Characteristic Absorption Bands Research Articles

Growth of surfactant-free Au-Co bimetallic atom-bomb cracker-like microstructures: A highly active morphological dependent hybrid electrocatalyst for dioxygen reduction

This paper reports the formation of atom-bomb fire cracker (ABC) like Au-Co heterostructures by attaching folic acid-capped AuNPs (FA-AuNPs) on a glassy carbon (GC) electrode followed by cobalt electrodeposition. The characteristic absorption band at 516 nm from the UV–visible spectrum confirms the AuNPs formation and their average size was ∼6 nm as evidenced from HR-TEM. The AuNPs were then assembled on a GC electrode via 1,6-hexadiamine linker followed by the electrodeposition of Co at various applied potentials and time. XPS spectra of Au-Co clearly revealed the zero valent nature of Au and Co and Co2+ in the bimetallic assembly. The SEM results exhibited the variations in the morphology of Au-Co with respect to the applied potential and time. It was found that the deposition of Co at -0.50 V for 600 s leads to the formation of ABC-like structure only at FA-AuNPs surface. The specific atom-bomb morphology of Au-Co was not obtained at bare GC and citrate-capped AuNPs surfaces, indicating the influence of FA-AuNPs. The Au-Co showed higher electrocatalytic activity towards dioxygen reduction by shifting the onset potential by 230 and 280 mV towards zero respectively than Co and AuNPs alone. The Koutecky-Levich plot confirms the four-electron transfer mechanism of oxygen reduction at Au-Co fabricated electrode.

Magnetic and magneto-optical properties of manganese-containing antimony phosphate glasses – An alternative to Faraday rotators

Glasses in system 100-x(70SbPO4–10ZnO–20PbO) xMnO, with x = 0, 10, 20 and 30 mol %, where prepared by the conventional melting-quenching method. The glasses were cut, polished and characterized by XRD, DSC, Raman, FTIR, UV–Vis and luminescence and magnetic and magneto-optical aiming application ultimate as in magneto-optical devices. These samples containing manganese exhibit magnetic response to neodymium magnets at room temperature. In addition, they feature thermal stability above 100 °C, wide transparency in the visible and near infrared region. The optical absorption spectra of the glass revealed the presence of characteristic absorption bands of Mn2+ at 410 nm attributed to 6A1(S) → 4A1, 4E (4G) transition and possible oxidation at around 550 nm assigned to 5B1g → 5B2g transition of the Mn3+ ions. Refractive indices higher than 1.8 and characteristic emission bands around 680–720 nm, assigned to 4T1(G)→6A1(S) transition, were also observed. Magnetic susceptibility measurements revealed the paramagnetic character of the Mn-containing glasses, with antiparallel spin alignment. Finally, a linear growth trend was observed for the Verdet constant along with the Mn2+ concentration and the highest value measured, for sample containing 30 mol% of MnO, was −55.1 ± 3.2 rad T−1 m−1 at 632.8 nm. This value is close to those of some families of glasses containing rare earths, being an alternative of new low-cost magneto-optical vitreous materials.

Synthesis of ZnO co-doped with Er and Co: Effect of the dopants on the structural, optical properties and yellow eosin photocatalytic response

In the present work, the sol-gel method was used to synthesize the Zn1-x-yErxCoyO system with different cations concentrations. The effect of dopant cations on the morphological, structural, and optical properties of particles, as well as their photocatalytic degradation of Yellow Eosin (YE) dye under UV irradiation, was investigated. X-ray diffraction (XRD) indicated excellent crystallinity of Wurtzite-like ZnO structures. Fourier Transform Infrared Spectroscopy showed characteristic absorption bands of ZnO. In addition, the dopant with different ions caused a decrease in the band gap energy compared to pure ZnO (3.16 eV), which is likely due to the defect levels formation. At higher Er3+ concentrations, the materials showed a slight reduction in the band gap (3.10 eV). However, for the samples with the highest Co2+ concentration, a lower band gap (3.0 eV) was observed, indicating that higher Co2+ concentrations favor the ZnO lattice distortion. In photocatalytic tests, the degradation rate of YE (∼48.7 %) was achieved using the ZEC23 sample (2 % of Er3+ and 3 % of Co2+), which is associated with the greater surface area found for this material. In a scavenger study, there was an increase in the rate of dye degradation (66.81 %) using ZEC23 when using an electron (e–) inhibitor reagent. In the presence of MetOH, a degradation rate of 44.0 % was observed, suggesting that the •OH radicals play a key role in the YE degradation.

