UV-vis Absorption Spectroscopy Research Articles

A comparative study of the biosynthesis of CuNPs by Niallia circulans G9 and Paenibacillus sp. S4c strains: characterization and application as antimicrobial agents

BackgroundBiosynthesis of metallic nanoparticles using microorganisms are a fabulous and emerging eco-friendly science with well-defined sizes, shapes and controlled monodispersity. Copper nanoparticles, among other metal particles, have sparked increased attention due to their applications in electronics, optics, catalysis, and antimicrobial agents.ResultsThis investigation explains the biosynthesis and characterization of copper nanoparticles from soil strains, Niallia circulans G9 and Paenibacillus sp. S4c by an eco-friendly method. The maximum reduction of copper ions and maximum synthesis CuNPs was provided by these strains. Biogenic formation of CuNPs have been characterized by UV–visible absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray analysis and transmission electron microscopy analysis. Using UV-visible spectrum scanning, the synthesised CuNPs’ SPR spectra showed maximum absorption peaks at λ304&308 nm. TEM investigation of the produced CuNPs revealed the development of spherical/hexagonal nanoparticles with a size range of 13–100 nm by the G9 strain and spherical nanoparticles with a size range of 5–40 nm by the S4c strain. Functional groups and chemical composition of CuONPs were also confirmed. The antimicrobial activity of the biosynthesized CuNPs were investigated against some human pathogens. CuNPs produced from the G9 strain had the highest activity against Candida albicans ATCC 10,231 and the lowest against Pseudomonas aeruginosa ATCC 9027. CuNPs from the S4c strain demonstrated the highest activity against Escherichia coli ATCC 10,231 and the lowest activity against Klebsiella pneumonia ATCC 13,883.ConclusionThe present work focused on increasing the CuNPs production by two isolates, Niallia circulans G9 and Paenibacillus sp. S4c, which were then characterized alongside. The used analytics and chemical composition techniques validated the existence of CuONPs in the G9 and S4c biosynthesized nano cupper. CuNPs of S4c are smaller and have a more varied shape than those of G9 strain, according to TEM images. In terms of antibacterial activity, the biosynthesized CuNPs from G9 and S4c were found to be more effective against Candida albicans ATCC 10,231 and E. coli ATCC 10,231, respectively.

A joint experimental and theoretical investigation of the binding mechanism between zein and folic acid in an ethanol–water solution

ABSTRACT The aim of the present study was to determine the binding mechanisms between zein and folic acid in an ethanol – water solution. Fluorescence spectroscopy demonstrated that folic acid quenched the fluorescence intensity of zein by both dynamic and static fluorescence quenching mechanisms, with static quenching playing a prominent role. The binding constants (Ka) of the zein-folic acid complex at 292, 302, and 312 K were evaluated to be 5.97 × 105, 3.00 × 105 and 1.54 × 105 L/mol, respectively. The process of folic acid binding zein was driven by ∆H0 = –51.24 kJ/mol, ∆S0 = –64.90 J/mol•K. Van der Waals forces and hydrogen bonding primarily governed the formation of the zein-folic acid complex. Confirmation of the complex formation was obtained via UV-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and circular dichroism spectroscopy, which also revealed alterations in the secondary structure of zein upon binding to folic acid. Measurements of particle size and zeta potential demonstrated an enhancement in the stability of the complex system. Scanning electron microscopy and transmission electron microscopy showed the complex to possess a spherical morphology, with significant changes in the zein’s morphology following its binding to folic acid. Additionally, zein increased the photostability of folic acid against UV light radiation. Molecular docking and molecular dynamics simulations were used to investigate the binding mechanisms involved further, and the results effectively elucidated the observed experimental phenomena. This research establishes a significant theoretical foundation for the utilization of zein as a system for delivering and safeguarding folic acid.

Structural and optical properties of polymer blend nanocomposites based on PVP/PVA incorporated AgNO3

Abstract In this study, polymer nanocomposite based on polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and silver nitrate (AgNO3) has been prepared through chemical reduction rate and casting method for varying concentrations of AgNO3. The PVP/PVA blend consisted of 0.6 wt.% PVP and 0.4 wt.% PVA. Following that, polymer nanocomposites were prepared by incorporating different concentrations of AgNO3 (0, 10, 20, 30, 40, and 50 wt.%) into the polymer blend. The effects of different concentrations of AgNO3 on the structural and optical properties of the PVP/PVA blend were investigated using X-ray diffraction (XRD) and UV-Vis absorption spectroscopy. The XRD analysis demonstrated that increasing the concentration of AgNO3 results in a decrease in the degree of crystallinity from 53.73 in the PVP/PVA blend to 15.77 in the PVP/PVA nanocomposite containing 50 wt.% AgNO3. UV-Vis absorbance spectra were examined to determine optical properties such as the absorption coefficient, absorption edge, optical band gap, and tails of localized states. The results revealed that the increase in AgNO3 concentrations caused a reduction in the absorption edge and optical band gap, alongside an increase in Urbach energy.

