Zinc Oxide Core Research Articles

PROTOTYPE OF Ag@ZnO CORE SHELL FOR THE STERILIZATION OF MURAL PAINTINGS

Cultural heritage sites often experience the unfavorable alteration of biodeterioration of mural paintings and wall inscriptions. Controlling or preventing biodegradation that may occur has been achieved through the use of various treatment methods, such as physical, chemical, and environmental control procedures. Regrettably, these treatments are often highly toxic to the health of conservators and visitors. Moreover, it causes pigmentation, is expensive, has low long-term results, and has poor long-term effectiveness. The use of Ag@ZnO core shell prototype in the field of cultural heritage was the first time in this research. The application was made to a painted wall inscription that dates back to the Middle Kingdom of ancient Egypt. A one-step chemical method was used to synthesize Ag@ZnO and it was examined using XRD, TEM, BET surface area, and Raman. These tests proved that the silver's core shell covered the zinc oxide's core and confirmed its purity. The painting on the wall was analyzed by SEN-EDX, Raman, and XRD analysis, and it was determined that the stone was limestone, the pigments were (Carbon for black pigment, Hematite for a red pigment, and Egyptian blue for blue pigment). These pigments and animal glue were combined to create the binding medium. The painted wall inscription was treated with Ag@ZnO treatments using a spray technique with a 5% concentration. The spectrophotometer was used to confirm that the color change has been below 5. This treatment method is non-hazardous, can be utilized both in vivo and in vitro, and does not necessitate the required environmental atmosphere or UV index.

The significant role of CNT-ZnO core-shell nanostructures in the development of FDM-based 3D-printed triboelectric nanogenerators

A recent innovation in energy resource consumption has propelled the implementation of a green energy source in the form of triboelectric nanogenerators (TENGs). The combination of 3D printing with TENG has generated larger ripples in the field of energy storage and distributed power supply technology. The current research focusses on developing fused deposition modeling (FDM)-based TENG devices using feedstock materials such as polylactic acid (PLA) and acrylonitrile butadiene styrene as tribopositive and tribonegative layers, respectively. This study emphasizes on the role of carbon nanotube-zinc oxide (ZnO) core-shell nanostructures reinforced into PLA by examining their impact on the final TENG output voltage. The presence of carbon nanotube -zinc oxide core shell (CNS) has enhanced the TENG output voltage (Voc) from 1 V to 8 V. Furthermore, FDM 3D printing parameters such as filling rate (%), layer thickness, and printing patterns have engaging influence on Voc. Our research identifies PLA/CNS layers comprising 20% filling rate as having a layer thickness of 0.1 mm, and a donut pattern obtaining the highest Voc (8.9 V). The reinforcement of CNS into PLA has also augmented its comprehensive properties including tensile strength and electrical conductivity. This research paves a path towards innovative fabrication strategies for TENG devices towards next generation portable electronic devices using FDM 3D printers.

Synthesis of Au/ZnO nanocomposite and Au:ZnO core:shell via laser ablation for of photo-catalytic applications

ABSTRACT The pulsed laser ablation technique is a safe and eco-friendly method, this technique was used to prepare gold (Au) and zinc oxide (ZnO) in two forms, both as core:shell nanoparticles (CS NPs) and a nanocomposite (NC). The absorption behaviour for Au/ZnO NCs and Au:ZnO CS NPs was investigated the UV-visible of Au NPs peak at 525 nm whiles the peak of the ZnO NPs at 375 nm. Transmission electron microscope (TEM) images show the average size of Au NPs is 30–45 nm adhering to ZnO NPs with an average size of 55–60 nm. In Au/ZnO CSNPs, Au acts as a core while the ZnO nanoparticles produced a shell; in spherical gold nanoparticles, the average shell thickness of ZnO is 10–15 nm. As synthesised, the Au:ZnO CSNPs are endowed with high photocatalytic activity even after multiple cycles of photo-catalytic reactions when compared with Au/ZnO NCs.

