively. The saturation driving pressure is about 40 MPa. The pressure-dependent neutron powder diffraction suggests that the barocaloric effects are related to the pressure-induced cubic-to-rhombohedral phase transitions.

Comparative study between chemical precipitation and chemical precipitation by spraying for the recovery of nanometric hydroxyapatite

The aim of this work was to develop a new method of assisted precipitation by spraying to obtain nanometer-sized hydroxyapatite and to compare it with conventional chemical precipitation by droplets. Scanning electron microscopy showed the morphological characteristics flake-like of HAp particles synthesized by the spray method at different reaction times and the formation of HAp from the first reaction time, which is different from the droplet method. X-ray diffraction confirmed the crystal structure and size of the synthesized HAp by Rietveld refinement, showing a crystallite size of about 3.77 nm for the spray synthesis and 18 nm for the droplet synthesis. FTIR and Raman were used to analyze the active normal vibrational modes of the synthesized HAp. The results showed that in the spray system, HAp formation occurs at the beginning of the reaction, a phenomenon that was not observed in the droplet method. In particular, FTIR analysis showed the presence of phosphate and carbonate modes of HAp as early as 9 minutes, which persisted throughout the reaction. This Furthermore, dynamic light scattering measurements show that the size distribution of HAp particles synthesized using the novel spray system is between 2 and 5 μm. This shows that the distribution with the spray method is more stable than with the droplet method, which shows the presence of irregular particles with a size distribution at 3 μm. The results emphasize the effectiveness of the proposed method in producing HAp with desirable properties for various biomedical applications.

Electric field emission in GdNiO3 microflower

GdNiO3 microflowers were synthesized by hydrothermal method with unit sizes of about 2.2–3.5 μm and petal sizes of ∼75–100 nm. The X-ray diffraction pattern (XRD) and Raman spectra reveal an orthorhombic crystal structure with the space group Pbnm and various Raman active vibrational modes i.e., Ag, B1 g, B2 g associated with rare earth nickelates. The total density of states (TDOS) was calculated by density functional theory (DFT) study using a hybrid functional (HSE06) and the volume of TDOS near the Fermi level confirms the semiconducting nature of GdNiO3 with band gap ∼0.688 eV. The local bulk work function (φ) was estimated theoretically at ∼5.35 eV from DFT calculations which is one of the essential parameters for the field enhancement factor (β). Field emission current density (J) vs. applied electric field (E) divulges a low turn-on field (Eto)∼4.6 V/μm@1 μA/cm2 and a threshold field (Eth)∼5.2 V/μm@10 μA/cm2 respectively. The Fowler-Nordheim (F-N) model was introduced to calculate β ∼1637 and long-term field emission current stability was observed experimentally > 4 h at the preset values of current 2 μA and 10 μA, respectively. The easy preparedness, low turn-on field, and long-term current stability without significant decay suggest this material to be an efficient electron field emitting material in the rare-earth nickelates series.

Dependence of the Raman vibration modes on structural properties of Tm:(ScxY1-x)2O3 laser ceramics with 0 ≤ x < 1.

We report on micro-Raman spectra of several mixed laser ceramics, i.e., 5at.%Tm:(ScxY1-xO2)3 with x = 0.121, 0.252, 0.489 and 5at.%Tm:Y2O3 ceramic. The samples were fabricated by solid-state pressureless consolidation of nanopowders produced by laser ablation of solid target in air flow. In particular, we studied the influence of Sc3+ content on the active vibration modes in terms of peak positions and shifts, linewidths and shapes: these parameters are relevant for the emission bandwidth of the laser medium. A shift towards higher frequencies is measured with the increase of the Sc3+ content in all samples in particular in (Tm0.048Y0.463Sc0.489O2)3 where the main Raman peaks are placed at 395, 494, 635 cm-1 while their shifts with Tm:Y2O3 are 22.6, 25.1, 40.1 cm-1, respectively. The assignment of the vibrational spectrum was obtained by density functional theory (DFT) with the Perdew-Burke-Enzerhof (PBE) exchange-correlation functional within the harmonic approximation framework.

Structural Refinement and Optoelectrical Properties of Nd2Ru2O7 and Gd2Ru2O7 Pyrochlore Oxides for Photovoltaic Applications.