Synthesis and Photophysical Properties of a Chiral Carbon Nanoring Containing Rubicene.

Herein we report the construction of an inherently chiral carbon nanoring, cyclo[7]paraphenylene-2,9-rubicene ([7]CPPRu2,9), by combining rubicene with a C-shaped synthon through the Suzuki-Miyaura coupling reaction. The structure was fully confirmed by high-resolution mass spectroscopies (HR-MS) and various NMR techniques. The photophysical properties were investigated by UV-vis absorption and fluorescence spectroscopy as well as the time-resolved fluorescence decay. Moreover, two enantiomers (M)/(P)-[7]CPPRu2,9 were successfully resolved by recyclable HPLC and studied by CD and CPL spectra.

Elucidating the Role of Electron Transfer in the Photoluminescence of MoS2 Quantum Dots Synthesized by fs-Pulse Ablation.

Herein, MoS2 quantum dots (QDs) with controlled optical, structural, and electronic properties are synthesized using the femtosecond pulsed laser ablation in liquid (fs-PLAL) technique by varying the pulse width, ablation power, and ablation time to harness the potential for next-generation optoelectronics and quantum technology. Furthermore, this work elucidates key aspects of the mechanisms underlying the near-UV and blue emissions the accompanying large Stokes shift, and the consequent change in sample color with laser exposure parameters pertaining to MoS2 QDs. Through spectroscopic analysis, including UV-visible absorption, photoluminescence, and Raman spectroscopy, we successfully unraveled the mechanisms for the change in optoelectronic properties of MoS2 QDs with laser parameters. We realize that the occurrence of a secondary phase, specifically MoO3-x, is responsible for the significant Stokes shift and blue emission observed in this QD system. The primary factor influencing these activities is the electron transfer observed between these two phases, as validated by excitation-dependent photoluminescence and XPS and Raman spectroscopies.

Highly sensitive absorbance measurement using droplet microfluidics integrated with an oil extraction and long pathlength detection flow cell.

In droplet microfluidics, UV-Vis absorption spectroscopy along with colorimetric assays have been widely used for chemical and biochemical analysis. However, the sensitivity of the measurement can be limited by the short optical pathlength. Here we report a novel design to enhance the sensitivity by removing oil and converting the droplets into a single-phase aqueous flow, which can be measured within a U-shape channel with long optical pathlength. The flow cells were fabricated via 3D printing. The calibration results have demonstrated complete oil removal and effective optical pathlengths similar to the designed channel lengths (from 5 to 20mm). The flow cell was further employed in a droplet microfluidic-based phosphate sensing system. The measured phosphate levels displayed excellent consistency with data obtained from traditional UV spectroscopy analysis. This flow cell design overcomes the limitations of short optical pathlengths in droplet microfluidics and has the potential to be used for in situ and continuous monitoring.

Integration of high-entropy nanozyme and hollow In2S3 nanotube heterostructures decorated with WO3 for ultrasensitive PEC aptasensing of highly toxic mycotoxin

As a highly toxic mycotoxin, patulin threatens human and animal health. Herein, a new signal amplification strategy was designed for photoelectrochemical (PEC) analysis of patulin based on nanotube-like In2S3/WO3 heterostructures with the assistance of PtRuFeCoW high-entropy alloy nanorods (HEANRs). Specifically, the prominent photoactivity of the In2S3/WO3 was investigated by UV−vis diffuse reflectance and photoluminescence spectroscopy, coupled by elaborating the photoelectron transport mechanism in detail. Simultaneously, the excellent peroxidase-like activity of the PtRuFeCoW HEANRs was certificated mainly by UV–vis absorption spectroscopy. On such foundation, the PtRuFeCoW HEANRs modified capture DNA was cast onto the In2S3/WO3 based photoanode for catalyzing 4-chloro-1-naphthol (4-CN) oxidation to form insoluble benz-4-chloro-hexadienone (4-CD) precipitate in the presence of H2O2, ultimately weakening the PEC currents. The resulting PEC sensor exhibited a wider detection range from 0.1 pg mL−1 to 500 ng mL−1 and a lower detection limit was down to 0.063 pg mL−1 (S/N = 3). The HEANRs nanozyme assisted PEC method holds great promise for ultrasensitive detection of environmental pollutants in practice.