Cur-loaded magnetic ZnFe2O4@mZnO-Ox-p-g-C3N4 composites as dual pH- and ultrasound responsive nano-carriers for controlled and targeted cancer chemotherapy

Curcumin (Cur)-loaded zinc ferrite-mesoporous (m) zinc oxide core–shell -oxygen functional groups (carboxyl, carbonyl and hydroxyl) rich mesoporous (p) graphitic (g) carbon nitride (ZnFe2O4@mZnO-Ox-p-g-C3N4) carriers were designed as a potential magnetic drug delivery carrier with pH and ultrasound sensitivity for targeted drug delivery. Application of focused ultrasound can be an effective stimulant for highlighting tumor tissue or activatng delivery of echogenic drugs, which is expected to lower the systemic side effects of chemotherapy. The mixed application of physical/external (ultrasound) and chemical/internal (pH) triggers can allow for targeted release of Cur at chosen sections of tumor tissue. ZnFe2O4@mZnO and ZnFe2O4@mZnO-p-g-C3N4 nano-carriers were characterized using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Fourier rransform infra-red (FTIR) spectroscopy, dynamic light scattering (DLS), zeta potential analysis, transmission electron microscopy (TEM), BET (Brunauer–Emmett–Teller), vibrating sample magnetometery (VSM), thermogravimetric analysis (TGA) and in vitro cytotoxicity assays. The ZnFe2O4@mZnOand ZnFe2O4@mZnO-Ox-p-g-C3N4 magnetic nano-carriers showed high loading efficiency of 51.39 and 67.37%, respectively, were stable in water for 24 h. The carriers Nano-carriersshowed pH- and ultrasound-sesnsitive release of Cur. The release at pH = 5.5 for (ZnFe2O4@mZnO 70.28%) (ZnFe2O4@mZnO-Ox-p-g-C3N4 56.05%) was more than that at pH = 7.4 for (ZnFe2O4@mZnO 66.26%) (ZnFe2O4@mZnO-Ox-p-g-C3N4 45.40%) after 72 h.

Superior discharged energy density in polyetherimide composites enabled by ultra-low ZnO@BN core-shell fillers

The primary strategy to increase dielectric constant and energy storage density is adding a high fraction of fillers with high dielectric constant to polymer matrix. Yet, it has not been very successful without encountering processing difficulties, lowered breakdown strength, and mechanical inflexibility. Herein, we introduce an unconventional approach using ultra-low fraction of zinc oxide core and boron nitride shell (ZnO@BN) filler with very high thermal conductivity dispersed in polyetherimide (PEI) for the same purpose. For the 0.1 vol% core-shelled fillers, the PEI composite film exhibits a superior dischargeable energy density of 10.8 J/cm3 and a high efficiency of 92.1% at an electric field of 500 kV/mm. The polarization responses under high electric fields and simulation reveal the association with the increased interfacial polarization of the thermally conductive core-shelled structure. This strategy lays out a new route to further investigate of high energy density composite and capacitor technologies.

Graphene Oxide Coated Zinc Oxide Core–Shell Nanofibers for Enhanced Photocatalytic Performance and Durability

Recently, heterogeneous structured semiconductor photocatalysts have received significant interest in promoting global cleaning from the environmental pollution. Herein, we report the synthesis of graphene oxide (GO) wrapped zinc oxide (ZnO) core–shell nanofibers (ZnO@G CSNFs) by the simple core–shell electrospinning and subsequent annealing for efficient photocatalytic performance and stability. The heterostructured catalyst consisted of ZnO forming an enclosed core part while the GO was positioned on the surface, serving as a protective shell. Field emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction were used to confirm the synthesis of the desired product. Enhanced photocatalytic activity ZnO@G CSNFs was found compared to the corresponding ZnO NFs. Similarly, incorporation of GO into the ZnO nanofiber in a core–shell format significantly suppressed the photocorrosion. This study highlights the usefulness of using GO as the coating material to boost the photocatalytic performance of ZnO-based photocatalysts.

