Surface Crystallographic Structure Research Articles

Electrodeposition of Molybdenum from Water-in-Acetate Electrolytes

This paper reports a systematic study on the electrodeposition of metallic molybdenum from water-in-salt electrolytes containing superhigh concentrations of acetate. Cyclic voltammetry and DC deposition were carried out on rotating disk electrodes with various concentrations of CH3COOK and CH3COONH4 to determine the effects of NH4 + and K+ on Mo deposition. A comparison was performed between CH3COOLi, CH3COONa, and CH3COOK to study the effects of different alkali metal cations. A synergistic effect was observed between K+ and NH4 +, where Mo deposition rate is enhanced in the presence of both cations. However, such synergistic effect was not observed between NH4 + and other alkali cations. In addition, the impact of substrate on Mo deposition was also studied using Pt and Cu electrodes with different activity toward hydrogen evolution reaction. Electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to characterize the surface morphology, crystallographic structure, and metallic state of Mo in the electrodeposited films.

Structural and Mechanical Properties of Non-Glazed Ceramic Tiles Developed from Selected Mineral Deposits in Uganda

Uganda is well endowed with clay resources; however, comprehensive knowledge about the composition, structure and suitability of these clays for ceramic tile production is lacking. In this study, we provide a comprehensive characterisation of locally sourced clays in Uganda and their suitability for ceramic tile production. In the study, we developed ceramic tiles using feldspar, kaolin, ball clay and sand from four different sites in Uganda. We focused on analysing the surface morphology, crystallographic structure and mineralogical composition of the raw materials. In addition, we examined the mechanical properties of the developed tiles with the different mixture ratios of the clay types. The surface morphology of the raw materials was analysed by using a scanning electron microscope. The structural analysis of the raw clay materials was done using X-ray diffraction. The mineralogical composition of the raw materials was investigated using energy dispersive X-ray spectroscopy and X-ray fluorescence spectroscopy. The results indicated that the strength and rapture modulus are influenced by the composition of kaolin and feldspar. We concluded that the selected mineral deposits can be used in the production of ceramic tiles in Uganda.

Screening the Surface Structure-Dependent Action of a Benzotriazole Derivative on Copper Electrochemistry in a Triple-Phase Nanoscale Environment.

Copper (Cu) corrosion is a compelling problem in the automotive sector and in oil refinery and transport, where it is mainly caused by the action of acidic aqueous droplets dispersed in an oil phase. Corrosion inhibitors, such as benzotriazole (BTAH) and its derivatives, are widely used to limit such corrosion processes. The efficacy of corrosion inhibitors is expected to be dependent on the surface crystallography of metals exposed to the corrosion environment. Yet, studies of the effect of additives at the local level of the surface crystallographic structure of polycrystalline metals are challenging, particularly lacking for the triple-phase corrosion problem (metal/aqueous/oil). To address this issue, scanning electrochemical cell microscopy (SECCM), is used in an acidic nanodroplet meniscus|oil layer|polycrystalline Cu configuration to explore the grain-dependent influence of an oil soluble BTAH derivative (BTA-R) on Cu electrochemistry within the confines of a local aqueous nanoprobe. Electrochemical maps, collected in the voltammetric mode at an array of >1000 points across the Cu surface, reveal both cathodic (mainly the oxygen reduction reaction) and anodic (Cu electrooxidation) processes, of relevance to corrosion, as a function of the local crystallographic structure, deduced with co-located electron backscatter diffraction (EBSD). BTA-R is active on the whole spectrum of crystallographic orientations analyzed, but there is a complex grain-dependent action, distinct for oxygen reduction and Cu oxidation. The methodology pinpoints the surface structural motifs that facilitate corrosion-related processes and where BTA-R works most efficiently. Combined SECCM–EBSD provides a detailed screen of a spectrum of surface sites, and the results should inform future modeling studies, ultimately contributing to a better inhibitor design.

