UV-visible Range Research Articles

Periodic stacking of two dimensional Bismuth bi-layers in Bismuth stearate thin films

Investigations of single and bilayers of bismuth are one of the most thrusting areas of research in contemporary condensed matter physics and material sciences. This is because such ultrathin layers of bismuth host interesting exotic electronic properties, which are important from both fundamental science and future application perspectives. In the past, many inorganic processes for the synthesis of single and bi-layers of bismuth were reported using physical and chemical vapor deposition techniques. The ultrathin films deposited are found to interact electronically with the substrates due to their proximity to the substrate surface. We introduce a new and easy organic channel for the synthesis of the bismuth multi-bilayers in ambient conditions. Bismuth stearate multi-bilayer thin films are deposited on the hydrophobic silicon and hydrophilic glass substrates using the Langmuir-Blodgett technique. Optical absorption spectroscopy measurements in the infrared region provided information on various bond structures present in those bismuth stearate thin films. Specular x-ray reflectivity (XRR) experiments and their analysis of such thin films unambiguously show the highly periodic stacking of bismuth bilayers along the surface-normal directions within the multilayer film structure. Model-based microstructural analysis of the XRR data further shows that each bilayer of bismuth is well separated (3.5 nm) from other bismuth bilayers by hydrocarbon chains. At these separations, the electronic states of the bismuth bilayers are expected to be non-interacting with each other. The morphology of the surface obtained from field emission scanning electron microscopy supports the XRR analysis. A bandgap of 3.2 eV was obtained for such bismuth stearate thin films from the optical spectroscopy measurements in the UV-visible range. The large separations between the bismuth-bilayers and between the substrate and the bismuth bilayers are expected to minimize the electronic interactions between them.

A Novel Photopharmacological Tool: Dual-Step Luminescence for Biological Tissue Penetration of Light and the Selective Activation of Photodrugs.

Conventional pharmacology lacks spatial and temporal selectivity in terms of drug action. This leads to unwanted side effects, such as damage to healthy cells, as well as other less obvious effects, such as environmental toxicity and the acquisition of resistance to drugs, especially antibiotics, by pathogenic microorganisms. Photopharmacology, based on the selective activation of drugs by light, can contribute to alleviating this serious problem. However, many of these photodrugs are activated by light in the UV-visible spectral range, which does not propagate through biological tissues. In this article, to overcome this problem, we propose a dual-spectral conversion technique, which simultaneously makes use of up-conversion (using rare earth elements) and down-shifting (using organic materials) techniques in order to modify the spectrum of light. Near-infrared light (980 nm), which penetrates tissue fairly well, can provide a "remote control" for drug activation. Once near-IR light is inside the body, it is up-converted to the UV-visible spectral range. Subsequently, this radiation is down-shifted in order to accurately adjust to the excitation wavelengths of light which can selectively activate hypothetical and specific photodrugs. In summary, this article presents, for the first time, a "dual tunable light source" which can penetrate into the human body and deliver light of specific wavelengths; thus, it can overcome one of the main limitations of photopharmacology. It opens up promising possibilities for the moving of photodrugs from the laboratory to the clinic.

Enhanced UV Absorption By 2D MoS2 Nanoparticles

MoS2 is a promising 2D material for solar energy harvesting applications due to its size-dependent tunable bandgap and attractive magnetic, optical, and electrical properties. This study shows an easy way to deposit a 2D layer of MoS2 nanoparticles on top of AZO/Quartz, AZO/Si, and bare Si. We investigate their UV-Vis spectral responses and potential for application in optoelectronic systems. Initial results indicate modification of the absorption spectrum over the UV-Vis range with an evident increase in the higher visible and lower UV range.