Enhanced Performance of White Light Generation from ZnS/ZnO Core/Shell Nanocrystals

Zinc sulfide (ZnS) and zinc oxide (ZnO) nanocrystals (NCs) were synthesized to arrangement the ZnS / ZnO core / shell NCs via chemical reaction afterward produced from nanocomposite. The modified development of ZnS / ZnO NCs and the sulfurization and oxidation ecosystems could detect many external appearance and colors. Photoluminescence (PL) was analyzed to determine the properties and optical features of such nanostructures, as well as the energy gap between chemical bands. In addition, material characterizations verified, take in electron microscopy scanning and X-ray diffraction a first rising ZnS/ZnO core / shell nanocrystals. An absorption spectrum of ZnO shells on ZnS cores NCs was limited to development technique. The prepared nanocomposites seemed to have the results of scanning electron microscopy (SEM) and uniform in size limited within 3-4 nm radius. The core / shell nanocomposites ZnS / ZnO NCs are capable of generating white light uses. The white light emission was accomplished by illumination the UV-LED (GaN) nanocomposites of the core ZnS and ZnO cover NC.

Core-shell nanostructured ZnO@CoS arrays as advanced electrode materials for high-performance supercapacitors

Cost-effective zinc oxide (ZnO) nanomaterials with high theoretical specific capacity have been regarded as one of the most prospective candidates for high-performance supercapacitor; however, its extensive application is limited by poor active sites and low conductivity, which increase the internal resistance of the electrode and reduce the capacity of the supercapacitor. Herein, we carried out a simple two-step method to synthesize a core-shell structure of ZnO core nanosheets enclosed in a shell of CoS (ZnO@CoS). This well-designed structure improves the electrical conductivity of the electrode, and the large specific surface area provides sufficient active sites. The as-prepared ZnO@CoS electrode exhibits a high specific capacity of 898.9 C g−1 at a current density of 3 mA cm−2, which is 1.47 and 1.70 times higher than those of ZnO and ZnO precursor. Moreover, the assembled asymmetric supercapacitor (ASC) with active carbon (AC) as the negative electrode and ZnO@CoS as the positive electrode displays an energy density of 45.2 Wh kg−1 at a power density of 1039.1 W kg−1 as well as achieves excellent specific capacity of 2438 mC cm−2. The ASC also shows superior cycleability with 107% capacity retention after 11,000 cycles.

Co-delivery of doxorubicin and DNAzyme using ZnO@polydopamine core-shell nanocomposites for chemo/gene/photothermal therapy

Multi-modal nanomedicines that synergistically combine chemo-, gene-, and photothermal therapy have shown great potential for cancer treatment. In this study, a core-shell nanosystem-based on a zinc oxide (ZnO) nanocore and a polydopamine (PDA) shell was constructed to integrate chemo- (doxorubicin, DOX), gene- (DNAzyme, DZ), and photothermal (PDA layer) therapy in one system. Instead of small interfering RNAs, we employed DZ for tumor-related gene (survivin) regulation owing to its higher stability, biocompatibility, and predictable activity. DOX and amino-modified DZ were loaded onto the PDA shell via physisorption and covalent conjugation, respectively. Specifically, the ZnO nanocore was designed as a metal cofactor reservoir to release Zn2+ in response to intracellular stimuli, which triggered the activation of DZ for gene silencing after endocytosis into cells. Both in vitro and in vivo experiments demonstrated the enhanced anti-tumor efficacy of these multifunctional nanocomposites and highlighted the advantages of these nano-drug delivery systems to alleviate the side effects of DOX. This study provides a strategy for synergistic cancer therapy via chemo/gene/photothermal combination and offers a strategy to harness DZ as a gene-silencing tool for disease treatment in combination with other therapeutic modalities. Statement of SignificanceIn this work, we constructed a core-shell nanosystem containing a zinc oxide (ZnO) nanocore and a polydopamine (PDA) outer layer, which integrated chemo- (doxorubicin, DOX), gene- (DNAzyme, DZ), and photothermal (PDA layer) therapies for multimodal cancer therapy. Specifically, the ZnO core was incorporated to solve the key issue of DZ for gene silencing applications, which acted as the metal cofactor reservoir to release Zn2+ inside cells for effective DZ activation. In addition, the PDA shell could detoxify the ZnO by scavenging the reactive oxygen species produced by ZnO, thus increasing the biocompatibility of the nanocarrier. This work solves the key issue of DZ for RNAi-based applications, offers a platform to combine DZ with other therapeutic modalities, and also provides a smart strategy to achieve triggered activation of biocatalytic reactions for therapeutic applications.

