X-ray Diffraction Methods Research Articles

Оптимизация режимов селективного лазерного плавления порошковой композиции системы AlSiMg

Introduction. New aluminum-based powder systems are currently being developed for additive manufacturing. The scientists' work is aimed at comprehensive studies of powder production, optimization of conditions for alloy production and formation of three-dimensional specimens with minimal porosity and absence of cracking during selective laser melting. The purpose of this work is the synthesis of an almost spherical Al-Si-Mg composite powder (91 wt. % Al, 8 wt. % Si, 1 wt. % Mg) from aluminum powder PA-4 (GOST 6058-22), silicon powder (GOST 2169-69) and magnesium powder MPF-4 (GOST 6001-79), which were not originally intended for selective laser melting technology. The work also provides for the optimization of selective laser melting modes to obtain an alloy and form three-dimensional specimens with minimal porosity and no cracking. To create a powder composition, powders ranging in size from 20 to 64 μm were selected by sieve analysis and subjected to mechanical mixing in a ball mill in a protective argon medium for one hour. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy, mechanical tests of microhardness. Studies of the powder composition after mechanical mixing showed that the mixed powder of aluminum, silicon and magnesium is a conglomerate of particles of spherical, oval and irregular shape. Results and discussions. The optimal modes for obtaining a specimen with a minimum porosity of 0.03 % and a microhardness of 1,291 MPa are selective laser melting modes: P = 90 W, V = 225 mm/s, S = 0.08 mm, h = 0.025 mm. The conducted research shows the possibility of synthesizing products from metal powders that are not adapted to processing by selective laser melting and obtaining an alloy with new mechanical properties during laser action.

Zeta Potential and Size Analysis of Zeolitic Imidazolate Framework-8 Nanocrystals Prepared by Surfactant-Assisted Synthesis.

The crystal nucleation and growth mechanism of monodispersed metal-organic framework nanoparticles were studied using time-resolved light dynamic, electrokinetic, and powder X-ray diffraction methods. We confirmed that zeolitic imidazolate framework-8 (ZIF-8) nanocrystals follow a nonclassical crystal growth pathway, where a fast nucleation occurs with dense liquid clusters or nanocrystals forming spontaneously when two precursors are mixed. We also explored the zeta potential and solvodynamic size changes of ZIF-8 prepared by a surfactant-assisted synthesis. Three modulators, including 1-methylimidazole (1-mIm), tris(hydroxymethyl)aminomethane (THAM), and (1-hexadecyl)trimethylammonium bromide (CTAB), were studied. We found that 1-mIm dramatically increases the rate of nucleation of ZIF-8. With an increasing amount of 1-mIm, which functions as a coordination modulator, the size increases, and the zeta potential of ZIF-8 decreases. Whereas THAM, as both a coordination and a deprotonation modulator, increases the size and zeta potential of ZIF-8 simultaneously, CTAB, as a long alkyl cationic surfactant, mainly adsorbs on the surface of ZIF-8, and the zeta potential of the formed ZIF-8 is controlled by the amount of CTAB in solution compared with its critical micelle concentration. Overall, we reveal that the modulator type and concentration can be used to control the size and zeta potential of the dispersed ZIF-8 nanocrystals in a colloid system. The experiments also enable identification of the nucleation and crystal growth processes of ZIF-8. The findings will be applicable to other nanocrystals in colloid systems, which are used for heterogeneous catalysis and guest molecular loadings.

Synthesis of spiro[piperidine-4,3′-pyrrolo[3,4-c]quinolines via 1,3-dipolar cycloaddition of azomethine ylides and 3-Nitro-2(1H)-quinolones

The 1,3-dipolar cycloaddition of 3-nitro-2(1H)-quinolones and β-nitro-styrenes with azomethine ylides derived from sarcosine and benzyl 4-oxopiperidine-1-carboxylate have been investigated. The structure of the formed cycloadducts were studied in detail by X-ray diffraction and NMR spectroscopy methods. This process is a solid and versatile strategy for rapidly assembling quinoline fused pyrrolines scaffold with a spiropiperidine part containing orthogonal diversification points for further substitutions.