Optimization of visible photoluminescence emission from Ni-Zn ferrite thin films

Ni-Zn ferrite films with different thicknesses were prepared by the spray method, aiming to study the relationship between the annealing effect in an oxygen rich environment and the structural, optical properties and photoluminescence emission. X-ray diffraction (XRD) analysis used with Rietveld refinement showed that all prepared samples had a single spinel phase structure. Likewise, the Fourier transform infrared (FTIR) spectra confirmed the phase formation of Ni-Zn ferrites by appearing in both of the two characteristic absorption bands which are related to the tetrahedral and octahedral sites. For annealed thin film samples of Ni-Zn ferrite, the atomic force microscope (AFM) surface morphology exhibits pinning structure on the surface in nanoscale height, whereas for un-annealed samples, there are hills and valleys cover a broad region. The different electronic transitions were estimated from the UV-visible transmission spectrum. Strong photoluminescence (PL) intensity in the visible range was observed under the excitation of UV radiation. The intensity of the PL signal was strongest at a film thickness of 750 nm then decreased for higher thicknesses. This could be interpreted by using proposed energy level structures based on the transmission spectrum of the investigated samples. The strong PL intensity introduces the samples as a direct optical detector for UV radiation.

Natural clay mineral-periwinkle activated carbon composite: Characterisation and structural insight

The intricacies of a natural clay mineral-periwinkle shell activated carbon (NM-PAC) composite were examined using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), BET surface area analysis, and Fourier Transform Infrared spectroscopy (FTIR). TEM analysis revealed irregular shaped particles with sizes of around 100 nm and relatively good distribution characteristics. Further examination with SEM supported these findings, showing a heterogeneous microstructure with activated carbon particles evenly distributed within the clay matrix. This uniform distribution was indicative of a high surface area available for adsorption. BET surface area analysis of the NM-PAC was determined to be 72.243 m2/g. FTIR analysis highlighted the presence of characteristic absorption bands related to the vibrational and rotational states of various functional groups. The broad band in the range of 3700–3000 cm-1indicated the stretching vibration of hydroxyl groups, and new bands around 1730 cm-1 , 1250 cm-1, and 1040 cm-1, suggested the presence of carbonyl, carboxyl, and phenol groups respectively. These findings provide valuable insights into the composite's structural properties and its potential for improved adsorption efficiency, particularly for the removal of polar pollutants.

Novel Chiral CsPbBr3 Metal Halide Perovskite Magic-Sized Clusters and Metal Halide Molecular Clusters with Achiral Ligands.

We have synthesized inherently chiral cesium lead halide perovskite magic-sized clusters (PMSCs) and ligand-assisted metal halide molecular clusters (MHMCs) using the achiral ligands octanoic acid (OCA) and octylamine (OCAm). UV-vis electronic absorption was used to confirm characteristic absorption bands while circular dichroism (CD) spectroscopy was utilized to determine their chiroptical activity in the 412-419 and 395-405 nm regions, respectively. In contrast, the larger sized counterpart of PMSCs, namely, perovskite quantum dots (PQDs), do not show chirality. The inherent chirality of the clusters is tentatively attributed to a twisted chiral layered structure, defect-induced chiral structure, or twisted Pb-Br octahedra.