A Bio-Conjugation Chemistry Strategy to Self-Immobilize Antibodies with ZIF-90-ZnO-MoS2 Nanohybrid for Exosome Markers Analysis

Motivation Cell signaling proteins have been widely regarded as some of the most powerful biomarkers for cancer diagnosis because they are real therapy related molecules. Extracellular vesicles, exosomes, transport proteins to promote tumor growth and are stable in biofluids at room temperature.[1] Hence, detection of exosomal proteins (e.g., cluster of differentiation (CD) 9, CD 63, CD 81) would be easily deployed at the point-of-care (POC) diagnostic. A successful electrochemical biosensor is generally determined by electrodes and their modification as well as specific bio-recognition elements (BREs).Graphene like MoS2 has emerged in biosensing applications owing to their intriguing properties, such as good catalytic properties, interesting metallic-to-semiconducting transition from 1T to 2H phase, and good biocompatibility.[2] However, a particularly vexing problem for MoS2 as the sensing materials is the structural instability that the exfoliated or ultrathin two dimensional (2D) MoS2 is hard to be retained in in their freestanding state. The surface modification technologies, such as growth of building blocks could transfer the 2D to relatively stable 3D nanoarchitectures, in which each component can also exert different function.Herein, we demonstrate a nanostructure consisting of zinc oxide (ZnO) nanowires (NWs) array grown on 2D MoS2forming a new nanoarchitecture (ZnO-MoS2) providing high specific surface area and good electron transport capability. Then, zeolitic imidazolate framework 90 (ZIF-90) thin films are in-situ deposited onto ZnO NWs by using ZnO as precursor to directly react with imidazole-2-carboxyaldehyde (ICA). The integrated hybrid nanostructure, denoted as ZIF-90-ZnO-MoS2, possesses not only effective mass transport and electron transduction capabilities but also covalent bio-conjugation of BREs through the aldehyde group on the bridging ICA ligand in ZIF-90. Of particular note is the ZnO NWs array is an indispensable part of the hybrid nanostructure, since the in-situ growth of ZIF-90 and effective integration with layered MoS2 is still a challenge. Through the cooperation of three different kinds of building blocks, from signal generation, amplification to transduction could be achieved in an integrated nanoarchecture. Results and Discussion Figure 1a displays the scanning electron microscope (SEM) image of obtained ZIF-90-ZnO-MoS2 nanohybrid, from which the ordered NWs array is uniformly grown onto 2D MoS2 material. The higher magnification SEM (Figure 1b) and transmission electron microscopy (TEM) (Figure 1c) images show that the length and diameter of vertical ZnO NWs are 1.5 μm and 50 nm, respectively. Further high resolution TEM (HR-TEM) (Figure 1d) characterization demonstrates that the NWs are consisted of highly crystal ZnO core with the diameter of about 25 nm and ZIF-90 sheath with the thickness of about 12 nm.A FITC-labeled goat anti-human immunoglobulin G (IgG) is employed to verify our hypothesis. The inset of Figure 1e shows the fluorescence microscopy image of microelectrode immobilized with FITC-labeled goat anti-human IgG. It can be seen that only the region deposited with ZIF-90-ZnO-MoS2 nanohybrid visualizes green fluorescence. This result illustrates ZIF-90-ZnO-MoS2 nanohybrid possesses the capability of direct covalent bio-conjugation of antibody. And the results shown Figure 1e further confirm the developed hybrid material could effectively detect signaling protein.We next fabricated a microfluidic electrochemical microsensor chip, and the configuration is shown in Figure 1f. The microsensor chip is composed of a polydimethylsiloxane (PDMS) layer sealed with screen-printed electrodes. The microsensor is consisted of five electrodes, including counter electrode (CE), reference electrode (RE) and three different working electrodes. Among the three working electrodes, electrode 1 and 2 are locally deposited with fabricated ZIF-90-ZnO-MoS2 nanohybrid material as the test electrodes, and electrode 3 is printed with carbon conductive ink for the background signal deduction. The micro-channels on the chip are employed for the simultaneous immobilization of bio-recognition antibodies as well as dual detection of exosome markers (CD63 and CD9). From Figure 1g, our fabricated microsensor chip shows obvious response towards NCI-H 1650, and almost no signal for other cells supernatant (NCI-H 1650: human non-small cell lung cancer cells, 16 HBE: human bronchial epithelial cells, HFL-1: human fetal lung fibroblast-1 and HUVEC: human umbilical vein endothelial cells). Conclusion In summary, the ZIF-90-ZnO-MoS2 nanohybrid integrated with different kinds of building blocks realizes the cooperation of multi-function, including covalent bio-conjugation of antibodies, signal generation and transduction. To further combine with microfluidic electrochemical microsensor chip, the simultaneous immobilization of bio-recognition antibodies and dual detection of exosome markers can also be acquired.