Residual Stress Measurements in Tensile Armours of Flexible Pipes by the Contour and X-Ray Diffraction Methods

Residual Stress Measurements in Tensile Armours of Flexible Pipes by the Contour and X-Ray Diffraction Methods

ON/OFF based synergetic plasmonic photothermal drug release approach through core-satellite like mussel-inspired polydopamine nanoparticles

One of the studies on new drug delivery and release systems that has increased in recent years is the study using plasmonic nanoparticles. In this study, polydopamine nanoparticles (PDOP NPs), which contribute to photothermal drug release by near infrared radiation (NIR), were decorated with gold nanoparticles (AuNPs) to utilize their plasmonic properties, and a core-satellite-like system was formed. With this approach, epirubicin (EPI)-loaded PDOP NPs were prepared by utilizing the plasmonic properties of AuNPs. Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) methods were used to evaluate the structural properties of these particles. The release behavior of the prepared structures in acidic (pH 5.0) and neutral (pH 7.4) environments based on the ON/OFF approach was also examined. The biocompatibility properties of the particles were evaluated on mouse fibroblast (L929) and anticancer activities on neuroblastoma (SH-SY5Y) cells. The effects of prepared EPI-loaded particles and laser-controlled drug release on ROS production, genotoxicity, and apoptosis were also investigated in SH-SY5Y cells. With the calculated combination index (CI) value, it was shown that the activity of EPI-loaded AuNP@PDOP NPs increased synergistically with the ON/OFF-based approach. The developed combination approach is considered to be remarkable and promising for further evaluation before clinical use.

Pyridine-assisted electrodeposition of Au(1 1 1)-dominant gold nanonetworks on glassy carbon electrode for anodic stripping voltammetry analysis of As(III), Se(IV) and Cu(II)

Gold nanonetworks with Au(111)-dominant facets (AuNNs(1 1 1)-D) modified glassy carbon electrode (GCE) was simply fabricated by electroreduction of Au(III) with the assistance of pyridine (Py). Cyclic voltammetry of Au(III)-Py complex exhibits two sequential cathodic peaks, reflecting the reduction of Au(III) to Au(I) intermediate and then to Au(0). The as-prepared AuNNs(111)-D/GCE was characterized by scanning electron microcopy, X-ray diffraction and electrochemistry methods, and the results showed that the gold crystalline spread out in a nanonetworks architecture with good distribution, high aspect-ratios, large roughness and 90 % Au(111) facets. The coordination effects of Py, the inferior affinity of Py on Au(111) facets and the sustained generation of Au(I) intermediate contributed to such gold nanoarchitecture. Differential pluse anodic stripping voltammetry analysis of As(III), Se(IV) and Cu(II) was performed on the AuNNs(1 1 1)-D/GCE with high performance. Sensitivity values of 16.9 µA μM−1 (As(III)), 9.51 µA μM−1 (Se(IV)), 6.09 µA μM−1 (Cu(II)), as well as limit of detection values of 0.67 nM (As(III)), 1.1 nM (Se(IV)), 0.53 nM (Cu(II)) were obtained (S/N = 3), respectively. The AuNNs(111)-D/GCE was used for As(III), Se(IV) and Cu(II) determination in real drinkable water samples with satisfied results.

Development of Poly(vinyl alcohol)-Chitosan Composite Nanofibers for Dual Drug Therapy of Wounds.