The new role of dipyrromethene chemosensor for absorbance-ratiometic and fluorescence “turn-on” sensing Zn2+ ions in water-organic solutions and real water samples

This study presents a dipyrromethene-based sensitive and selective probe for Zn2+ ions detection in aqueous and water-organic media. The probe demonstrates absorbance-ratiometric and “off-on” fluorescent sensing for Zn2+ in a DMSO/H2O (9:1, v/v) mixture. The 3,3′,4,4′,5,5′-hexamethyl-2,2′-dipyrromethene (HL), similar to its analogs, exhibits weak fluorescence (with a quantum yield of less than 0.001). However, upon the presence of Zn2+ ions in the sensor HL solution, there is a remarkable increase (up to 200-fold) in fluorescence intensity due to the formation of a stable intramolecular chelate complex [ZnL2]. This complex formation induces a significant hyperchromic effect and a red shift (57 nm) in the characteristic absorption bands. The sensing mechanism of the probe towards Zn2+ ions was thoroughly investigated through absorbance and fluorescent titrations, molar ratio plots, 1H NMR, and DFT/TDDFT studies. The fluorescence response exhibited a strong linear relationship with Zn2+ concentration within the range of 0 to 5.7 × 10–6 mol/L. The detection limit (LOD) and limit of quantitation (LoQ) for Zn2+ were determined as 2 × 10–8 mol/L and 6.6 × 10–8 mol/L, respectively. Moreover, the probe demonstrated high selectivity for Zn2+ ions over other metal ions (Na+, Mg2+, Al3+, Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Pd2+, Cd2+, Hg2+, Pb2+). Test systems in the form of test-strips and cotton-pads were developed based on the dipyrromethene sensor for rapid “naked-eye” detection of zinc ions in water. The sensor was successfully applied for detecting Zn2+ ions in real water samples.

Investigation of the cobalt ions diffusion processes in calcium orthovanadate crystals

In this work, the high-temperature diffusion doping method was used for introduction of active cobalt ions into calcium orthovanadate Ca3(VO4)2crystals. Experimental samples were made from a nominally pure CVO single crystal obtained by the Czochralski method. The high-temperature diffusion conditions have been optimized to obtain doped crystals of optical quality during annealing in open and closed zones. Diffusion coefficients of cobalt ions (D) were calculated for various conditions: annealing time 24 - 48 hours; temperature range 1150-1300°C; diffusants - oxide compounds of calcium, cobalt and vanadium: Co3O4, Ca10Co0.5(VO4)7 and Ca3(VO4)2:2wt.%Co3O4; diffusion direction is parallel or perpendicular to the CVO crystal optical axis. The calculated values of the diffusion coefficient varied between 2.09·10-8—1.58·10-7 cm2/s. The activation energy of the diffusion process was determined to be 2.58±0.5 and 2.63±0.5 eV for the [001] and [100] directions, respectively. The maximum cobalt concentration in doped CVO crystals was 2·1020 cm–3. The absorption spectrum of diffusion-doped Ca3(VO4)2:Co samples demonstrates the presence of absorption bands characteristic for Co2+ and Co3+ ions. It was shown that the intensity ratio of the characteristic absorption bands varies depending on the crystal doping method. The optical anisotropy of the crystal increases with dopant concentration increase.

Direct time-resolved observation of surface-bound carbon dioxide radical anions on metallic nanocatalysts

Time-resolved identification of surface-bound intermediates on metallic nanocatalysts is imperative to develop an accurate understanding of the elementary steps of CO2 reduction. Direct observation on initial electron transfer to CO2 to form surface-bound CO2•− radicals is lacking due to the technical challenges. Here, we use picosecond pulse radiolysis to generate CO2•− via aqueous electron attachment and observe the stabilization processes toward well-defined nanoscale metallic sites. The time-resolved method combined with molecular simulations identifies surface-bound intermediates with characteristic transient absorption bands and distinct kinetics from nanosecond to the second timescale for three typical metallic nanocatalysts: Cu, Au, and Ni. The interfacial interactions are further investigated by varying the important factors, such as catalyst size and the presence of cation in the electrolyte. This work highlights fundamental ultrafast spectroscopy to clarify the critical initial step in the CO2 catalytic reduction mechanism.