Effects of Electrolyte pH on the Electrodeposition of Nickel on Zincated Aluminium Surfaces

A nickel coating was successfully deposited on zincated aluminium by electrodeposition. A detailed study was made on the effect of the pH of electrolytes containing 0.1 M nickel sulphate (NiSO4) by cyclic voltammetry (CV). A constant potential of -0.8 V (pH 2), -1.1 V (pH 6) and -1.5V (pH 10) was chosen from different regions of each CV for the deposition of nickel using chronoamperometry (CA). The surface morphology, chemical composition and crystallographic structure of the nickel coating were investigated by field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDAX) and X-ray diffraction (XRD), respectively. The adhesion strength of the nickel coating was analysed using  Scotch® tape. It was found that the nucleation potential for nickel deposition on zincated aluminium increased with increasing electrolyte pH. Notably, pH 2 produced the highest current during the deposition of nickel as compared to pH 6 and pH 10, due to the simultaneous hydrogen evolution reaction (HER). Because of HER, a lot of pits were present on the zincated aluminium surface and only a few nickel particles were formed, as shown in FESEM images. Meanwhile, deposition using a pH 6 solution (without HER)  produced an almost fully-covered nickel coating with uniform nodular morphology. However, when the pH 10 solution was used, the coating morphology appeared as cauliflower-like agglomerates with less surface coverage. EDAX analysis showed that the nickel coating deposited at pH 6 had the highest nickel content with 73.63 wt%. XRD analysis indicated that all nickel deposits had a cubic crystalline structure. Nickel deposited with the pH 6 solution was the most well-adhered coating. Thus, electrolyte pH has a strong influence on the deposition of nickel on a zincated aluminium surface.  

Effect of growth parameters on defect structure and optical properties of ultrathin SnO2 films

Tin oxide films with thicknesses in the range from 5 to 110 nm have been deposited by reactive dc magnetron sputtering of Sn in Ar + O plasma at a low working pressure of 1.0× 10 −3 Torr on glass substrates at different temperatures (150–400 °C). The effect of deposition time, substrate temperature, and oxygen partial pressure on surface morphology , crystallographic structure, optical properties, and photoluminescence characteristics of SnO 2 films has been studied and correlated with their defect structure . The structural transformation from nanocrystalline to polycrystalline of thicker films >40 nm and films were grown at higher temperature is explained based on adatom mobility and uniform substrate coverage. Based on photoluminescence characteristics and transmittance spectra, the 20 nm thick film exhibits the least defect structure and best electronic and optical behaviors. • Ultrathin SnO 2 films (5–20 nm) are successfully grown by DC reactive sputtering. • Effect of scaling down film thickness (down to 5 nm) on physical properties. • Correlation between defect structure and optical properties. • Thinner films are much smoother than the thicker films. • Low structural defect concentration found in 10–40 nm films.

Growth of flat-topped, mound-shaped grains with voids when depositing silver thin films at high substrate temperatures using direct-current magnetron sputtering

Thin films of silver were deposited on nonalkali glass substrates at substrate temperatures ranging from room temperature (28 °C) to 150, 200, 300, 400, and 500 °C at discharge pressures of 0.40, 1.20, and 2.00 Pa using direct current magnetron sputtering. On the basis of the measured cross-sectional and surface morphologies, crystallographic structures, and film properties, I discuss the dependence of the film structure and properties on the substrate temperature. The x-ray diffraction measurements showed that the <111> orientation was preferred for all deposition conditions. Scanning electron microscope observations revealed a microstructure of convex-shaped fine grains for a substrate at room temperature, while laterally growing, mound-shaped grains with flat-topped surfaces appeared at substrate temperatures of 400 and 500 °C. Atomic force microscopy also showed an increase in the lateral size and height of the mound-shaped structures with increasing substrate temperature. The lateral grain size evaluated from the areal particle density obtained from atomic force microscopy increased significantly with increasing substrate temperature, reaching 600–800 nm at a substrate temperature of 500 °C. The film stress also changed from compressive to tensile with increasing substrate temperature. The relative density, defined as the ratio of the deposited amount-of-substance to the physical-thickness, decreased significantly with increasing substrate temperature and, at a substrate temperature of 500 °C, was approximately 0.6 times as large as that obtained for thin films deposited at room temperature. The high surface diffusivity of the Ag adatoms induces the growth of laterally growing, mound-shaped grains. Besides, the energy accumulated in the thin films during sputter deposition induces the void formation to increase the efficiency of energy release in the form of heat.