Narrow range of zinc oxide core–shell hollow microspheres dopings for mechanical tensile promotion of 110KBPSCCO superconductor

Although substitutions on copper sites always inhibit superconducting properties, the present investigations were successfully promoted mechanical tensile averages for HTc-2223- BPSCCO superconductor with general formula BiPbSr2Ca2Cu3-x(Zn)xO10±δ where x = 0.02, 0.04,0.08 and 0.16 mol respectively in the investigated range without damaging its superconducting features. The study is focusing on the effect of core-shell zinc ions hollow microspheres dopings (x) on the copper sites, where 0 ≤ x ≤ 0.16 mol on the superconducting, mechanical tensile features of 110K-2223-BPSCCO superconductor. The structural and micro-structural features of pure and core shell Zn-doped BPSCCO superconductors samples were carefully investigated by x-ray diffraction (XRD) and scanning electron microscope (SEM). Mechanical tensile measurement indicated that doping ratio (x) with ~0.08 mol is the optimum doping ratio from core shell hollow zinc microspheres achieving maximum tensile average of 51.2 MPa with stroke~0.323 mm acheiving promotion ratio~63.57% in contrast with mechanical tensile measured for pure 2223- BPSCCO superconductor (31.3 MPa with stroke~0.172 mm).

Evaluation of anticorrosive behaviour of ZnO nanotetra-pods on a AZ91-grade Mg alloy

Highly cross-linked zinc oxide (ZnO) with the nanorod morphology of tetra-pods was successfully prepared using a microwave irradiation (MWI) technique. In comparison with the available conventional techniques, the MWI technique has the advantage of producing different morphological structures with high purity and in a shorter reaction time. These tetra-pods consist of a ZnO core in the zinc blende from which four ZnO arms emerge in the wurtzite structure. In this investigation, the effects of irradiation times and the growth mechanism of ZnO nanotetra-pods were discussed. The structural, morphological and optical properties of ZnO nanorods were investigated by field emission scanning electron microscopy, X-ray diffraction, an ultra violet visible spectrometry and energy-dispersive spectroscopy. The electrochemical corrosion behaviours of an AZ91-grade Mg alloy and a ZnO/PN nanotetra-pod-coated Mg alloy were investigated. The Tafel plot revealed that the corrosion of Mg drastically decreased on coating with a thin layer of ZnO nanotetra-pods and PN (Mg/PN/ZnO) compared to Mg in a KOH electrolyte.