Green synthesis of Ag and Au NPs decorated rGO nanocomposite for high impedimetric electrochemical sensor as well as enhanced antimicrobial performance against foodborne pathogens

In the present study, Allium cepa L. leaves extract mediated silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) decorated reduced graphene oxide (Ag/Au/rGO NC’s) were synthesized and demonstrated their biological and electrochemical sensing applications. Interestingly, the synthesis of AgNPs and AuNPs was achieved rapidly within 1 h and 4 h, respectively. Whereas the production of both reduced graphene oxide (rGO) and Ag/Au/rGO NC’s was achieved at 96 h. The achieved results from the UV–Vis spectrum of 432 nm for AgNPs and 550 nm of AuNPs and the shifting of the characteristic GO absorption band of 230 nm into 270 nm as well as an absence of 305 nm confirmed the rGO synthesis. In addition, HR-XRD analyses confirmed the JCPDS file No. 04–0783 and 01–1174 pertaining to Ag and Au NPs. Further, the Raman spectroscopy, FT-IR and EDS analyses confirmed the evidence of nanomaterials biosynthesis. A polydisperse, spherical shaped average size AgNPs of 1 to 30 nm, spherical and triangular shaped AuNPs with an average size of 1 to 120 nm, and silk like appearance of a thin layered graphene sheet in rGO were observed through TEM. Also, the recorded results evident the uniform decoration of Ag and Au NPs into the rGO sheet. The electrochemical properties of as-synthesized materials were studied by electrochemical impedance spectroscopic (EIS) and cyclic voltammetry (CV) techniques. Interestingly, the Ag/Au/rGO NC’s modified electrode exhibited higher electrical conductivity and good electrocatalytic properties towards the electrooxidation of nitrite in a neutral medium than other nanomaterials. Eventually, Ag/Au/rGO NC’s confirmed the enhanced antibacterial against Gram-negative bacteria and dose dependent antifungal inhibitory activities against foodborne fungal pathogens of Fusarium graminearum, Alternaria alternata, and phytopathogenic fungus of Curvularia lunata and Sclerotinia sclerotiorum at the maximum tested conc. of 2 mg/mL, compared to other nanomaterials. From the result of zebrafish embryotoxicity (ZET), the highest toxicity was observed for AgNPs at 0.19 μg/mL. But in the case of Ag/Au/rGO NC’s the reduced toxicity was observed. Hence, the achieved results concluded the Ag/Au/rGO NC’s could be suitable for development of both as biomaterials for biomedical and effective sensors for environmental applications.

Nanofibrous Polythiophene-SnO2 composite Films: A novel approach for Low-Temperature NO2 sensing

The SnO2-incorporated interconnected nanofibrous Polythiophene (Sn-INPTh) composite thin film was successfully synthesized using a simple chemical bath deposition method. The film was systematically studied for its NO2 gas sensing application. The chemical bonding, surface morphology, and optical properties were investigated using FT-IR, FE-SEM, EDAX, AFM, and UV–Visible spectroscopy. The effects of SnO2 incorporation on the physicochemical and NO2 sensing properties of the Sn-INPTh thin films were examined. The surface morphological study revealed the nanofibrous Polythiophene morphology, which remained intact after the incorporation of SnO2. The investigation of the chemical bonding nature clearly indicated the characteristic IR absorption bands of Polythiophene, along with the emergence of additional bands corresponding to the SnO2 nanoparticles. The Sn-INPTh thin film gas sensor demonstrated the highest selectivity for NO2 among the various oxidizing and reducing gases (NH3, SO2, H2S, NO2, CO, LPG) tested at a low working temperature of 40 ± 2˚C. All of the Sn-INPTh composite thin films exhibited enhanced NO2 sensing performance, with the highest sensitivity of 81.5% and the shortest response time of 22.66 s observed for the optimized Sn-INPTh composite thin films.

Enhanced production of bacterial cellulose employing banana peel as a cost-effective nutrient resource.