Current trends in localized drug delivery are emphasizing the development of dual drug-loaded electrospun nanofibers (NFs) for an improved therapeutic effect on wounds, especially infected skin wounds. The objective of this study was to formulate a new healing therapy for an infected skin wound. To achieve this goal, this study involved the development and characterization of poly(vinyl alcohol) (PVA)/chitosan nanofibers loaded with ciprofloxacin and rutin hydrate. Polymers and drugs were used in different ratios. Nanofiber morphology was studied by scanning electron microscopy, thermal stability by thermogravimetric analysis, structural determination by the X-ray diffraction method, and integrity by Fourier transform infrared spectroscopy. Dissolution studies were performed to check the drug release behavior of the formulations. Antibacterial studies were performed against Staphylococcus aureus and Pseudomonas aeruginosa. The wound healing efficiency of dual drug-loaded nanofibers was measured by a full-thickness excisional wound model of rabbits. The fabricated nanofibers were smooth in morphology. According to FTIR findings, the drugs remained intact in the nanofibers. The results of swelling ratio and porosity revealed that the pore size was increased as the amount of chitosan was increased up to 30% but a further increase in chitosan concentration reduced the swelling ratio and porosity. Drug release studies of nanofibers depicted an initial burst effect and afterward controlled drug release behavior. Drug-loaded nanofibers showed better activity against S. aureus than P. aeruginosa. The antibacterial efficacy of rutin hydrate with ciprofloxacin was improved compared to that of the formulation having rutin hydrate only, likely due to the additive effect in activity. Based on wound healing studies, nanofibrous membranes acted as a promising wound dressing material as compared to the commercial wound healing formulation. Drug-loaded polymeric nanofibers were successfully fabricated by using an electrospinning method. These nanofibers showed an efficient ability to deliver drugs and treat infected wounds.

Preparation of FeNiCoCrCu Thin Films by Ionized Jet Deposition Method: Determination of Elemental Transfer Coefficients

Investigation of high-entropy alloys in form of bulk samples as well as thin films is currently one of the fastest growing areas in the study of metal alloys. In this paper, a bulk sample of FeNiCoCuCr high-entropy alloy ingot with equimolar composition is prepared by the laboratory arc melting method under an argon atmosphere and used as a source target for deposition of thin films on Si (111) single-crystalline substrates using a novel ionized jet deposition method. The morphology, chemical composition, and real crystalline structure of the target and the prepared layers were characterized by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectroscopy, and X-ray and neutron diffraction methods. Transfer coefficients characterizing the mass transport between the target and the grown film were calculated for each of the constituting metallic elements as the ratio of the atomic concentration found in the prepared film divided by its concentration in the deposition target. The dependence of the obtained transfer coefficients on the IJD acceleration voltage is discussed with respect to the main physical and geometric parameters of the deposition process, and their correlations with the cohesive energy of the elements forming the HEA are proposed.

Chalcone-based novel mono and bisthiocarbohydrazone: synthesis, crystal structure, antioxidant property and theoretical evaluation

This study describes the synthesis of novel chalconethiocarbohydrazones derived from 2′-hydroxychalcone and thiocarbohydrazide as potential drugs. The monothiocarbohydrazone (M1) and bisthiocarbohydrazone (M2) compounds were obtained by condensing thiocarbohydrazide with 2′-hydroxychalcone [1-(2-hydroxyphenyl)−3-phenyl-2-propen-1-one] at 1/1 and 1/2 mol ratios. The synthesized compounds were characterized by elemental analysis, 1H NMR, FT-IR and UV-Vis spectroscopic techniques. The crystal structures of M1 and M2 were solved using single crystal X-ray diffraction method. The total antioxidant capacities of synthesized thiocarbohydrazones were determined by Cupric Reducing Antioxidant Capacity (CUPRAC) method. It was investigated also the radical scavenging activities of these compounds with 2,2-Diphenyl-1-picrylhydrazyl (DPPH) method. When compared to standard compound Trolox, both of the compounds showed good antioxidant activity. For the new compounds, Conceptual Density Functional Theory (CDFT) computations were performed to compute important quantum chemical reactivity descriptors. The chemical reactivities of the studied chemical systems were compared via well-known electronic structure rules of CDFT. Experimentally determined antioxidant activities of the synthesized compounds were supported with Molecular Docking analyses.