Synthesis, characterization and LDA+U calculations of zinc oxide nanoparticles

Zinc oxide (ZnO) was prepared by the sol-gel method as thin films deposited using spray pyrolysis. The characterization of the synthesized ZnO has been carried out using x-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and UV-Visible absorption spectroscopy. The experimental results revealed that the prepared ZnO has a wurtzite hexagonal structure with an average crystallite size of about 26.7 nm. High purity and flake-like structures were achieved as SEM and energy dispersive indicated. FTIR confirmed the prepared ZnO’s high purity as the Zn-O stretching peak was very intense. The optical parameters were comprehensively investigated, including absorption, reflection, extinction coefficient, refractive index, and optical energy gap. The wurtzite hexagonal structure of ZnO was optimized using the local-density approximation with the Hubbard correction method (LDA+U). Our experimental result for the energy gap is 3.28 (eV), which is in excellent agreement with the first principle calculations. We utilize the results from the LDA+U calculation along with our experimental outcomes to calculate the thickness of the thin film in UV-Vis spectroscopy.

Insights on the effect of process conditions on the optical properties of silver ion exchanged soda-lime silicate glass

The effects of ion exchange time and temperature on the optical properties and plasmonic response of silver ion exchanged soda-lime silicate glass were investigated using scanning electron microscopy (SEM) in energy dispersive spectrometry (EDS) configuration, m-lines spectroscopy, photoluminescence (PL) spectroscopy, and UV–visible absorption spectroscopy. SEM analyses in EDS mode provided profiles of silver oxide molar concentration. These profiles were directly correlated to the silver diffusion coefficient using an adjustment procedure. The effective indices of ion exchanged glasses measured by the standard prism coupling technique (m-lines) allowed access to refractive index distributions in ion exchange regions. These ion-exchanged glasses underwent evaluation to determine their potential suitability for use in multimode planar systems. The PL results acquired after ion exchange demonstrated that the creation of Ag0 atoms from Ag+ ions was responsible for the decline and quenching of PL intensity at ion exchange times and temperatures increase. Silver nanoparticles were generated in the samples subjected to ion exchange at 480 °C without the need for post-exchange treatments. The emergence of the surface plasmon resonance band around 427 nm in the optical absorption spectra confirmed the formation of Ag nanoparticles in annealed glasses. Estimates of the UV–visible absorption spectra indicated an average size of silver nanoparticles ranging from 1.8 to 2.4 nm.

Turn-off enzyme activity of histidine-rich peptides for the detection of lysozyme.

Anassay that integrateshistidine-rich peptides (HisRPs) with high-affinity aptamerswas developed enabling the specific and sensitive determination of the target lysozyme. The enzyme-like activity of HisRP is inhibited by its interaction with a target recognized by an aptamer. In the presence of the target, lysozyme molecules progressively assemble on the surface of HisRP in a concentration-dependent manner, resulting in the gradual suppression of enzyme-like activity. This inhibition of HisRP's enzyme-like activity can be visually observed through color changes in the reaction product or quantified using UV-visible absorption spectroscopy. Under optimal conditions, the proposed colorimetric assay for lysozyme had a detection limit as low as 1 nM and exhibited excellent selectivity against other nonspecific interferents. Furthermore, subsequent research validated the practical applicability of the developed colorimetric approach to saliva samples, indicating that the assay holds significant potential for the detection of lysozymes in samples derived from humans.