Bacterial cellulose (BC) is an exopolysaccharide produced by bacteria that has unusual structural features and is more refined than plant cellulose. BC has recently gained more attention in a variety of fields including biological and biomedical applications due to its excellent physiochemical properties including easy biodegradability, better water holding capacity, high tensile strength, high thermal stability, and high degree of polymerization. However, application of BC at industrial scale is still limited due to its high production cost and lesser yielding strains. The present study is an attempt to isolate and characterize a novel BC-producing bacterial strain. The bacterial strain S5 has resulted into maximum cellulose production of 4.76 ± 0.49 gL-1 (30°C, pH 7.0). The strain has been further identified as Stenotrophomonas sp. Derivation of nutritional and cultural conditions has resulted into 2.34-fold enhanced BC production (banana peel powder, peptone, tartaric acid, pH 7, 30°C). FTIR spectrum of BC revealed characteristic absorption bands which could be attributed to the O-H band, C-H stretching, C-O-C stretching band, O-H bending, and >CH2 bending, indicative of the β-1,4 glycosidic linkages of cellulose. Thermogravimetric analysis has also revealed stability of polysaccharide backbones and characteristic weight loss points. Employment of banana peel powder has appeared as a proficient low-cost source for large-scale economic production of BC for industrial applications.

Effects of metal-ion substitution on the structural, morphological, and electrochemical properties of LiFexZnyMn2−x-yO4 (x, y = 0.25 or 0.75)

The oxides LiMn2O4, LiFe0.75Zn0.25MnO4, and LiFe0.25Zn0.25Mn1.5O4, referred to as LMO, LFZMO 0.75–0.25, and LFZMO 0.25–0.25, were synthesized at 800 °C using ultrasound-assisted thermal decomposition of nitrates (UA-TDN). X-ray diffraction (XRD) analyses confirmed the spinel structure (Fd3m space group) for all materials. Raman spectroscopy validated the characteristic absorption bands of the spinel phase. Energy-dispersive spectroscopy (EDS) verified the uniform distribution of Fe, Zn, Mn, and O in all samples and proved the expected stoichiometry for the different oxides. Scanning electron microscopy (SEM) images showed irregular polyhedral agglomerates in the synthesized oxides, with grain sizes ranging from approximately 600 to 800 nm. Electrochemical characterization was performed under N2 and O2 atmospheres, revealing electron-withdrawing effects with increasing iron content in the oxide composition. LFZMO 0.75–0.25, with a higher iron content, displayed better performance than LMO and LFZMO 0.25–0.25 in terms of discharge capacity and cycling performance at various rates. The greater discharge capacity of LFZMO 0.75–0.25 (47 mA h g −1) was in line with the cyclic voltammetry findings, wherein lower energy (∆GLi+/ Li0= 55.5 kJ mol−1) for lithium insertion correlated with an increased discharge capacity. Electrochemical Impedance Spectroscopy (EIS) was employed to determine diffusion constants, providing insights into Li+ insertion kinetics in the cathodic electrode and highlighting the significant influence of Zn and Fe incorporation on the lithium manganese oxide. Our findings are intriguing as the diffusion coefficient of DLi+ in LFZMO 0.75–0.25 (2.3 ×10−12 cm2 S−1) surpasses that of LMO (8.5 ×10−14 cm2 S−1) and LFZMO 0.25–0.25 (9.4 ×10−18 cm2 S−1). This observation further elucidates the more positive formal potential for Li+ insertion in LFZMO 0.75–0.25.

Control of physical properties in BiFeO3nanoparticles via Sm3+and Co2+ion doping.