Development of a barium-modified zeolite catalyst for biodiesel production from waste frying oil: Process optimization by design of experiment

A barium-modified zeolite (Ba-ZEL) catalyst was developed via co-precipitation technique followed by thermal treatment (calcination) at different temperatures (600, 700 and 800 °C). The thermal stability, elemental composition, surface functional groups, crystallographic structure, textural characteristics, basic strength and surface morphology of the Ba-ZEL catalyst were determined using TGA/DTA, EDX, FTIR, XRD, BET, CO2-TPD and SEM techniques, respectively. The biodiesel production process conditions, such as catalyst loading, alcohol to oil ratio, temperature and time, were optimized using a central composite design approach. The Ba-ZEL composite calcined at 700 °C was selected as a representative catalyst due to its high activity for the waste frying oil (WFO) conversion, resulting in a maximum biodiesel yield of 93.17 ± 0.02% under optimum conditions (3.0 wt% catalyst loading, 12:1 methanol to WFO ratio, 65.38 °C reaction temperature and 2 h reaction time). The produced biodiesel, which was characterized by the FTIR and GC-FID analyses, contained sufficient ester groups and was in accordance with the specifications of EN 14214. Additionally, its physicochemical properties met ASTM D6751 specifications. Moreover, the Ba-ZEL700 catalyst was reused for five cycles upon regeneration using n-hexane washing followed by reactivation at 110 °C for 12 h.

Deuterium-Grown Highly-Oriented Boron-Doped Diamond Electrodes

Boron-doped diamond (BDD) have attracted increasing attention as a material for electrochemical sensors and biosensors due to its remarkable properties such as its chemical inertness, wide electrochemical potential window, low background current and biocompatibility. Diamond layers are synthesized mainly from a gas phase consisting of carbon, hydrogen, and a dopant source by microwave plasma-assisted chemical vapour deposition (MPACVD). The gas composition during the growth of diamond film has a significant influence on its surface morphology, crystallographic structure, dopant concentration, and superficial non-diamond carbon phases. Thus, the growth conditions of the diamond layer affect the electrochemical properties of the material.Herein we demonstrate the electrochemical and physicochemical studies of as-grown boron-doped diamond thin-film electrodes, synthesized in a deuterium-rich plasma (BDDD). It is the first report concerning the study of the effect of replacing hydrogen by deuterium during BDD growth. The substitution of hydrogen to deuterium in the gas phase is primarily responsible for the enhanced boron doping and significantly decrease of nondiamond sp2 phase in diamond films. Moreover, the crystallographic structure of BDDD layer is dominated by the (111) configuration while the texture of the BDDH electrode film is oriented along the (220) direction [1].The proposed boron-doped diamonds synthesized in the deuterium-rich plasma electrodes were revealed to have a higher activity towards [Fe(CN)6]3-/4- and [Ru(NH3)6]2+/3+ redox mediators than BDD electrode grown in hydrogen-rich plasma (BDDH). The peak-to-peak separation recorded on BDDD electrode reaches 60.6 mV, and 59.8 mV in [Fe(CN)6]3-/4- and [Ru(NH3)6]2+/3+ redox couples, respectively. Moreover, in Ru(NH3)6 2+/3+ solution, the apparent heterogeneous electron transfer rate constant k° app for the BDDD was equal to 5.84·10-3 cm s-1. The BDDD and BDDH electrodes were also used as an electrochemical sensor for the paracetamol detection. BDDD electrode exhibits better sensing performance towards PCM comparing to BDDH electrode. The value of limit of detectionfor the BDDD electrode was 765 nM, whereas for the BDDH was 2510 nM. The better electrocatalytic behavior of the BDDD electrodes may result from the higher amount of electroactive zones on deuterium-terminated diamond strictly related to (111) crystal facets.AcknowledgementThis work was supported by the Polish National Science Centre [2020/01/0/ST7/00104]. The DS funds of the Faculty of Electronics, Telecommunications, and Informatics of the Gdansk University of Technology are also acknowledged.Reference:[1] A. Dettlaff et al., Carbon [In press]. Doi: doi.org/10.1016/j.carbon.2020.11.096.