Carbon gas sensors synthesized using acacia auriculiformis tree branches to detect methanol, ethanol, acetone vapors and ammonia gas

Metal oxides and carbon are the prime candidates of gas sensor devices. For the inaugural instance, carbonaceous particulate matter was meticulously derived from the branches of Acacia auriculiformis tree indigenous to Sri Lanka to detect vapor and gas. It is worth noting that biomass derived carbon had hitherto remain unexplored in the realm of vapor and gas detection. Carbon films were fabricated via the doctor blade method. The resistivity characteristic of these carbon samples exhibited discernible variations upon exposure to methanol, ethanol, acetone vapors, and ammonia gas. Notably, the gas-sensing properties of sample derived from the central core and the outer shell of Acacia auriculiformis tree branches were independently assessed in these vapors and gas at ambient temperature. Various analytical techniques, including X-ray diffraction (XRD), UVvisible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), were judiciously employed to scrutinize the structural attribute, optical band gap, chemical composition and surface morphology of the aforementioned carbon film samples, respectively. XRD analyses unequivocally confirmed the successful formation of carbonaceous films. FTIR spectra conspicuously delineated the presence of oxygen within the carbon films. Importantly, the optical band gap of our carbon films manifested within the range characteristic of organic carbon. Furthermore, the resistance of the carbon films demonstrated a significant reduction upon adsorption of each vapor. It is noteworthy that while gas sensitivities and response times were superior for carbon derived from the central core of the Acacia tree branches, the recovery times were notably expedited for carbon synthesized from the outer shell of these branches. The zenith of gas sensitivity, an impressive 187%, was recorded in response to 1000 ppm of methanol vapor, when employing carbon sourced from the central core of the acacia tree branches.

HSA and DNA binding analysis of antiviral drug cidofovir: Spectroscopic and molecular docking techniques

This article discusses the interaction of antiviral drug cidofovir (CDV) with biomolecules (HSA and DNA) under simulated physiological conditions (pH 7.4). The binding propensity of CDV with DNA was assessed through UV–visible absorption spectroscopy, fluorescence spectroscopy, and molecular docking. The results of fluorescence spectroscopy indicated that the binding of CDV to DNA induced fluorescence quenching through a static quenching mechanism, with a binding constant of 1.03 × 103 M−1 at 293 K. The groove mode of CDV binding to with calf thymus DNA (ct-DNA) was validated using dye displacement assays. The results from molecular docking confirmed the binding mode and supported the findings obtained through spectroscopic techniques. Furthermore, the binding propensity of CDV with HSA was assessed through fluorescence spectroscopy, UV–visible absorption spectroscopy, and docking simulation. The fluorescence data indicated that CDV quenches the intrinsic fluorescence of the protein through a static quenching process, with a binding constant of 5.60 × 103 M−1 at 293 K. Meanwhile, the results of docking simulation confirmed our spectroscopic findings.

Biogenic and hydrothermal synthesis, characterization, antioxidant and anticancer activities of PdNPs using Abutilon indicum leaf extract

In this study, PdNPs are synthesized by using various concentrations of leaf extract of Abutilon indicum (AI), which acts as a reducing, capping, and stabilizing through a hydrothermal method. The synthesized AI leaf extract stabilized PdNPs (AI@PdNPs) were characterized by various analytical techniques such as UV–visible, Powder XRD, DLS, FTIR, and TEM analysis. The formation of PdNPs was primarily confirmed by UV–Vis absorption spectroscopy. The synthesized AI@ PdNPs was found to be FCC crystal structure, spherical, well dispersed, without any agglomeration. PdNPs are highly stable with an average particle size of 7 ± 4 nm by using powder XRD, DLS and TEM studies respectively. FTIR spectra supports the hypothesis that biomolecules presented in AI extract are effectively involved in the reduction, stabilization and capping of AI@ PdNPs. The AI@ PdNPs were assessed for antioxidant capacity using free radical scavenging activity by DPPH and found to be 76.02 % compared to standard ascorbic acid, which is 96.7 %. The cytotoxicity study was showed that AI@ PdNPs have shown marked cytotoxicity in MCF-7 cells with IC50 value of 157.5 μg/mL and did not show marked cytotoxicity in HEK-293 cells. The standard drug (Doxorubicin) was shown the IC50 value of 18.02 µM and 66.88 µM with a maximum inhibition up to 87.26 % and 72.48 % at the highest concentration tested at 100 µM for MCF-7 and HEK-293 cells, respectively. Therefore, AI@ PdNPs could be a potential candidate for future drug development as an anticancer agent.