Highly crystalline BiFeO3(BFO), Bi0.97Sm0.03FeO3(Sm-BFO) and BiFe0.97Co0.03O3(Co-BFO) nanoparticles (NPs) were utilized as potential magnetic hyperthermia agents at two different frequencies in the radiofrequency (RF) range, and the effect of Sm3+and Co2+ion doping on the physical properties of the material was examined. The thermal behaviour of the as-prepared powders disclosed that the crystallization temperature of the powders is affected by the incorporation of the dopants into the BFO lattice and the Curie transition temperature is decreased upon doping. Vibrational analysis confirmed the formation of the R3c phase in all compounds through the characteristic FT-IR absorbance bands assigned to O-Fe-O bending vibration and Fe-O stretching of the octahedral FeO6group in the perovskite, as well as through Raman spectroscopy. The shift of the Raman-active phonon modes in Sm-BFO and Co-BFO NPs indicated structural distortion of the BFO lattice, which resulted in increased local polarization and enhanced visible light absorption. The aqueous dispersion of Co-BFO NPs showed the highest magnetic hyperthermia performance at 30 mT/765 kHz, entering the therapeutic temperature window for cancer treatment, whereas the heating efficiency of all samples was increased with increasing frequency from 375 to 765 kHz, making our doped nanoparticles to be suitable candidates for potential biomedical applications.

Composites of Co-Ti-Mn substituted M-type barium hexaferrite and CuO: Structural, optical, electromagnetic and X-band absorption for commercial applications

In this research, composites of M-type barium hexaferrite (BaFe12O19) substituted with Co-Ti-Mn and Copper oxide (CuO) have been prepared to mitigate electromagnetic pollution caused by cellphones (0.9–40 GHz) and 4G–5G networking technologies. X-ray diffraction (XRD), FTIR and transmission electron microscopy (TEM) were used to study structural and morphological analysis of synthesized composites. In the XRD analysis, the composite shows a pure phase of BaM hexaferrite and copper oxide, this was further confirmed by FTIR. Characteristic absorption bands of Co-Ti-Mn substituted BaM and CuO were observed at 260.9 cm−1, 265.2 cm−1 and 273.4 cm−1; these peaks suggest the formation of BaM and CuO phase. The optical and magnetic properties of synthesized samples were characterized by UV–visspectroscopy and Vibrating sample magnetometer (VSM). The UV-blue LED application is compatible with the band gap observed by UV–visspectroscopy. Hysteresis loops show that the magnetization (Ms), remnant magnetization (Mr) and coercivity (Hc) decreased with the increase of substitution (x). At room temperature, x = 0.10 (CTMC1) yields maximum values such Ms (35.84 emu/g), Mr ( 11.75 emu/g), and Hc (478.002 Oe). The complex permittivity and permeability were investigated in the X-band (8.2–12.4 GHz) using vector network analyzer (VNA). Composite with x = 0.15 (CTMC2) yielded an optimum value of reflection loss up to −35.79 dB at a matching frequency of 11.49 GHz and more than 90 % absorption bandwidth of 1.5 GHz. The results suggest that the synthesized composites have potential to be used as new generations of electromagnetic shielding materials.

Multifunctional hydrogels simultaneously featuring ultrahigh stretchability, remarkable tearing resistance, and reusable fluorescence for information encoding–decoding and smart anticounterfeiting

Fluorescent hydrogels with fluorescent dyes are widely used for anti-counterfeiting encryption. However, developing highly stretchable and remarkable tear-resistant hydrogels with reusable fluorescence for anti-counterfeiting purposes remains challenging. In this study, we fabricated and characterized double network (DN) hydrogels comprising polyvinyl alcohol-borax (PVA-borax) as the first network and poly(methacrylamide-co-polyethylene glycol-co-pyrenylmethyl acrylate) (P(MAM-co-PEGMA-co-PyMA)) as the second network with varying MAM to PEGMA ratios. SEM images showed the hydrogels had 3D porous structures. FT-IR and thermal properties analysis (DSC and TGA) indicated the presence of hydrogen bonds between PVA-borax and P(MAM-co-PEGMA-co-PyMA) without any chemical bonds. The red shift in characteristic absorption bands at 841 and 710 cm−1 further confirmed the presence of π-π* interactions between pyrene moieties. XRD analysis revealed no significant changes in crystalline phase of the hydrogels, which facilitated the formation of a 3D network due to abundant hydrogen bond presence. When the MAM to PEGMA ratio was adjusted to 9:2, the resulting hydrogels exhibited remarkable properties such as ultra-high stretchability (strain over 3300 %), excellent notch-insensitivity, and exceptional tear resistance (tearing energy over 3.25 × 105 J/m2). Importantly, the hydrogel's fluorescence intensity could be reversibly changed by alternatively adding Fe3+ and EDTA-2Na. It could be reused more than 10 times while maintaining a fluorescence intensity of around 80 %, demonstrating its reliability as a versatile hydrogel probe for Fe3+ detection with “ON-OFF-ON” fluorescence behavior. Furthermore, the hydrogels demonstrated exceptional 2D encryption and decryption capabilities, highlighting their potential applications in information storage and data security. To improve the level of anti-counterfeiting, multiple encryption approaches such as QR codes and ASCII binary codes were rationally designed. Overall, this study successfully developed a universal DN hydrogel platform with ultra-high stretchability and remarkable tear resistance, capable of rapid encoding and decoding of complex information for smart anti-counterfeiting.