Characterization of ZnO Nanoparticles using Superconducting Tunnel Junction Cryodetection Mass Spectrometry.

Zinc oxide (ZnO) nanoparticles coated with either n-octylamine (OA) or α-amino poly(styrene-co-acrylonitrile) (PSAN) ligands (L) have been analyzed using laser desorption/ionization and matrix assisted laser desorption/ionization (MALDI) time-of-flight (TOF) superconducting tunnel junction (STJ) cryodetection mass spectrometry. STJ cryodetection has the advantage of high m/z detection and allows for the determination of average molecular weights and dispersities for 500-600 kDa ZnO-L nanoparticles. The ability to detect the relative energies deposited into the STJs has allowed for investigation of ZnO-L metastable fragmentation. ZnO-L precursor ions gain enough internal energy during the MALDI process to undergo metastable fragmentation in the flight tube. These fragments produced a lower energy peak, which was assigned as ligand-stripped ZnO cores whereas the individual ligands were at too low of an energy to be observed. From these STJ energy resolved peaks, the average weight percentage of inorganic material making up the nanoparticle was determined, where ZnO-OA and ZnO-PSAN nanoparticles are comprised of ~62% and ~68% wt ZnO, respectively. In one example, grafting densities were calculated based on the metastable fragmentation of ligands from the core to be 16 and 1.1 nm-2 for ZnO-OA and ZnO-PSAN, respectively, and compared with values determined by thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Graphical Abstract ᅟ.

(Invited) Tailoring Zinc Oxide Nanorod-Arrays for Photo-(electro)Chemical Applications

As one of the most studied metal-oxides Zinc Oxide (ZnO) already found its way into many industrial applications. Nevertheless enormous research interest is drawn to this earth-abundant, environmentally-friendly material as it offers interesting material properties such as a high exciton binding energy, a direct bandgap and comparably high charge carrier mobility.1 Furthermore the ability to grow ZnO nanostructures using a wide range of deposition techniques offers new perspectives for the material to be used in opto-electronics.2 Low-temperature solution based methods are of particular interest as possible routes to the low-cost growth of high surface-area nanostructures for the integration of ZnO into novel energy production and storage devices.3 The steadily growing research areas of solar water splitting and photo-catalysis are prominent examples of areas where interest in ZnO-based materials and devices may be found.4-6 For these applications the semiconductor/electrolyte interface plays a crucial role. It is of the highest importance to carefully engineer the materials properties in order ensure effective charge carrier transport across the interface. In turn it must be the goal of materials research to tailor the ZnO towards these target applications, where possible addressing the key issues of short timescale charge carrier recombination over intrinsic defects, low-visible light absorption and photo-corrosion. This paper describes strategies for the minimisation of the undesirable influences associated with these issues for ZnO nanorod-arrays grown from solution. Firstly it is demonstrated that careful defect-engineering can be used to increase the probability to run photo-(electro)chemical reactions. Here, the specific focus is directed towards orange-luminescent defect-centres. Linear sweep voltammetry in neutral electrolyte solution reveals that ZnO nanorod-arrays exhibiting strong orange emission show a defect-promoted increase in photo-current of ca. 200 % under simulated sunlight as compared to as-grown nanorod-arrays. As the large bandgap energy of ZnO, some 3.3 eV (< 380 nm), considerably limits the absorption of sunlight a doping strategy is applied in order to shift the materials absorption into the visible region. It is demonstrated that this may be achieved by the incorporation of significant amounts of cobalt into the ZnO host lattice using a newly developed low-temperature solution-based growth method. It is shown that the visible-light absorption of the resulting material, which consists of ZnO:Co nanorod-arrays directly deposited onto seed-layer coated glass substrates, extends up to 700 nm by controlling the cobalt concentration in the growth solution. Lastly, we address the issue of photocorrosion of ZnO-based photo-electrodes. Previously various attempts have been made to enhance the material`s chemical stability. Over-coating of ZnO with thin layers of e.g. C3N4 or TiO2 using different deposition techniques are among the most applied strategies.7-9 In order to produce effective and stable chemical barriers pin-hole free layers are essential. atomic layer deposition (ALD) offers the advantage of controlled and nominally pin-hole free deposition of ultrathin barrier layers even onto 3D-geometries, thus, making it potentially a powerful technique for the chemical stabilisation of ZnO nanostructures for photo-(electro)chemical applications. In this study the ZnO nanorod-arrays are over-coated with ultrathin ALD TiO2 layers. It is presented that TiO2 shells are able to chemically protect the ZnO core in acidic media. However, it was found that for some samples the TiO2 barriers are not complete – especially at the rod tips - leading to a considerably lower etch rate as compared to uncoated nanorod-arrays. Photo-electrochemically the core-shell structures show a photo-current stabilisation for several hours. Nevertheless the initial photo-current is lower when compared to uncoated nanorod-arrays indicating a higher charge transfer resistance for the ZnO-TiO2/electrolyte interface. Acknowledgements: This work was funded by Science Foundation Ireland, US: Ireland Grant RENEW- Research into Emerging Nanostructured Electrodes for the Splitting of Water, number 13/US/I2543. 1. H. Morkoç and Ü. Özgür, in Zinc Oxide - Fundamentals, Materials and Device Technology, Wiley-VCH Verlag GmbH & Co. KGaA, 2009, pp. 131-244. 2. A. B. Djurišić et al., Progress in Quantum Electronics, 2010, 34, 191-259. 3. P. S. Xu et al., Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003, 199, 286-290. 4. Y. Lu et al., Nano Research, 2011, 4, 1144-1152. 5. Y. Mao et al., Nano Energy, 2014, 6, 10-18. 6. L. Cai et al., International Journal of Hydrogen Energy, 2015, 40, 1394-1401. 7. R. T. Sapkal et al., Journal of photochemistry and photobiology. B, Biology, 2012, 110, 15-21. 8. Y. Wang et al., Energy & Environmental Science, 2011, 4, 2922. 9. M. Liu et al., The Journal of Physical Chemistry C, 2013, 117, 13396-13402.