Fabrication of carbon cloth supported Ni@Fe double hydroxide based electrode for flexible supercapacitor applications

Herein, we have decorated the nickel-iron hydroxide (Ni@Fe LDH) directly on the carbon cloth (CC) to fabricate a flexible and binder-free electrode for electrochemical applications. The samples produced were characterized by versatile physical techniques to investigate the surface area, crystallographic structure, chemical composition, and morphology. The Ni@Fe LDH/CC electrode exhibited the high gravimetric capacitance (Cg) of 984 Fg-1 at 1 Ag-1 that is the result of the synergistic effect of hybrid composition, higher surface area, porous structure, and binder-free design. The fabricated electrode showed astonishing cyclic stability, as it retains nearly 87.6% of the initial capacity after 7000 consecutive galvanostatic charge-discharge (GCD) experiments. The best experimental cyclic activity is accredited to the flexible substrate, layered morphology, and porous architecture of the fabricated electrode that protects it from the expected pulverization and expansion processes. Additionally, our flexible and binder-free electrode showed excellent rate-performance and lost just 13.5% gravimetric capacitance when the applied current density value is changed from 1 to 9 Ag-1. In fact, numerous voids and pores of the Ni@Fe LDH sample act as ion-reservoirs and facilitate mass transport even at the higher current density. The electrochemical results ensure that our flexible electrode, thanks to its integrated capacitive performance, has the potential for practical applications in flexible energy storage systems.

The Behavior of Gold Metallized AlN/Si- and AlN/Glass-Based SAW Structures as Temperature Sensors.

Thin AlN piezoelectric layers have been deposited on high resistivity Si and glass substrates by reactive RF magnetron sputtering, in order to manufacture one-port gigahertz operating surface acoustic wave (SAW)-type resonators to be used as temperature sensors. The growth morphology surface topography, crystallographic structure, and crystalline quality of the AlN layers have been analyzed. Advanced nanolithographic techniques have been used to manufacture structures having interdigitated transducers with fingers and finger interdigit spacing width in the range of 250-170 nm. High resonance frequency ensures the increase of the sensitivity, but also of its normalized value, the temperature coefficient of frequency (TCF). The resonance frequency shift versus temperature has been measured in the -267°C-+150°C temperature range, using a cryostat setup adapted for on wafer microwave measurements up to 50 GHz. The sensitivity and the TCF were determined in the 25 °C-150 °C temperature range.

A systematic study on chemically deposited cadmium sulfide (CdS) thin film

In this work, the conventional chemical bath deposition (CBD) technique and its growth parameters were systematically studied to deposit CdS thin films on the glass substrate. The samples were prepared using a simple aqueous solution containing cadmium sulfate (CdSO4·8H2O), thiourea [SC(NH2)2], ammonium sulfate [(NH4)2SO4] as a source of cadmium, sulfur, and a complexing agent, respectively. The deposited films were characterized to study the surface morphology, crystallographic structure, chemical composition, optical and electrical properties. Through this study, the structure was determined to cubic with (111) preferential orientation and the crystallinity of the films was improved with the increase of film thickness. The transmission spectra were recorded in the range of wavelength 300–600 nm. The optical bandgap of the optimized CdS films was varied from 2.43 to 2.74 eV. All the films exhibit n-type of conductivity which was found in the order of 10–4 to 10–5 (1/Ω-cm), suggesting that it would be suitable for the buffer layer in thin-film solar cells.