Optical spectroscopy study of damage in ion-irradiated 3C-SiC epilayers on a silicon substrate

Epitaxial cubic (100) 3C-SiC films on a (100) silicon wafer were irradiated at room temperature with 2.3-MeV Si+ or 3.0-MeV Kr+ ions up to a fluence of 1 × 1016 cm−2. The evolutions of the epilayer and the substrate were followed as a function of ion fluence by using micro-Raman spectroscopy, optical absorption, and diffuse reflectance spectroscopy in the UV-visible and near infrared range. Raman spectra evidence the amorphization of SiC films at an estimated dose of about 0.1 displacement per atom (dpa) for both ion irradiations. The narrow peaks of the Raman-allowed TO and LO modes of SiC and Si are recorded in the virgin sample, together with few peaks assigned to zone-edge modes of SiC arising from the intrinsic disorder in the strained films. Those crystal phonon peaks broaden or disappear with increasing fluence. The spectra finally exhibit broad extra peaks assigned to the formation of Si–Si and C–C wrong homonuclear bonds in the local order of the amorphous phase. The optical transmission and diffuse reflectance spectra feature interference fringe patterns in the SiC film that are smoothened out with irradiation due to the matching of refractive indices of the amorphous SiC film and Si substrate. The evolution of the refractive index of SiC and optical gap of Si are deduced from those spectra. The respective roles of ballistic effects and electronic excitations in the radiation damage of both SiC and Si are discussed for those two ions with about the same electronic stopping power and about one order-of-magnitude difference in nuclear stopping power. The damage is dominated by the nuclear collision processes and rather well correlated with the estimated irradiation dose in dpa. Optical spectra show that electronic excitations induce damage recovery of the amorphized substrate below the SiC/Si interface. Raman spectra and optical absorption/reflection spectra yield complementary pictures of the radiation damage.

Anisotropy in the dielectric function of Bi2Te3 from first principles: From the UV-visible to the infrared range

The dielectric properties of ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$, a layered compound crystallizing in a rhombohedral structure, are investigated by means of first-principles calculations at the random phase approximation level. A special attention is devoted to the anisotropy in the dielectric function and to the local field effects that strongly renormalize the optical properties in the UV-visible range when the electric field is polarized along the stacking axis. Furthermore, both the Born effective charges for each atom and the zone center phonon frequencies and eigenvectors needed to describe the dielectric response in the infrared range are computed. Our theoretical near-normal incidence reflectivity spectra in both the UV-visible and infrared range are in fairly good agreement with the experimental spectra, provided that the free carriers Drude contribution arising from defects is included in the infrared response. The anisotropic plasmon frequencies entering the Drude model are computed within the rigid band approximation, suggesting that a measurement of the reflectivity in the infrared range for both polarizations might allow one to infer not only the type of doping but also the level of doping.

Optical, structural, electrical and photocatalytic properties of aluminum doped zinc oxide nanostructures

The Al-doped ZnO (Zn1-xAlxO, x = 0.00, 0.02, 0.04, 0.06, and 0.08) nanostructures were synthesized by the chemical vapor deposition technique. Analysis by X-ray diffraction reveals that both undoped and Al-doped ZnO nanostructures are crystallized in a single-phase wurtzite structure with a preferred orientation along the (101) plane. The addition of Al was studied to see how it influenced bond length, crystallite size, unit cell volume, lattice strain, and dislocation density. Field-emission scanning electron microscope imaging showed a significant variation in the morphology with increasing the Al doping level. Absorption spectra in the UV–Visible range revealed that introducing Al3+ ions into the ZnO lattice causes a blue shift in the optical band gap, which was explained according to Burstein-Moss effect and variation of the electronic structure. The direct electrical conductivity measurement showed a transformation between two conduction mechanisms upon variation of the temperature. Transition of the charge carriers from shallow and deep donor levels dominated in the low and high temperature ranges, respectively. The photodegradation rate constants and degradation efficiency were determined as well as the photocatalytic mechanism was described. Upon reaching the x = 0.08 Al doping level, the photocatalytic efficiency of the examined samples increased by 1.7-fold. The obtained results demonstrate that Al doping can tune the electrical, optical, and photocatalytic properties of ZnO nanostructures that make them applicable for many optoelectronic applications.