A facile chemical synthesis of ZnO@multilayer graphene nanoparticles with fast charge separation and enhanced performance for application in solar energy conversion

This work reports on the in-situ chemical synthesis and their properties of multilayer graphene (MLG) shells, made by unzipping single walled carbon nanotubes (SWCNTs), on the surface of Zinc oxide (ZnO) core nanoparticles (NPs). The stable oxygen bridge bonds between the ZnO core and the oxygen-related functional groups on the MLG shells facilitate the efficient photoinduced charge separation. This charge separation mechanism is confirmed experimentally using time-correlated single photon counting (TCSPC) measurements. The calculated average carrier lifetimes of the ZnO@MLG NPs are approximately 102 times faster than those for the bare ZnO NPs. The efficient electron transfer between the ZnO core and the MLG shell resulted in the significant improvement of the photocatalytic activity and the photoelectrochemical response. Simultaneously, the photocorrosion of ZnO was prevented by having the oxygen bridge bonds between the ZnO and MLG which suppressed the photo-generated holes oxidizing the surface oxygen atoms on ZnO, and in turn the holes are consumed by photocatalytic reaction. The 4.3 times enhanced photocurrent density at 0.2V vs. Ag/AgCl (pH 6.9) and around 10 times higher rate constant value of photodegradation of rhodamine B were achieved by ZnO@MLG NPs in comparison with those of bare ZnO NPs.