High-performance photovoltaic devices require active photoanodes with superior optoelectric properties. In this study, we synthesized neodymium ruthenate, Nd2Ru2O7 (NRO), and gadolinium ruthenate pyrochlore oxides, Gd2Ru2O7 (GRO), via the solid-state reaction technique, showcasing their potential as promising candidates for photoanode absorbers to enhance the efficiency of dye-sensitized solar cells. A structural analysis revealed predominantly cubic symmetry phases for both materials within the Fd-3m space group, along with residual orthorhombic symmetry phases (Nd3RuO7 and Gd3RuO7, respectively) refined in the Pnma space group. Raman spectroscopy further confirmed these phases, identifying distinct active modes of vibration in the predominant pyrochlore oxides. Additionally, a scanning electron microscopy (SEM) analysis coupled with energy-dispersive X-ray spectroscopy (EDX) elucidated the morphology and chemical composition of the compounds. The average grain size was determined to be approximately 0.5 µm for GRO and 1 µm for NRO. Electrical characterization via I-V measurements revealed that these pyrochlore oxides exhibit n-type semiconductor behavior, with conductivity estimated at 1.5 (Ohm·cm)-1 for GRO and 4.5 (Ohm·cm)-1 for NRO. Collectively, these findings position these metallic oxides as promising absorber materials for solar panels.

Spectroscopic Characterization of Thermal Methane Activation by Lewis-Acid-Base Pair in a Gas-Phase Metal Nitride Anion Ta2N3.

Activation and transformation of methane is one of the "holy grails" in catalysis. Understanding the nature of active sites and mechanistic details via spectroscopic characterization of the reactive sites and key intermediates is of great challenge but crucial for the development of novel strategies for methane transformation. Herein, by employing photoelectron velocity-map imaging (PEVMI) spectroscopy in conjunction with quantum chemistry calculations, the Lewis acid-base pair (LABP) of [Taδ+-Nδ-] unit in Ta2N3 - acting as an active center to accomplish the heterolytic cleavage of C-H bond in CH4 has been confirmed by direct characterization of the reactant ion Ta2N3 - and the CH4-adduct intermediate Ta2N3CH4 -. Two active vibrational modes for the reactant (Ta2N3 -) and four active vibrational modes for the intermediate (Ta2N3CH4 -) were observed from the vibrationally resolved PEVMI spectra, which unequivocally determined the structure of Ta2N3 - and Ta2N3CH4 -. Upon heating, the LABP intermediate (Ta2N3CH4 -) containing the NH and Ta-CH3 unit can undergo the processes of C-N coupling and dehydrogenation to form the product with an adsorbed HCN molecule.

Calculating high-pressure vibrational frequencies analytically with the extended hydrostatic compression force field approach.

We report the implementation of the analytical Hessian for the mechanochemical extended hydrostatic compression force field method in the Q-Chem program package. To verify the implementation, the analytical Hessian was compared with finite difference calculations. In addition, we calculated the pressure dependency of the Raman active vibrational modes of methane, ethane, and hydrogen, as well as all IR and Raman active modes of Buckminsterfullerene, and compared the results with experimental and theoretical data. Our implementation paves the way for the analysis of geometric points on a pressure-deformed potential energy surface and provides a straightforward model to calculate the vibrational properties of molecules under high pressure.

Investigations on physical properties of (Sm, Ni) co-doped LaFeO3 perovskite

Nano crystalline samples of LaFeO3 (LFO) and La0.9Sm0.1Fe0.9Ni0.1O3 have been successfully synthesized through the sol-gel process. X-ray diffraction patterns confirm the orthorhombic phase of standard LaFeO3. FTIR spectroscopy shows the existence of two active vibrational modes around 410 and 550 cm−1. Specific heat capacity (Cp) displays exothermic and endothermic peaks, related to evaporation of water vapor and phase transitions respectively. The Cp is seen to rise in the doped sample, which ensures its increased thermal stability. Magnetic studies reveal the increase in magnetization and the transition from antiferromagnetic to ferromagnetic state in doped sample. Magnetoelectric study confirmed the multiferroic nature of LFO.