Green synthesized ZnO@CuO nanocomposites using Achyranthes aspera leaves extract for dielectric applications

ZnO@CuO Nanocomposites (NCPs) were synthesized using Achyranthes aspera plant’s leaves extract with varying weight percents of 25, 50 and 75 of ZnO. The leaves extract was prepared using laboratory distilled water with the help of magnetic stirrer at a temperature of 60ᵒC. An appropriate amount of zinc nitrate and copper nitrate were then mixed in the extract. ZnO@CuO NCPs were obtained after calcination of paste at a temperature of 400ᵒC. The annealed samples were characterized using various characterization techniques such as x-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and UV–vis spectrophotometry. FESEM images showed spherical morphology for CuO and ZnO@CuO NCPs, whereas, ZnO exhibited nanocapsules like morphology. The XRD patterns and FTIR spectra of green synthesized CuO and ZnO confirmed the formation of single-phase crystalline structure with monoclinic and hexagonal lattices. The XRD patterns of ZnO@CuO NCPs exhibited both phases corresponding to CuO and ZnO. FTIR spectra indicated all characteristic absorption bands of CuO and ZnO nanoparticles, which along with XRD Patterns confirmed the formation of ZnO@CuO NCPs. The optical band gap energy was calculated through Tauc’s relation using UV-Vis absorbance data and was found in the range of 1.54–3.05 eV. Optical band gap for nanocomposites is slightly less than that of pure ZnO and CuO nanoparticles. Dielectric studies established that the nanocomposites ZnO@CuO (25 and 50 wt% of ZnO) possess higher dielectric constant (K), dielectric loss and AC conductivity. ZnO@CuO (50 wt%) exhibits maximum dielectric constant of 14.49 × 103 with moderate dielectric loss. Hence, ZnO@CuO (50 wt%) could be a potential candidate for high K value device applications like capacitors and supercapacitors.