Development of PVA/sodium alginate incorporated with histidine capped silver nanoparticles for food packaging application

AbstractPackaging is a growing field of interest, and the use of nanotechnology is accelerating its expansion. The study reports the fabrication of poly(vinyl alcohol) (PVA) blended sodium alginate (SA) and incorporated with different ratios of histidine‐capped silver (H‐AgNPs) nanoparticle films. Fabrication of PVA/SA/H‐AgNPs films was confirmed with the surface plasmon resonance (SPR) band denoted AgNPs presence between 400 and 420 nm measured by UV–Vis absorption spectroscopy. The characteristics of the polymeric biocomposite films were significantly altered by different ratios of AgNPs. The interaction of PVA/SA and PVA/SA with AgNPs was analyzed by using FT‐IR analysis. The degree of crystallinity was increased upon increasing the concentration of H‐AgNPs as confirmed by XRD measurements. The homogeneity of dispersion and surface morphology of samples were studied by FESEM. The addition of H‐AgNPs in the polymeric film increased the surface roughness of the polymeric film confirmed by AFM analysis. The contact angle of the PVA/SA blend matrix was observed to be 46.97°, and with the incorporation of AgNPs ranging from 3%, 5%, and 7% to the blend matrix, the contact angle of the nanocomposite films in increasing hydrophobic order was 60.53°, 83.57°, and 96.20°, respectively. The incorporation of AgNPs also demonstrates that the PVA/SA blend matrix has desirable thermal stability. The improved qualities were due to H bonding between PVA, SA, and H‐AgNPs, in which molecules contact strongly with one another. Furthermore, the PVA/SA/H‐AgNPs showed significant antibacterial activity against both Gram‐positive (G+) strains (Staphylococcus aureus) and Gram‐negative (G−) strains (Escherichia coli) bacterial infections. The findings of this research indicate that the PVA/SA/H‐AgNPs fabricated composite films considerable for applications in food packaging.

Quantitative Study on a Simple Electrochemical dsDNA-Pregabalin Biosensor; Multi-Spectroscopic, Molecular Docking and Modelling Studies

Pregabalin (PGB) is a γ-aminobutyric acid (GABA) alkylated analog prescribed to treat neuropathic pain, fibromyalgia, and postherpetic neuralgia. Using analytical, spectroscopic methods and molecular docking and molecular dynamics (MD) simulations, a detailed experimental and theoretical investigation was conducted into the binding process and interactions between PGB and double-stranded fish sperm deoxyribonucleic acid (dsDNA). It was evident from the collected experimental results that PGB binds with ds-DNA. PGB attaches to dsDNA via minor groove binding, as demonstrated by the results of electrochemical studies, UV–Vis absorption spectroscopy, and replacement study with ethidium bromide and Hoechst-32588. PGB's binding constant (Kb) with dsDNA, as determined by the Benesi-Hildebrand plot, is 2.41×104 ± 0.30 at 298K. The fluorescence investigation indicates that PGB and dsDNA have a binding stoichiometry (n) of 1.21 ± 0.09. Molecular docking simulations were used in the research to computational determination of the interactions between PGB and dsDNA. The findings demonstrated that minor groove binding was the mechanism by which PGB interacted with dsDNA. Based on the electrochemically responsive PGB-dsDNA biosensor, we developed a technique for low-concentration detection of PGB utilizing differential pulse voltammetry (DPV). The voltammetric analysis of the peak current decrease in the deoxyadenosine oxidation signals resulting from the association between PGB and dsDNA enabled a sensitive estimation of PGB in pH 4.80 acetate buffer. The deoxyguanosine oxidation signals exhibited a linear relationship between 2 and 16μM PGB. The values for the limit of detection (LOD) and limit of quantitation (LOQ) were 0.57μM and 1.91μM, respectively.

Catechin detection in tea samples based on catechin-induced conformational changes in papain

Catechin, the major ingredient in tea that affects its taste, varies based on the tea variety, climate, and extraction techniques. Although several techniques have been developed to determine catechin levels, an easy-to-use method is still lacking. Herein, the catechin levels were determined using papain for the first time. After incubating papain with catechin, the precipitate was discarded, and the remaining catechin-enzyme complex in the supernatant was determined by UV-visible absorption spectroscopy. Upon catechin binding papain’s main absorption band (at 280nm) was altered, reflecting conformation changes in their aromatic amino acids. It was supported by the kinetic measurements determined with N-α-benzoyl-arginine-p-nitroanilide (BAPNA) as a substrate. Complex formation between catechin and papain markedly affects the enzyme activity, resulting in the diminishes of the yellow-colored product observed at 410nm in a concentration-dependent manner. Under the optimum conditions, the analytical curve was linear in the concentration range 0.10 – 0.80mg/mL (r2 = 0.9893) with a detection limit of 0.44mg/mL. This developed biosensor demonstrated long-term stability (90 days) and reproducibility with a relative standard deviation below 10%. This usefulness of papain’s conformation changes was further demonstrated in the analysis of tea infusion samples, and the recoveries are in the acceptable range (79.1-81.2%).