Silver and nickel modified cobalt-zinc nanostructured ferrites for potential applications

In this analysis, silver and nickel modified cobalt-zinc nanostructured ferrites, with chemical compositions of Co0.5Zn0.5AgxNiyFe2-x-yO4 (x = 0.0, 0.01, 0.02, 0.03; y = 0.0, 0.02, 0.03, 0.04) were prepared employing sol–gel auto-combustion (SGAC). All samples were inspected for elementary, structural, microstructural, and magnetic traits. The Fd3m space group geometry with pure spinel phase for the produced nanoferrites was shown by Rietveld’s refined X-ray diffraction patterns. Using the Scherrer formula, X-ray diffraction indicated that samples attain a crystallite size (t) of 38-63 (± 0.01) nm. The field emission scanning electron microscopy revealed that grain growth was not uniform but rather agglomerated, of varying shapes and sizes. The vibrational stretching within the metal-oxygen at interstitial sites was confirmed by Fourier-transform infrared spectroscopy, which clearly indicates the creation of Co-Zn spinel nanoferrites. Furthermore, in all the produced samples, five active Raman vibrational modes (Eg, 3T2g, A1g) are present, and all of these are related to the cubic spinel structure. A vibrating sample magnetometer is utilized to examine the magnetic traits of produced magnetic samples, displaying soft magnetic behavior. The Co0.5Zn0.5AgxNiyFe2-x-yO4 (x = 0.00; y = 0.00) sample attains the maximum saturation magnetization (Ms = 64.94 (± 0.001) emu g−1), whereas the maximum coercivity (Hc = 217.33 ± 0.001 Oe) was attained by the Co0.5Zn0.5AgxNiyFe2-x-yO4 (x = 0.03; y = 0.04) sample, respectively. Therefore, due to the magnetic softness and excellent values of magnetic parameters of the integrated samples, it is possible to use them for potential applications such as recording media, switching, multi-layer chip indicators (MLCIs), and power applications.

Tailored auto-combustion synthesis and optical and structural characterization of TiO2:Dy3+(1–11 mol%) nanostructures for wLED and latent finger print applications

Un-doped and dysprosium (Dy3+) doped (1–11 mol%) titanium dioxide (TiO2) nanoparticles (NPs) were synthesized by low temperature solution combustion route. The structural, morphological and nanostructural characterization of NPs were performed by powder x-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis, respectively. Rarely found rutile to anatase phase transition was observed by Dy3+ doping in TiO2 NPs using PXRD. The energy gap (Eg) of un-doped and Dy3+ doped TiO2 NPs were estimated by diffused reflectance spectra (DRS) between 2.92 and 3.07 eV. The active vibrational Raman modes of pure TiO2 were observed at 141, 446 and 608 cm−1. The mode alleged at 229 cm−1 indicates the rutile phase of TiO2 caused by second order effect. Studies of CIE and CCT confirmed that the NPs may be used in wLED applications. A rise of asymmetry ratio from 1.326 to 1.3453 with dopant concentration was observed in the photoluminescence (PL) spectra. The optimized TiO2:Dy3+ (9 mol%) nanostructures were used for the visualization of latent finger prints (LFPs) on porous and non-porous surfaces from level I to level III of ridge features.

A Comparative and Critical Analysis for In Vitro Cytotoxic Evaluation of Magneto-Crystalline Zinc Ferrite Nanoparticles Using MTT, Crystal Violet, LDH, and Apoptosis Assay.

Zinc ferrite nanoparticles (ZFO NPs) are a promising magneto-crystalline platform for nanomedicine-based cancer theranostics. ZFO NPs synthesized using co-precipitation method are characterized using different techniques. UV-visible spectroscopy exhibits absorption peaks specific for ZFO. Raman spectroscopy identifies Raman active, infrared active, and silent vibrational modes while Fourier transforms infrared spectroscopic (FTIR) spectra display IR active modes that confirm the presence of ZFO. X-ray diffraction pattern (XRD) exhibits the crystalline planes of single-phase ZFO with a face-centered cubic structure that coincides with the selected area electron diffraction pattern (SAED). The average particle size according to high-resolution transmission electron microscopy (HR-TEM) is 5.6 nm. X-ray photoelectron spectroscopy (XPS) signals confirm the chemical states of Fe, Zn, and O. A superconducting quantum interference device (SQUID) displays the magnetic response of ZFO NPs, showing a magnetic moment of 45.5 emu/gm at 70 kOe. These ZFO NPs were then employed for comparative cytotoxicity evaluation using MTT, crystal violet, and LDH assays on breast adenocarcinoma epithelial cell (MCF-7), triple-negative breast cancer lines (MDA-MB 231), and human embryonic kidney cell lines (HEK-293). Flow cytometric analysis of all the three cell lines were performed in various concentrations of ZFO NPs for automated cell counting and sorting based on live cells, cells entering in early or late apoptotic phase, as well as in the necrotic phase. This analysis confirmed that ZFO NPs are more cytotoxic towards triple-negative breast cancer cells (MDA-MB-231) as compared to breast adenocarcinoma cells (MCF-7) and normal cell lines (HEK-293), thus corroborating that ZFO can be exploited for cancer therapeutics.