CeO2 NANOTANECİKLERİNİN SENTEZİ, KARAKTERİZASYONU VE FOTOKATALİTİK AKTİVİTESİ

The discharge of untreated wastewater from unplanned industrial activities using dyes can cause serious environmental pollution and affect the aquatic environment. Semiconductor photocatalysis is a favorable technology widely used for degrading organic dyes in wastewater. This study dealt with the preparation of CeO2 nanoparticles via a simple precipitation technique. Information on the structural and morphological features of the developed CeO2 nanoparticles were determined using Fourier transform infrared with attenuated total reflectance (FTIR-ATR), Raman spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) spectroscopic methods. The presence of the characteristic bands of CeO2 in the FTIR spectrum provided evidence of successful CeO2 formation. The calculated crystallite particle size utilizing the Scherrer equation was 10 nm. SEM images revealed that the morphology of CeO2 consisted of almost spherical particles with slight agglomeration. Brunauer-Emmett-Teller (BET) technique was also used to find out the specific surface area of CeO2 nanoparticles (11 m2/g). The efficiency of CeO2 nanoparticles was also confirmed in terms of their photocatalytic activity against Rhodamine B (Rh B) under UV-A light. The results indicated that CeO2 nanoparticles could be a promising catalyst candidate for industrial wastewater treatment.

Novel nanocomposite systems based on cesium dihydrogen phosphate: Electrotransport structural, morphological and mechanical characteristics

CsH2PO4 is a proton conductor belonging to the family of acidic salts and exhibits a monoclinic to cubic phase transition at 230 ± 2 °C with the conductivity jump of four orders of magnitude. To change the electrotransport and mechanical characteristics the non-oxide additives, such as detonation nanodiamonds, were firstly used as a dopant for proton nanocomposites based on cesium dihydrogen phosphate. The use of carbon containing materials has made it possible to create a new type of medium-temperature, highly conductive proton electrolytes. Influence of nanodiamonds (NDs) on the electrotransport, structural and thermodynamic properties of (1-x)CsH2PO4-xNDs (x-mole fraction, x = 0–0.99) electrolytes have been firstly investigated in detail by X-ray diffraction method, electrochemical impedance, FTIR-spectroscopy and differential scanning calorimetry. The CsH2PO4 (P21/m) exists in nanocomposites in the dispersed (up to 300 nm) and partially amorphous state resulting in the strong changes of the salt thermodynamic properties with increase of x mole fraction. The heterogeneous doping by non-oxide dopant resulted in the significant increase of the low temperature conductivity of 3.5 orders of magnitude due to interface interaction, while the superionic conductivity of nanocomposites remains close to the individual CsH2PO4 (∼10-2 S/cm) up to x = 0.7 (fvNDs = 11.7 %). The jump in the conductivity during the phase transition decreases significantly and almost disappears. The conductivity of nanocomposites decreases significantly only at x > 0.95 (fvNDs = 51.8 %) due to the percolation effect. The mechanical properties of CsH2PO4-NDs were shown to be much higher than of the individual CsH2PO4 even with small NDs content. Mechanism of nanocomposites formation is associated with the partial binding of CsH2PO4 protons by surface OH– groups of nanodiamonds. The results are important for the establishing and design the next generation membrane of fuel cells and nanocomposite electrodes for medium-temperature electrochemical devices.

Novel bulk triaxial residual stress mapping in an additive manufactured bridge sample by coupling energy dispersive X-ray diffraction and contour method measurements