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

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

Characteristics of the incorporation of Yb defect states in CuO:ZnO nanocomposite

Exploring magnetic order in nonferromagnetic substances, such as CuO:ZnO, becomes especially attractive when introducing defect states through nonmagnetic ion doping. In this study, we delved into the impact of Yb doping on the structural, morphological, optical, and magnetic properties of CuO:ZnO. The Yb doped CuO:ZnO was prepared with different Yb concentrations (x = 0.00–20 %) via the temperature-assisted co-precipitation method. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), UV–Vis spectroscopy, and vibrating sample magnetometer (VSM) were used to investigate the structural, morphological, optical, and magnetic properties of Yb doped CuO:ZnO nanocomposites.The incorporation of Yb in CuO:ZnO nanocomposites leads to a notable shift of the characteristic XRD peaks of CuO and ZnO to lower angles, accompanied by an increase in the lattice parameters. UV–visible absorption spectroscopy shows an overall decrease in the optical band gap energy of ZnO as the Yb defect level increases. FE-SEM studies revealed the transformation of spherical structures into agglomerated non-spherical structures upon the introduction of Yb ions into CuO:ZnO nanocomposites. According to XPS data, the predominant valences of Yb-doped CuO:ZnO nanocomposites are Zn2+, Cu2+, and Yb3+. One noteworthy observation from the XPS results is that, in comparison to the intensity of OL or Oad peaks, the intensity of OV (Oxygen vacancy) defect peak increases when the Yb impurity concentration increases. Magnetic measurements demonstrated a diamagnetic order in pure ZnO, which converts to a ferromagnetic order with the incorporation of Yb defect states. The ferromagnetic properties of the Yb-doped CuO:ZnO nanocomposite can be ascribed to the exchange interaction of Yb3+ ions with defect states (Oxygen Vacancy) in ZnO and CuO.

Study of Molecular Dimer Morphology Based on Organic Spin Centers: Nitronyl Nitroxide Radicals.

In this work, in order to investigate the short-range interactions between molecules, the spin-magnetic unit nitronyl nitroxide (NN) was introduced to synthesize self-assembly single radical molecules with hydrogen bond donors and acceptors. The structures and magnetic properties were extensively investigated and characterized by UV-Vis absorption spectroscopy, electron paramagnetic resonance (EPR), and superconducting quantum interference devices (SQUIDs). Interestingly, it was observed that the single molecules can form two different dimers (ring-closed dimer and "L"-type dimer) in different solvents, due to hydrogen bonding, when using EPR to track the molecular spin interactions. Both dimers exhibit ferromagnetic properties (for ring-closed dimer, J/kB = 0.18 K and ΔES-T = 0.0071 kcal/mol; for "L"-type dimer, the values were J/kB = 9.26 K and ΔES-T = 0.037 kcal/mol). In addition, the morphologies of the fibers formed by the two dimers were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM).

Green Synthesis and Antimicrobial Study on Jujube Seed Extract Functionalized Ag Nanoparticles

AbstractGreen synthesis of Ag nanoparticles (AgNPs) by using the plant extract is a very important strategy to gain efficient antimicrobial agents with strong antimicrobial activity and low toxicity. In this study, jujube seed extract (JSE) is utilized to green synthesis of AgNPs by both hydrothermal process and solution‐based approaches. UV–vis absorption spectroscopy and infrared spectroscopy (FTIR) spectra confirm that jujube seed extract functionalized Ag nanoparticles are formed by both approaches and jujube seed extract covered on the surface of Ag nanoparticles. Transmission electron microscopy (TEM) images indicate that the JSE‐AgNPs are spherical with the average diameter of 17.7 and 14.2 nm for the hydrothermal process and solution‐based approaches, respectively. X‐ray diffraction (XRD) results indicate that the JSE‐AgNPs prepared by both approaches have face‐centered cubic crystal structure. The antimicrobial activity test reveals that minimum inhibitory concentrations (MIC) of JSE‐AgNPs by the solution‐based method are 62.5, 125, and 62.5 µg mL−1 against Escherichia coli, Staphylococcus aureus, and Candida albicans, respectively. These results imply that the JSE‐AgNPs have potential to be developed as efficient antimicrobial agents.