Microstructure and Properties of Co-Ni-Cr<sub>3</sub>C<sub>2</sub> Nanocomposite Coatings Produced by Jet-Electrodeposition

Co-Ni-Cr3C2 nano-composite coatings at various concentrations of Cr3C2 particles were produced by Jet-eletrodeposition. Surface morphology and crystallographic structure of the coatings were investigated by means of SEM and XRD. Mechanical properties of the coatings were determined using Vickers microhardness and friction wear tester. It was found that adding nano-Cr3C2 concentration in electroplating bath weakens the abnormal co-deposition to a certain extent and decreases the deposition amount of co. The increase of the content of nano-Cr3C2 in the bath, the content of nano-Cr3C2 in the coating increases, when the content of nanoparticles is 80g/l, the content of nano-chromium carbide in the coating reaches the maximum value of 25.13 wt.%. With the addition of nano-Cr3C2 particles, the surface of nanocomposite coating is uneven and presents cauliflower head morphology. When the content of nano-Cr3C2 particles is 40g/l, the growth of the coating is the most uniform and compact. The phase structure of Co–Ni/nano-Cr3C2 coatings is not changed by the codeposition of nano-Cr3C2 particles, but it obviously influences the growth and orientation of crystal planes in composite coatings, especially at high nano-Cr3C2 particles content. Maximum microhardness was observed to be 595 Hv for Co-Ni-40g/L Cr3C2 coating and its wear resistance is the best at the same time.

Surface crystallographic structure insensitive growth of oriented graphene domains on Cu substrates

Cu-based chemical vapor deposition method can produce large-area graphene films, usually polycrystalline films with grain boundaries as the main defects. One way to reduce grain boundaries is to grow oriented graphene domains (OGDs), which can ultimately perfectly integrate. In contrast to previously reported methods of limiting OGD growth on Cu (1 1 1), we find that OGDs can grow on Cu substrates with a large surface crystallographic structure tolerance. Density functional theory calculations show that this is due to the single lowest energy state of graphene nucleation. The growth temperature is crucial. It must be high enough (1045 °C) to suppress mis-OGD nucleation, but not too high (1055 °C) to deteriorate OGD growth. Mis-OGD nucleation can also be caused by C impurity in Cu grains, which can be depleted by thermal pretreatment of the substrate in an oxidizing atmosphere. On the other hand, OGD growth is not sensitive to the atmosphere at growth stage within the range that we have tested.

In vitro corrosion resistance of a Ta2O5 nanofilm on MAO coated magnesium alloy AZ31 by atomic layer deposition

Micro-arc oxidation (MAO) coating with outstanding adhesion strength to Mg alloys has attracted more and more attention. However, owing to the porous structure, aggressive ions easily invaded the MAO/substrate interface through the through pores, limiting long-term corrosion resistance. Therefore, a dense and biocompatible tantalum oxide (Ta2O5) nanofilm was deposited on MAO coated Mg alloy AZ31 through atomic layer deposition (ALD) technique to seal the micropores and regulate the degradation rate. Surface micrography, chemical compositions and crystallographic structure were characterized using FE-SEM, EDS, XPS and XRD. The corrosion resistance of all samples was evaluated through electrochemical and hydrogen evolution tests. Results revealed that the Ta2O5 film mainly existed in the form of amorphousness. Moreover, uniform deposition of Ta2O5 film and effective sealing of micropores and microcracks in MAO coating were achieved. The current density (icorr) of the composite coating decreased three orders of magnitude than that of the substrate and MAO coating, improving corrosion resistance. Besides, the formation and corrosion resistance mechanisms of the composite coating were proposed.

ENHANCED STRUCTURAL AND OPTICAL PROPERTIES OF BISMUTH FERRITE (BiFeO3) NANOPARTICLES

Multiferroic Bismuth Iron Oxide (BiFeO3) nanoparticles was synthesized via sol gel method. This study demonstrated the preparation of nanoparticles of bismuth ferrite at 550ᵒC. In this method Bismuth nitrate [Bi (NO3)3.5H2O] and iron nitrate [Fe (NO3)3.9H2O] were used as starting chemical agent. In order to overcome the volatility of Bismuth at high temperature, different weight percentages of chemicals were used. Citric acid was used as chelating agent. Thermal treatment was given to the samples at 550ᵒC. Bismuth Ferrite nanoparticles showed obvious ferromagnetic properties. The size of Bismuth Ferrite nanoparticles reduced as magnetization increased. As the concentration of chemical increased at 550ᵒC the particle size was reduced due to recrystallization. Sol Gel method helped to control the size of crystals. The characterization of prepared samples of Bismuth Ferrite Nanoparticles was done by using X-ray diffraction (XRD), scanning electron microscope (SEM) and UV- visible for getting the information about surface morphology and crystallographic structure. X-ray diffraction result gave the information about the particle size and phase identification. UV- visible gave the information about the band gap energy of BiFeO3 nanoparticles. Scanning electron microscope result gave the information about surface morphology and grain size of nanoparticles at different resolutions.