A novel approach for determining triaxial residual stress states by coupling energy dispersive X-ray diffraction and contour method measurements is provided and validated in a Ti‐5Al‐5V‐5Mo‐3Cr additive manufactured (AM) bridge sample. Synchrotron X-ray diffraction (SXRD) can provide relatively fine spatial resolution (on the order of 10–100 µm) for mapping 3D elastic strain fields within a sample. However, for samples with dimensions larger than one or two centimeters the path length can get prohibitive as both constant wavelength and energy dispersive SXRD are based upon transmission measurements. As an example, for a plate-like sample geometry where the thickness is limited (less than a centimeter) it is trivial to measure the longitudinal and height direction elastic strain components with excellent in-plane spatial resolution (∼100 µm) and a somewhat lower through-thickness resolution (10–15 times larger) but obtaining the through thickness component is often not possible as the beam path must be parallel to one of the large dimensions of the plate. While small samples of low Z-number alloys (e.g., Ti or Al) allow determination of the three elastic strain components, this is often not the case for higher Z alloys (e.g., Fe or Ni) or large samples where some strain components can be indeterminable. To overcome these limitations, this work applies a combination of synchrotron X-ray diffraction and the contour method (a mechanical relaxation technique), to determine the triaxial stress state. This novel combination is demonstrated and validated in a relatively small additive manufactured sample where all three orthogonal strain components are accessible via X-ray diffraction for stress determination. The paper also explores methods for determining the strain-free lattice parameter, typically obtained from a small stress-free reference sample. This work shows that a small size AM sample is not stress free, producing unreliable magnitudes of strain and stress. Instead, a strain-free lattice parameter is determined using residual stress equilibrium conditions, which gives consistent strain and stress trends for both X-ray diffraction (alone) and the new diffraction-contour coupling technique. This demonstrates that the coupling technique can be confidently applied to samples to determine stress when path length (size or Z-number) prohibit determination of three orthogonal strain components via diffraction.

The influence of boron and silicon on the phase transformations of fullerene C60 at high temperatures and pressure

The effect of doping with two carbide-forming nonmetals - Si or B - (7 at. % each) on the phase transformations of crystalline C60 fullerene at a pressure of 8 GPa in the temperature range of 400–950 °C was studied using the X-ray diffraction method. Samples were synthesized from powders in a high pressure toroidal chamber, and X-ray examination was carried out at room temperature after rapid cooling. It has been shown that doping does not change the sequence of phase transformations of C60 fullerene as the temperature increases, the following phases are still observed: fcc phase - rhombohedral phase – disordered (amorphous) graphite. Boron reduces the formation temperature of disordered graphite, but silicon does not. This influence of carbide-forming non-metallic elements is fundamentally different from the influence of carbide-forming metals – Al and Fe, the addition of which increases the stability of fullerene molecules and increases the temperature of its transformation into disordered (amorphous) graphite by hundreds of degrees (P. A. Borisova, M. S. Blanter, V. V. Brazhkin, and V. P. Filonenko, Phase Transformations in C60 Fullerene with Iron and Aluminum at High Pressures and Temperatures, Bulletin of the Russian Academy of Sciences: Physics, 84 (2020) 851–856).

SYNTHESIS OF NICKEL-DOPED BIVO4 MATERIALS BY HYDROTHERMAL METHOD AND EVALUATE THE PHOTOCATALYTIC ABILITY TO DECOMPOSE METHYLENE BLUE UNDER VISIBLE LIGHT

Ni-doped BiVO4 photocatalysts were successfully synthesized by hydrothermal method. The catalytic samples were characterized by scanning electron microscopy (SEM), UV-vis diffuse reflection spectroscopy (DRS), photoluminescence spectroscopy (PL) and X-ray diffraction (XRD). Based on the results of PL spectrum analysis, the electron-hole recombination phenomenon is limited by the presence of the second metal Ni in the structure at Bi3+ positions. The catalyst materials at the Ni doping ratios all have the monoclinic-scheelite BiVO4 structure as shown by the XRD and Raman methods. The photocatalytic ability of methyl blue (MB) on the Ni/BiVO4 catalyst was studied under visible light irradiation in order to contribute to reducing the current environmental pollution problem. The removal efficiency of MB varies with the doping ratio of Ni/BiVO4, reaching the highest decomposition efficiency of 84.77% in the 5% mol Ni sample, which is 30% higher than that of the BiVO4 sample. The BiVO4 material modified with Ni gives a high photocatalytic efficiency of organic pigment decomposition under visible light indicates the potential improvement in the efficiency of a material for existing applications and exploit many new applications in the future.