Near-infrared study of radiation damage in cerium dioxide

Radiation damage is studied in electron-irradiated cerium dioxide (CeO2) single crystals. Near Infra-red (NIR) spectra are recorded at room temperature between 2800 and 11,000 cm−1 (i.e. ∼0.9–3.57 µm in wavelength and ∼0.35–1.36 eV in photon energy). Measurements were carried out in the transmission mode for the single crystals and diffuse reflectivity mode for sintered CeO2 and (Ce, Gd)O2-x reference un-irradiated samples. The ceria single crystals were irradiated with 1.4-MeV and 2.5-MeV electrons for high fluences up to 3 × 1016 cm−2. Five broad absorption bands centered at 3600, 4100, 4600, 6000, and 7100 cm−1 (i. e. ∼0.44, 0.51, 0.57, 0.74, and 0.88 eV) are deduced from fits for the 2.5-MeV electron irradiation, whereas no absorption band is recorded for the 1.4-MeV electron energy. Those bands are consistent with the broad 0.9-eV band (7260 cm−1, 1.37 µm) in the UV–visible range associated with the change in color from light blue to deep green for the 2.5-MeV energy. Optical absorption arises from point-defect formation by elastic collisions for electron irradiation above the threshold energy near 1.4 MeV corresponding to the onset of cerium atom displacement. No defect bleaching occurs after isothermal annealing at 700 °C. No such bands are recorded for the virgin (Ce, Gd)O2-x samples for 5, 10, and 15 mol% Gd2O3 with an increasing amount of oxygen vacancies. The origin of absorption bands in the NIR range is discussed in relation to the available experimental data and ab-initio calculations of point defects in CeO2 and other dioxides with the cubic fluorite-like structure. Absorption bands are tentatively assigned to electronic transitions involving cerium vacancy levels in the band gap.

Water/oil nanoemulsion-based synthesis of BixSn6-2xSy (0.33 ≤ × ≤ 2.95) semiconductor QDs for efficient photocatalytic degradation of MB dye.

The development of efficient photocatalysts for the photodegradation of organic dyes in wastewater is highly worthwhile. Herein, the nanoemulsion tactic was utilized to synthesize BixSn6-2xSy (0.33 ≤ x ≤ 2.95) photocatalysts with morphological structures that changed from nanowhiskers to quantum dots (QDs). The optical properties of these materials were examined by UV-visible absorbance spectroscopy and photoluminescence, while Mott-Schottky analysis was utilized to study their electronic properties. BixSn6-2xSy materials exhibit appreciable absorption in the UV-visible light range with a direct band gap that increases from 1.23 to 1.46 eV. Both crystal structure and composition greatly affect the photocatalytic activity of BixSn6-2xSy semiconductors. Among the various synthesized photocatalysts, BiSn4S4.5 can efficiently photodegrade methylene blue dye (MB) in the shortest time under UV-visible light. The photocatalytic activity is positively affected by the change of crystal structure from orthorhombic to cubic symmetry. Based on the Mott-Schottky plots, the flat band potential (Efb) and the semiconductor behavior of the fabricated BixSn6-2xSy nanomaterials were determined. The obtained Efb values for SnS, Bi0.33Sn5.34S5.8, BiSn4S5.5, and Bi2.14Sn1.71S4.7 are -0.18 V, -0.42 V, -0.53 V, and -0.51 V (vs. Ag/AgCl), respectively. The Efb value is clearly shifted towards more negative potential values with increasing the Bi molar ratio (x). However, Bi2.95Sn0.1S4.5 semiconductor was found to be of n-type character, having a positive Efb value of +0.66 V (vs. Ag/AgCl). Photocurrent and EISresponses confirm the high stability and photocatalytic activity of BiSn4S5.5, which also achieves the lowest charge transfer resistance. The modified electronic properties of the BixSn6-2xSy semiconductors significantly improve their photocatalytic activity, rendering them to be promising absorbers for sunlight harvesting applications.