New Density Matrix Renormalization Group Approaches for Strongly Correlated Systems Coupled with Large Environments.

Thanks to the high compression of the matrix product state (MPS) form of the wave function and the efficient site-by-site iterative sweeping optimization algorithm, the density matrix normalization group (DMRG) and its time-dependent variant (TD-DMRG) have been established as powerful computational tools in accurately simulating the electronic structure and quantum dynamics of strongly correlated molecules with a large number (101-2) of quantum degrees of freedom (active orbitals or vibrational modes). However, the quantitative characterization of the quantum many-body behaviors of realistic strongly correlated systems requires a further consideration of the interaction between the embedded active subsystem and the remaining correlated environment, e.g., a larger number (102-3) of external orbitals in electronic structure or infinite condensed-phase phononic modes in nucleus dynamics. To this end, we introduced three new post-DMRG and TD-DMRG approaches, namely (1) DMRG2sCI-MRCI and DMRG2sCI-ENPT by the reconstruction of selected configuration interaction (sCI) type of compact reference function from DMRG coefficients and the use of externally contracted MRCI (multireference configuration interaction) and Epstein-Nesbet perturbation theory (ENPT), without recourse to the expensive high order n-electron reduced density matrices (n-RDMs). (2) DMRG combined with RR-MRCI (renormalized residue-based MRCI), which improves the computational accuracy and efficiency of internally contracted (ic) MRCI by renormalizing the contracted bases with small-sized buffer environment(s) of a few external orbitals as probes based on quantum information theory. (3) HM (hierarchical mapping)-TD-DMRG in which a large environment is reduced to a small number of renormalized environmental modes (which accounts for the most vital system-environment interactions) through stepwise mapping transformation. These advances extend the efficacy of highly accurate DMRG/TD-DMRG computations to the quantitative characterization of the electronic structure and quantum dynamics in realistic strongly correlated systems coupled with large environments and are reviewed in this paper.

Impact of luminescent-ion doping on the crystallographic and photo-physical properties of the CaMoO4 nanoparticles.

Luminescent lanthanide (Ln3+ = Pr, Nd, Sm, Eu, and Tb)-ions doped calcium molybdate(CaMoO4) nanoparticles(NPs) were prepared by the polyol wet-chemical route. X-ray diffraction (XRD) pattern of all samples showed the formation of a single-phase scheelite type tetragonal structure with an average crystalline size over 21.6-33.4nm. Thermal stability was evaluated to study the surface-anchored functional groups by weight loss measurement. Fourier transform infrared (FTIR) spectra were recorded to identify the adsorbed functional groups. Aqueous dispersibility and colloidal stability were recorded with the help of the UV/visible absorption spectra. These nanocrystals formed semi-transparent colloidal solutions after being evenly disseminated in aqueous media. The doping of the luminescent ions significantly affects the crystal structure and photoluminescence (PL) properties of the CaMoO4:Ln3+ NPs. In a comparative analysis of the absorption spectra, bandgap, Raman-active modes, and luminescent properties, they were greatly influenced by altering the dopant ion due to the variation in the atomic radius of the element. The doping of smaller atomic radius Ln3+-ions distorts the unit cell, and, subsequently, bond angle/length alters the symmetry of the host crystal. The distorted crystal lattice affects the crystalline, size, lattice parameter, band gap values, Raman active vibrational modes, and luminescent efficiency. The distorted crystal structure of the host lattices facilitates the movement of the oxygen vacancies through charge transfer, resulting in efficiently suppressed emission efficiency.Graphical abstract.