Acoustic emission features of granite from different rockburst areas in Sangzhuling Railway Tunnel

In order to investigate the acoustic emission (AE) features of rocks in different (medium and strong) rockburst areas, the Sangzhuling Railway Tunnel granite in China was taken as an example, the mineral composition of rocks in different rockburst areas was analyzed by using XRD (X-ray diffraction) method. The Original rock cores of different rockburst areas were processed into standard rock specimens (diameter 50 mm, height 100 mm) in different directions (transverse, oblique and longitudinal). AE feature parameters (event number, ringing count and energy) of standard rock specimens during indoor uniaxial compression test were obtained by using AE technique. The variation law of AE feature parameters of rocks in different rockburst grade areas was then analyzed. The AE features of failure precursor of rocks in different rockburst areas were therefore discussed. It shows that compared with rocks in medium rockburst area, the content of quartz and feldspar of rocks in strong rockburst area is high, while the content of biotite is low; the rock in the strong rock burst area released more energy during the failure process with about 2–3 times that of the rock in the medium rock burst area; the cumulative ringing curve of rock in medium burst area is a stepped type, while the cumulative ringing curve of rock in strong burst area is the smoothed type; the end of the second and first AE quiet period may be regarded as the failure precursor of rocks in medium and strong rockburst area, respectively. The results presented herein are important for understanding the mechanisms of rockburst.

PROCEDURE FOR DETERMINING THE NATURE OF CALCIUM CARBONATE FORMATION ON OILFIELD EQUIPMENT

In the article, the authors propose to use the method of X-ray diffraction analysis (XRD) to establish the nature of the formation of oilfield deposits using of calcium carbonate as an example. It was shown for the first time that comparative diffraction patterns of natural and technogenic carbonate mineral deposits of oilfield equipment differ significantly in the physical broadening of diffraction reflections. In addition, it has been established that the diffraction reflections of technogenic calcite are characterized by shifts to the region of large scattering angles. These facts are taken as the basis for establishing the nature of the formation of carbonate deposits using X-ray diffraction analysis. It has been shown that natural (core) carbonate minerals are characterized by narrow reflections with good resolution of doublet lines, while in minerals formed under borehole conditions, the diffraction maxima are much broader, and low-intensity reflections are not resolved. Precision analysis of diffraction patterns showed that the reasons for such atypical broadenings and shifts of reflections in technogenic mineral deposits are the relatively small sizes of grains — crystallites and high microdistortions of the crystal lattice compared to their natural analogues. It is shown that in order to establish the nature of carbonate deposits of oilfield equipment, it is necessary to measure diffraction patterns of natural and technogenic minerals under the same shooting conditions. Subsequently, the obtained diffraction patterns are analyzed and X-ray diffraction data on the microstructure of the studied minerals are determined. It has been established that in technogenic calcite the crystallite sizes in all arbitrarily selected directions (hkl) are more than 1.6 times smaller than in its natural analogue. The X-ray diffraction method has shown that the average value of microdistortion of the crystal lattice of technogenic calcite is 1.7 times greater than that of its natural analogue. As a result of comparing X-ray diffraction data on the fine structure of mineral deposits of oilfield equipment with those obtained from core material, the nature of the formation of the analyzed minerals is established. To confirm the XRD results, visual studies using scanning electron microscopy (SEM) were also carried out.