Structural and optical characterization of CH3NH3PbX3 (X= I, Br and Cl) powder as precursor materials for perovskite based optoelectronic devices

This work is a detailed report of the synthesis and characterization of high-quality CH3NH3PbX3(X = I, Br, and Cl) powders as precursor materials for perovskite based optoelectronic devices. MAPbX3 powders were synthesized through easy processing steps with simple precursors. The X-ray diffraction (XRD) analysis revealed that the synthesized materials possess a high degree of crystallinity. The MAPbI3 powder crystallizes in a tetragonal structure, while both MAPbBr3 and MAPbCl3 perovskite powders adopt a cubic structure with different lattice parameters. The three compounds are homogenous with well-defined atomic plans and high absorbance in the UV–Vis range, with bandgap energy around 1.48, 2.17 and 2.91 eV for MAPbX3 (X = I, Br and Cl, respectively). This work is a detailed characterization of MAPbX3 lab-synthesized materials to pave the way toward their commercialization as precursors for perovskite based optoelectronic devices.

Boron-rich triphenylene COF based electrides having excellent nonlinear optical activity

The desirability of the high nonlinear response of two-dimensional (2D) materials for electronics and optoelectronic devices drove us to investigate the nonlinear optical (NLO) behavior of alkali metal atom (AA) doped lithiated boron-containing hexahydroxy-triphenylene (LiBHHTP). In this context, the geometric, electronic, optical, and NLO properties are investigated. The doped AA atoms including Li, Na, and K preferably interact via the oxygen atoms of the LiBHHTP surface. The stability of the doped complexes is revealed by the interaction energies (Eint), which are −22.90, −16.10, and −16.52 kcal/mol for Li@LiBHHTP, Na@LiBHHTP, and K@LiBHHTP complexes, respectively. The alterations in the electronic behavior of LiBHHTP are observed upon doping with alkali atoms via Frontier Molecular Orbital (FMO), Natural Bond Orbital (NBO), and the Density of State (DOS) analyses. The FMO analysis reveals that these complexes are electride in nature with absorption transparency in the UV–Vis range. Finally, the NLO behavior of designed complexes is evaluated through static and dynamic hyperpolarizabilities. Among reported complexes, K@LiBHHTP exhibits significantly large static hyperpolarizability (βₒ), 2.24 × 105 au. The dynamic NLO response of doped LiBHHTP complexes is also high, where the values are ranged in between 3.67 × 105 and 6.04 × 108 au at 1064 nm. This article not only highlights the effects of alkali atom doping on the NLO behavior of materials but also presents the first Lithiated boron-containing triphenylene as a next-generation optoelectronic material.

Improvement of photocatalytic degradation of methyl orange by impregnation of natural clay with nickel: optimization using the Box-Behnken design (BBD)

In this research work, the photocatalytic degradation of methyl orange dye was studied on nickel oxide supported on a natural Moroccan clay (Ni/NC). These catalysts have been prepared by dry impregnation of a nickel nitrate solution with different weight percentages (5, 10, 20% NiO). Experimental responses were obtained by a Box-Behnken (BBD) experimental design by varying the catalyst mass, solution pH, and initial dye concentration at three levels (low, medium, and high). The prepared catalysts were characterized using powder X-ray diffraction (XRD) to assess crystallinity and structure, Fourier transform infrared spectroscopy (FTIR) to detect different functional groups, scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX) analysis to study the surface morphology, and the optical characteristics of the catalysts were studied using absorption and diffuse reflectance measurements in the UV-visible range. The photocatalytic activity of the catalysts was evaluated in aqueous solutions under UV irradiation. ANOVA (analysis of variance) test is employed to recognize the significant factors and their interactions and then give the model equation for the percent dye degradation. The optimal values of the studied factors were determined by numerical optimization, and the results showed that about 100% degradation of the methyl orange dye could be achieved under the following optimal conditions, which are pH = 4.38, catalyst concentration of 0.99g/L, and initial dye concentration of 30.42mg/L.