Sonophotocatalytic degradation of Rhodamine B dye on MgWO4 crystals modified with AgNPs

In recent years, environmental problems caused by organic pollutants, especially industrial organic dyes, have caused severe environmental issues because they are potentially toxic and non-biodegradable carcinogens. Therefore, in this work, the magnesium tungstate (MgWO4) crystals were synthesized by the polymeric precursor method, followed by heat treatment at 900 °C for 2 h. Then, the obtained crystals were modified with silver nanoparticles (AgNPs) by the photoreduction method using silver nitrate solutions at ratios (m/m%) of 0.5%, 2%, and 4%. X-ray diffraction patterns and Rietveld refinement confirmed the presence of MgWO4 crystals with a wolframite-type monoclinic structure, emphasizing that the modification did not promote structural changes, only superficial ones. Raman and Fourier-transform infrared spectroscopies showed twenty-four active vibrational modes overall, seventeen active Raman modes, and seven IR-active modes. X-ray photoelectron spectroscopy (XPS) identified the peaks related to Mg, W, and O elements in all samples, and ascribed to Ag in the modified samples. In addition, field emission scanning electron microscopy (FE-SEM) images showed that both materials present a set of small aggregated particles with irregular shapes. Moreover, the UV–Vis absorption spectra showed a shift of the maximum band to a higher wavelength value from the modification with 2% and 4% of AgNPs with direct forbidden band energy between 3.87 and 4.00 eV. The crystals modified with 2% AgNPs present improved the catalytic properties that pristine MgWO4 crystals since they showed the best sonophotocatalytic (SPC) activity with the 92% degradation rate of Rhodamine B (RhB) dye in 240 min. Finally, we demonstrate for the first time that SPC activity in these crystals enables 74% RhB degradation even after four reuse cycles, while the radical scavengers assays indicated that holes (h) and hydroxyl (OH) radicals are the main ones responsible for the chemical reactions to RhB dye degradation.

Sulfites detection by surface-enhanced Raman spectroscopy: A feasibility study

The exhaustive control required for the correct wine production needs of many chemical analysis throughout the process. The most extended investigations for wine production control are focused on the quantification of total and free SO2. Most methods described in the literature have an adequate detection limit, but they usually lack reproducibility and require a previous sample treatment for the extraction of the SO2 from the wine-matrix. In this context, Surface-Enhanced Raman Spectroscopy (SERS) can be a promising technique for free SO2 determination without the need for any sample pre-processing. This work describes a proof of concept of a new methodology based on SERS and supported by Density Functional Theory (DFT) calculations to identify the active vibrational modes of the key molecules that contribute to the concentration of free SO2 in solution. Theoretical predictions and experimental outcomes are brought together to chemometrics to get a simple and real-time free SO2 monitoring. This general procedure could pave the way towards an implementation of a portable SERS detection module for in-field measurements.

Rational optimization of g-C3N4/Co3O4 nanocomposite for enhanced photodegradation of Rhodamine B dye under visible light

Heterogeneous catalysis is widely known as an efficient, clean, and low-cost technology to mitigate the environmental pollution of industrial effluents. This research aimed at optimizing the preparation and characterization of efficient g-C3N4/Co3O4 nanocomposite for catalytic removal of Rhodamine B (Rh B) dye. The detected XRD peaks for the prepared nano-Co3O4 are matched with the cubic crystal structure. In contrast, the broad peak at 27.3° corresponding to the graphite reflection of hkl (002) was noticeably weakened in the XRD pattern of the g-C3N4/Co3O4 composite. FTIR spectra of g-C3N4/Co3O4 nanocomposites revealed the active vibrational modes of each Co3O4 and g-C3N4 component. The microstructure study of g-C3N4 showed the strong interlayer stacking of carbon nitride nanosheets, while the surface morphology of g-C3N4/Co3O4 nanocomposite revealed a hybrid particulate system. EDS analysis indicated that the spot area of g-C3N4/Co3O4 confirmed the chemical ratios of carbon, nitrogen, cobalt, and oxygen. BET measurements of g-C3N4/Co3O4 showed a significant increase in the surface area and pore volume of single components due to the lamination of stacked g-C3N4 nanosheets by the intercalated Co3O4 nanoparticles. The prepared 30% g-C3N4/Co3O4 revealed the lowest value of Eg ~1.2 eV and the highest light absorptivity suggesting strong promotion for the photocatalytic performance under visible light. The maximum photocatalytic activity of about 87% was achieved by 30% g-C3N4/Co3O4 due to the photonic enhancement, which reduces the recombination of excited electrons. The developed nanocomposite with a g-C3N4/Co3O4 ratio of 0.3 exhibited high stability in its photocatalytic performance after four recycling times, and a slight decrease of about 7% was estimated after the 5th reuse test.