DEVELOPMENT OF QUALITY INDICATORS OF A NEW BIOSTIMULANT FROM PARACETAMOL WASTE

Introduction. In recent years, there has been a substantial rise in the utilization of biostimulants in agricultural crop production. The authors’ exten-sive research over the years has revealed that the byproduct of bacterial degradation of paracetamol exhibits a notable stimulatory effect on various medicinal and agricultural plants from different families. It serves as an inducer for the accumulation of biologically active substances in these plants, thereby making it a promising and efficient biostimulant. The purpose of this study is to establish a comprehensive set of indicators and create a preliminary specification for the quality control of the bacte-rial degradation product of paracetamol, which serves as a new biostimulant for medicinal and agricultural plants. Material and methods. For this study, we utilized the bacterial degradation product of paracetamol, derived from a pharmaceutical substance with an expired shelf life. The product was obtained from the Laboratory of Alkanotrophic Microorganisms, Perm Federal Research Center UB RAS (Perm). We employed various methods to analyze the product, including determining the melting point through the capillary method, assessing lead, cadmium, and arsenic content using an atomic absorption spectrometer with electrothermal atomization (MGA-915M, Lumex, Russia) and the Mga software on a personal computer running the Windows®-2000/XP operating system. Additionally, we recorded the IR spectrum using a Specord M80 IR spectrometer (Carl Zeiss Industrielle Messtechnik GmbH, Germany), and the electronic spectra were obtained with a Lambda EZ 201 spectrophotometer (Perki-nElmer, USA). The quantification of phenolic hydroxyl and carboxyl groups was performed through back acid-base potentiometric titration. Results: The product of bacterial degradation of paracetamol is practically insoluble in water, ether, very slightly soluble in chloroform, slightly soluble in hexane and acetonitrile, soluble in acetone and ethyl acetate, freely soluble in methyl alcohol, 95% ethyl alcohol and dimethyl sulfoxide. The melting point ranged from 150 to 206 °C, with decomposition. The heavy metal and arsenic content in samples of the product with varying shelf life complied with the standards outlined in general pharmacopoeia monograph 1.5.3.0009.15. The IR spectrum exhibited characteristic absorption bands of func-tional groups, including C–H aromatic (3042 cm1), –OH phenolic (3425 cm1), –NH– (3200 cm1), and C= N (1609 cm1). The electronic spectra of product solutions, in the concentration range of 5·106 to 2.5·105 g/cm3, displayed absorption maxima at λ=218 and λ=318 nm. The content of phenolic hydroxyls in the product composition ranged from 4.22 to 5.16 mmol-eq/g, while carboxyl groups ranged from 1.76 to 3.05 mmol-eq/g, comparable to the quantities found in humic acids. Conclusions. We have established a comprehensive list of indicators and developed a preliminary specification for the quality control of the bacterial degradation product of paracetamol as a biostimulant for medicinal and agricultural plants.

Sustainable Collagen Composites with Graphene Oxide for Bending Resistive Sensing.

This work reports on the development of collagen films with graphene oxide nanoparticles (GO NPs), aiming toward the development of a new generation of functional sustainable sensors. For this purpose, different GO NP contents up to 3 wt % were incorporated into a collagen matrix, and morphological, thermal, mechanical and electrical properties were evaluated. Independently of the GO NP content, all films display an increase in thermal stability as a result of the increase in the structural order of collagen, as revealed by XRD analysis. Further, the inclusion of GO NPs into collagen promotes an increase in the intensity of oxygen characteristic absorption bands in FTIR spectra, due to the abundant oxygen-containing functional groups, which lead to an increase in the hydrophilic character of the surface. GO NPs also influence the mechanical properties of the composites, increasing the tensile strength from 33.2 ± 2.4 MPa (collagen) to 44.1 ± 1.0 MPa (collagen with 3 wt % GO NPs). Finally, the electrical conductivity also increases slightly with GO NP content, allowing the development of resistive bending sensors.

Design, characterization, fabrication, and performance evaluation of ferroelectric dielectric resonator antenna for high-speed wireless communication applications

The research comprehensively analyzes the structural, electrical, and electrodynamic characteristics of Ba0.7Sr0.3TiO3 nanoparticles synthesized using a sol-gel approach. The formation of a tetragonal perovskite phase and the nano-crystalline nature have been confirmed using X-ray diffraction (XRD) analysis. Fourier transform infrared (FTIR) spectroscopy has been employed to identify characteristic absorption bands correlated with the crystal lattice vibrations of Ba0.7Sr0.3TiO3. The sample’s morphology has been examined using scanning electron microscopy (SEM), revealing a relatively dense and homogeneous composition composed of small spherical particles. The electrical properties of Ba0.7Sr0.3TiO3 nanoparticles have also been investigated using a ferroelectric measurement technique. The soft electric hysteresis loop with a small coercive field value makes the sample suitable for photovoltaic applications. Finally, a compact dielectric resonator antenna (DRA) based on Ba0.7Sr0.3TiO3 nanoparticles has been designed and characterized. The designed DRA demonstrates good impedance matching, broadside radiation pattern, and high antenna gain and efficiency at the frequency band of 5.6–6.15 GHz, making it suitable for sub-6 GHz (5 G) applications.