Sulfidogenic Bioreactor-Mediated Formation of ZnS Nanoparticles with Antimicrobial and Photocatalytic Activity

The use of sulfidogenic bioreactors is a biotechnology trend to recover valuable metals such as copper and zinc as sulfide biominerals from mine-impacted waters. In the present work, ZnS nanoparticles were produced using "green" H2S gas generated by a sulfidogenic bioreactor. ZnS nanoparticles were physico-chemically characterized by UV-vis and fluorescence spectroscopy, TEM, XRD and XPS. The experimental results showed spherical-like shape nanoparticles with principal zinc-blende crystalline structure, a semiconductor character with an optical band gap around 3.73 eV, and fluorescence emission in the UV-visible range. In addition, the photocatalytic activity on the degradation of organic dyes in water, as well as bactericidal properties against several bacterial strains, were studied. ZnS nanoparticles were able to degrade methylene blue and rhodamine in water under UV radiation, and also showed high antibacterial activity against different bacterial strains including Escherichia coli and Staphylococcus aureus. The results open the way to obtain valorous ZnS nanoparticles from the use of dissimilatory reduction of sulfate using a sulfidogenic bioreactor.

Black Silicon: Breaking through the Everlasting Cost vs. Effectivity Trade-Off for SERS Substrates

Black silicon (bSi) is a highly absorptive material in the UV-vis and NIR spectral range. Photon trapping ability makes noble metal plated bSi attractive for fabrication of surface enhanced Raman spectroscopy (SERS) substrates. By using a cost-effective room temperature reactive ion etching method, we designed and fabricated the bSi surface profile, which provides the maximum Raman signal enhancement under NIR excitation when a nanometrically-thin gold layer is deposited. The proposed bSi substrates are reliable, uniform, low cost and effective for SERS-based detection of analytes, making these materials essential for medicine, forensics and environmental monitoring. Numerical simulation revealed that painting bSi with a defected gold layer resulted in an increase in the plasmonic hot spots, and a substantial increase in the absorption cross-section in the NIR range.

Zinc Oxide Films Fabricated via Sol-Gel Method and Dip-Coating Technique-Effect of Sol Aging on Optical Properties, Morphology and Photocatalytic Activity.

Zinc oxide layers on soda-lime glass substrates were fabricated using the sol-gel method and the dip-coating technique. Zinc acetate dihydrate was applied as the precursor, while diethanolamine as the stabilizing agent. This study aimed to determine what effect has the duration of the sol aging process on the properties of fabricated ZnO films. Investigations were carried out with the sol that was aged during the period from 2 to 64 days. The sol was studied using the dynamic light scattering method to determine its distribution of molecule size. The properties of ZnO layers were studied using the following methods: scanning electron microscopy, atomic force microscopy, transmission and reflection spectroscopy in the UV-Vis range, and the goniometric method for determination of the water contact angle. Furthermore, photocatalytic properties of ZnO layers were studied by the observation and quantification of the methylene blue dye degradation in an aqueous solution under UV illumination. Our studies showed that ZnO layers have grain structure, and their physical-chemical properties depend on the duration of aging. The strongest photocatalytic activity was observed for layers produced from the sol that was aged over 30 days. These layers have also the greatest porosity (37.1%) and the largest water contact angle (68.53°). Our studies have also shown that there are two absorption bands in studied ZnO layers, and values of optical energy band gaps determined from positions of maxima in reflectance characteristics are equal to those determined using the Tauc method. Optical energy band gaps of the ZnO layer fabricated from the sol aged over 30 days are EgI = 4.485 eV and EgII = 3.300 eV for the first and second bands, respectively. This layer also showed the highest photocatalytic activity, causing the pollution to degrade 79.5% after 120 min of UV irradiation. We believe that ZnO layers presented here, thanks to their attractive photocatalytic properties, may find application in environmental protection for the degradation of organic pollutants.