Determination of Ascorbic Acid by a Gold–Zinc Oxide Nanoparticle-Modified Glassy Carbon Electrode

ABSTRACTA novel electrochemical sensing platform was developed based on flower-like gold–zinc oxide core–shell nanoparticles and a graphene nanocomposite-modified glassy carbon electrode. The gold–zinc oxide core–shell nanoflowers were synthesized by seed growth and characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and ultraviolet-visible absorption spectroscopy. The modified electrode provided good electrocatalytic properties, rapid response, high stability, and favorable reproducibility for determination of ascorbic acid. The performance of the sensor included a linear dynamic range from 1.0 × 10−7 to 6.0 × 10−4 M, a limit of detection of 3.9 × 10−8 M, and a sensitivity of 24.12 µA/mM. The nanocomposite also provided excellent selectivity and lower potential for the oxidation of ascorbic acid. The sensor was used for the determination of ascorbic acid in tablets with satisfactory results. This device provides rapid, simple, and selective determination of ascorbic acid.

The Capacity and Durability of Amorphous Silicon Nanotube Thin Film Anode for Lithium Ion Battery Applications

In this communication, we report that a silicon nanotube thin film electrode with 0.6 mg loading exhibited an initial discharge capacity of 4766 mAh g −1 and retained about 3400 mAh g −1 after 20 cycles at 100 mA g −1 rate. The silicon nanotube thin film samples with thicknesses ranging from 10‐28 microns were prepared using silicon deposition on bulk produced zinc oxide nanowire films and subsequent removal of zinc oxide cores. The developed silicon nanostructures exhibit tubular geometry with both open ends. The nanotubes with thin walls are shown to accommodate large volume changes with lithiation and exhibit stable capacity retention. The presence of hydrogenated nanocrystalline silicon (nc-Si:H) is shown to be essential for the silicon nanotube thin film performance for lithium ion battery applications. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any

Interaction of L-Cysteine with ZnO: Structure, Surface Chemistry, and Optical Properties.

Zinc oxide (ZnO) nanoparticles (NPs) were stabilized in water using the amino acid l-cysteine. A transparent dispersion was obtained with an agglomerate size on the level of the primary particles. The dispersion was characterized by dynamic light scattering (DLS), pH dependent zeta potential measurements, scanning transmission electron microscopy (STEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, photoluminescence (PL) spectroscopy, and X-ray absorption fine structure (EXAFS, XANES) spectroscopy. Cysteine acts as a source for sulfur to form a ZnS shell around the ZnO core and as a stabilizer for these core-shell NPs. A large effect on the photoluminescent properties is observed: the intensity of the defect luminescence (DL) emission decreases by more than 2 orders of magnitude, the intensity of the near band edge (NBE) emission increases by 20%, and the NBE wavelength decreases with increasing cysteine concentration corresponding to a blue shift of about 35 nm due to the Burstein-Moss effect.

The effect of operational parameters on the photocatalytic degradation of Congo red organic dye using ZnO–CdS core–shell nano-structure coated on glass by Doctor Blade method

Photocatalytic degradation of Congo red was investigated using ZnO–CdS core–shell nano-structure coated on glass by Doctor Blade method in aqueous solution under irradiation. Field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques were used for the morphological and structural characterization of ZnO–CdS core–shell nanostructures. XRD results showed diffractions of wurtzite zinc oxide core and wurtzite cadmium sulfide shell. FESEM results showed that nanoparticles are nearly hexagonal with an average diameter of about 50nm. The effect of catalyst loading, UV-light irradiation time and solution pH on photocatalytic degradation of Congo red was studied and optimized values were obtained. Results showed that the employment of efficient photocatalyst and selection of optimal operational parameters may lead to complete decolorization of dye solutions. It was found that ZnO–CdS core–shell nano-structure is more favorable for the degradation of Congo red compare to pure ZnO or pure CdS due to lower electron hole recombination. The results showed that the photocatalytic degradation rate of Congo red is enhanced with increasing the content of ZnO up to ZnO(0.2M)/CdS(0.075M) which is reached 88.0% within 100min irradiation.

Supported platinum–zinc oxide core–shell nanoparticle catalysts for methanol steam reforming

Pt@ZnO and Pd@ZnO core–shell structures have been synthesized and shown to form alloy catalysts with good CO2 selectivity for MSR.