Influence of the Applied External Magnetic Field on the Deposition of Ni–Cu Alloys

Ni–Cu alloys are suitable candidates as catalysts in hydrogen evolution reaction. Because of the different magnetic properties of Ni and Cu, the influence of an applied external magnetic field on the synthesis Ni–Cu alloys was studied. The coatings were prepared with visible changes in their appearance. The differences between the observed regions were studied in terms of morphology and chemical composition. In addition, the overall chemical and phase compositions were determined using X-ray fluorescence and X-ray diffraction methods, respectively. The catalytic activity was measured in 1 M NaOH using linear sweep voltammetry. The contact angle was determined using contour analysis. All samples were hydrophilic. Hydrogen evolution started at different times depending on the area on the surface. It started earliest on the coating obtained in parallel to the electrode magnetic field at 250 mT. We found that when the Lorenz force is maximal, Cu deposition is preferred because of the enhancement of mass transport.

Gamma radiation-induced alterations in nanocrystalline titanium nitride (TiN) particles: A structural perspective

The effect of gamma radiation on the structure of nanocrystalline TiN particles was studied. Initially, nanocrystalline TiN particles were exposed to gamma radiation at doses of 50 kGy, 200 kGy, 900 kGy and 3.5 MGy. The crystal structure of non-irradiated and irradiated samples with different doses of gamma rays was studied by X-ray diffraction method. As a result of the determination analysis of the X-ray diffraction spectra by the Rietvield method, the dependence of the lattice parameters on the radiation dose was established. The effect of gamma irradiation on the size of crystallites was determined by the Scherrer equation. The amorphization occurred in nanocrystalline TiN particles was calculated by the method of integration of diffraction peaks. It was determined that 2.5% amorphization occurred in the specified irradiation interval.

Experimental and theoretical interpretations of structural, optical, mechanical and thermal properties of 2-aminopyridinium phthalate single crystals

Nonlinear optical good quality single crystals of 2-aminopyridinium phthalate single crystals are synthesized by solution growth technique. Structural parameters are elucidated by Single Crystal X-ray diffraction method which reveals that the material crystallizes in non-centrosymmetric crystalline framework. Vibrational assignments are interpreted by Fourier Transform Infrared spectral analysis. The thermal, mechanical and laser stability are explored by TG/DTA, microhardness and Laser Damage threshold analysis. The material has good emission nature in the violet emission region. The linear optical properties are elucidated with the help of UV–visible spectral analysis. The intermolecular charge transfer interactions are analyzed by HOMO-LUMO and MESP maps by using Gaussian ’09 software program. The second harmonic generation efficiency of the synthesized material are predicted by Kurtz Perry powder technique.

Surface Plasmon Resonance Enhanced Photoelectrochemical Sensing of Cysteine Based on Au Nanoparticle-Decorated ZnO@graphene Quantum Dots.

In this work, Au nanoparticle-decorated ZnO@graphene core-shell quantum dots (Au-ZnO@graphene QDs) were successfully prepared and firstly used to modify an ITO electrode for the construction of a novel photoelectrochemical biosensor (Au-ZnO@graphene QDs/ITO). Characterization of the prepared nanomaterials was conducted using transmission electron microscopy, steady-state fluorescence spectroscopy and the X-ray diffraction method. The results indicated that the synthesized ternary nanomaterials displayed excellent photoelectrochemical performance, which was much better than that of ZnO@graphene QDs and pristine ZnO quantum dots. The graphene and ZnO quantum dots formed an effective interfacial electric field, enhancing photogenerated electron-hole pairs separation and leading to a remarkable improvement in the photoelectrochemical performance of ZnO@graphene QDs. The strong surface plasmon resonance effect achieved by directly attaching Au nanoparticles to ZnO@graphene QDs led to a notable increase in the photocurrent response through electrochemical field effect amplification. Based on the specifical recognition between cysteine and Au-ZnO@graphene QDs/ITO through the specificity of Au-S bonds, a light-driven photoelectrochemical sensor was fabricated for cysteine detection. The novel photoelectrochemical biosensor exhibited outstanding analytical capabilities in detecting cysteine with an extremely low detection limit of 8.9 nM and excellent selectivity. Hence, the Au-ZnO@graphene QDs is a promising candidate as a novel advanced photosensitive material in the field of photoelectrochemical biosensing.