Specific fluorescent signatures for body fluid identification using fluorescence spectroscopy

Non-invasive, rapid, on-site detection and identification of body fluids is highly desired in forensic investigations. The use of fluorescence-based methods for body fluid identification, have so far remain relatively unexplored. As such, the fluorescent properties of semen, serum, urine, saliva and fingermarks over time were investigated, by means of fluorescence spectroscopy, to identify specific fluorescent signatures for body fluid identification. The samples were excited at 81 different excitation wavelengths ranging from 200 to 600 nm and for each excitation wavelength the emission was recorded between 220 and 700 nm. Subsequently, the total emitted fluorescence intensities of specific fluorescent signatures in the UV–visible range were summed and principal component analysis was performed to cluster the body fluids. Three combinations of four principal components allowed specific clustering of the body fluids, except for fingermarks. Blind testing showed that 71.4% of the unknown samples could be correctly identified. This pilot study shows that the fluorescent behavior of ageing body fluids can be used as a new non-invasive tool for body fluid identification, which can improve the current guidelines for the detection of body fluids in forensic practice and provide the robustness of methods that rely on fluorescence.

Re-structuring of glass surface by ion post-embedding for transmission improvement and application in solar panels

Inspired by ion-exchange technology as a means to chemical strengthening glass, alkali ions (K+) were, herein, superficially embedded into photovoltaic (PV) glass under certain thermal treatment conditions, and the evolution of the surface morphology and roughness was evaluated. The restructured surface exhibited enhanced transmission in the UV–Vis range. Ions penetrating the glass surface induced the dissociation of tetrahedral Si–O to form a new pole pair with a new non-bridging oxygen anion. The permittivity–frequency plots indicate a reduction in the dielectric constant of the entire glass and a consequent reduction in the refractive index. These changes may be the root cause of the transmission improvement. The PV performance was evaluated using sealed 2.25 cm2 perovskite solar cells, where current and consequent efficiency improvements are obtained. This thermal ion-invasion method is also compatible with standard anti-reflection porous SiO2 coating in PV glass production.

X-Ray Crystallography, Spectral Analysis, DFT Studies, and Molecular Docking of (C9H15N3)[CdCl4] Hybrid Material against Methicillin-Resistant Staphylococcus aureus (MRSA)

The one dimensional polymer complex (C9H15N3)[CdCl4], was synthesized and characterized by X-ray crystallography, FT-IR vibrational, and thermal analysis, UV–Visible and photoluminescence (PL) spectroscopic investigations. The crystal structure crystallizes in the monoclinic space group C2/c with Z = 4. The experimental geometric data of the crystalline molecule and the results of density functional theory (DFT) generated utilizing computational methods at DFT/ωB97XD and DFT/B3LYP-D3/Gen/6-311++G(d, p)//LanL2DZ levels of theory were compared. Significantly, in order to reveal the vibrational modes of the named chemical, the Infrared and Raman spectra were registered. Then, 13C and 113Cd solid-state NMR was employed to characterize this hybrid material using a polar solvent to conduct an investigation of the optical characteristics for the UV–visible range. Consequently, utilizing the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO) calculations, the molecule’s energy gap (Eg) was determined. More so, the PL tests revealed two peaks at about 400 and 423 nm while the Hirshfeld surface (HS) analysis and DFT calculations were also carried out to acquire insight into the role of weak molecular interactions in the complex that affect the self-assembly process and crystal packing. In addition, molecular docking experiments with the 6U3Y, 1SAX, and 2D45 receptors reveal ideal postures with intriguing binding affinities of −5.2, −5.6, and −5.7 kcal.mol−1, respectively. Lastly, thermo-differential analysis techniques (DTA) and thermogravimetric analysis techniques (TGA) were used to account for the thermal degradation of the current complex.

Development and validation of UV-spectrophotometric method for estimation of pterostilbene in Pterocarpus marsupium

Aim: To develop and validate a simple, precise and cost effective UV-visible spectrophotometric method for the estimation of pterostilbene in Pterocarpus marsupium extract. All the parameters of the analysis were chosen as per ICH Q2 (R1) guideline. Methods: Pterostilbene solution was scanned over UV-visible range for its wavelength of maximum absorbance. Various calibration standards of pterostilbene were prepared. Calibration curve of concentration vs. absorbance was plotted and developed UV – visible spectrophotometry method was used for estimation of pterostilbene in standardized Soxhlet assisted extract (SAE)as well as ultrasound assisted extracts (UAE) of Pterocarpus marsupium. Results: The maximum wavelength of pterostilbene was found to be 306 nm. The correlation coefficient of developed UV-Visible spectrophotometric method over the concentration range of 1-6 μg/ml was found to be 0.999. The validation study of the said method was carried out in terms of linearity, accuracy, precision, robustness, ruggedness, limit of detection and limit of quantitation studies. Developed UV – visible method was found to be precise for the intra- and inter- day studies and showed standard deviation in the range of 0.83 to 1.912&0.762 to 1.542respectively. The pterostilbene content in Pterocarpus marsupium extract was found to be 4.5% using the proposed UV – visible spectrophotometry method. Conclusion: A simple, precise and cost-effective UV- visible spectrometry method was developed for the estimation of pterostilbene in standardized extract of Pterocarpus marsupium. The method was developed using solvent containing economical percentage of organic phase in aqueous media. Said validated UV- visible method can be efficiently used for the estimation of pterostilbene in extracts of Pterocarpus marsupium.

Bioynthesis of silver nanoparticles using Dunaliella salina and its antibacterial applications

In this study, an aqueous extract of Dunaliella salina was used to reduce silver nitrate and create silver nanoparticles (AgNPs). Silver nanoparticles were created as soon as silver particles made in contact with the microalgae extract, showing the speedy preparation process. The microalgae extract was prepared and used for biosynthesis of silver nanoparticles. Synthesized nanoparticles were characterized using UV–Vis, SEM-EDX, XRD and FTIR analysis. Antibacterial assays were performed using disc-diffusion method. A peak at 454 nm was found in the UV–Vis range of the aqueous media containing silver particles, which was related to the plasmon absorbance of AgNPs. Scanning electron microscope (SEM) demonstrated size of 35 nm of AgNPs. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of AgNPs, which revealed a solid flag in the silver region. X-ray diffraction (XRD) confirmed the formation of crystalline nanoparticles. The presence of functional groups in AgNPs was confirmed using Fourier transform infrared (FTIR) analysis. Antibacterial property of synthesized nanomaterials was also found to have a possible antibacterial effects on Escherichia coli, Bacillus subtilis, as well as Enterobacter tobbaci. Thus, silver nanoparticles were biosynthesized using Dunaliella salina microalgae extract and tested for antibacterial effects.

Low-Ag-content Ni3N-Ni/Ag@C catalyst for the reduction of 4-nitrophenol

BackgroundCatalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) is a recurrent topic. The most promising catalysts are often regarded as noble metals. But maintaining high catalytic performance while reducing the number of noble metals remains a significant difficulty. Here, a 0.6 weight percent (wt%) Ag-based catalyst was used to catalyze the reduction of 4-NP in contaminated water. MethodsUsing a one-step urea-glass method and annealing at 380 °C, Ni3N-Ni heterostructures were implanted in a carbon matrix, and subsequently Ag nanoparticles were introduced to the Ni3N-Ni@C by galvanically substituting Ni for AgNO3. Spectra in the UV-vis range were employed to track the reduction reaction. Investigations were done into how both inorganic and organic species affected catalytic effectiveness. Significant ResultsCompared to Ni3N-Ni@C and Ni/Ag (0.6 wt%)@C, Ni3N-Ni/Ag (0.6 wt%)@C displayed good catalytic activity and stability toward 4-NP reduction with a rate constant of 8.1 × 103 s−1 g−1Ag. The catalytic efficiency was essentially unaffected by the interferents. The catalyst could quickly purify lake water that was contaminated with very concentrated 4-NP (140 ppm) in about 6 min.