Surface structure and stacking of the commensurate (13×13)R13.9∘ charge density wave phase of 1T−TaS2(0001)

By quantitative low-energy electron diffraction (LEED) we investigate the extensively studied commensurate charge density wave (CDW) phase of trigonal tantalum disulphide (1T-TaS$_2$), which develops at low temperatures with a $\left(\sqrt{13}\times\sqrt{13}\right)$R13.9{\deg} periodicity. A full-dynamical analysis of the energy dependence of diffraction spot intensities reveals the entire crystallographic surface structure, i.e. the detailed atomic positions within the outermost two trilayers consisting of 78 atoms as well as the CDW stacking. The analysis is based on an unusually large data set consisting of spectra for 128 inequivalent beams taken in the energy range 20-250 eV and an excellent fit quality expressed by a bestfit Pendry R-factor of R=0.110. The LEED intensity analysis reveals that the well-accepted model of star-of-David-shaped clusters of Ta atoms for the bulk structure also holds for the outermost two TaS$_2$ trilayers. Specifically, in both layers the clusters of Ta atoms contract laterally by up to 0.25 $\r{A}$ and also slightly rotate within the superstructure cell, causing respective distortions as well as heavy bucklings (up to 0.23 $\r{A}$) in the adjacent sulphur layers. Most importantly, our analysis finds that the CDWs of the 1$^{\text{st}}$ and 2$^{\text{nd}}$ trilayer are vertically aligned, while there is a lateral shift of two units of the basic hexagonal lattice (6.71 $\r{A}$) between the 2$^{\text{nd}}$ and 3$^{\text{rd}}$ trilayer. The results may contribute to a better understanding of the intricate electronic structure of the reference compound 1T-TaS$_2$ and guide the way to the analysis of complex structures in similar quantum materials.

Homologous substrate-temperature dependence of structure and properties of TiO2, ZrO2, and HfO2 thin films deposited by reactive sputtering

Group 4 metal oxides TiO2, ZrO2, and HfO2 were deposited on glass substrates at substrate temperatures ranging from 100 to 800 °C by reactive direct current magnetron sputtering using an Ar and O2 mixture as discharge gas. On the basis of the obtained cross-sectional and surface morphologies, crystallographic structures, and film properties, the homologous substrate-temperature dependence of the film structure and properties for the sputter-deposited metal oxide thin films are discussed. The x-ray diffraction measurements show the diffraction patterns characteristic of the anatase (tetragonal) structure at substrate temperatures below 400 °C and those of the rutile (tetragonal) structure at substrate temperatures above 600 °C for TiO2 thin films and the patterns attributable to the monoclinic structure with 〈−111〉 orientation for ZrO2 and HfO2 thin films. Scanning electron microscopy (SEM) observations show voided columnar structures with rough surfaces for TiO2 thin films and fine columnar structures with smooth surfaces for ZrO2 and HfO2 thin films, which is supported by the results obtained from atomic force microscopy (AFM) analysis. The quantitative data on the lattice strain, crystallite size, surface roughness, and refractive index are plotted against the homologous substrate temperature, Tsub/Tm (Tsub: substrate temperature and Tm: melting point of thin film materials). The lattice strain reaches approximately zero at Tsub/Tm = 0.3–0.35, suggesting that the residual stress is relaxed at this point, and the crystallite size reaches a plateau at the same range of Tsub/Tm. The surface roughness increases sharply after passing Tsub/Tm = 0.25–0.30, and the refractive index shows a rise at Tsub/Tm = 0.30–0.35. The images obtained by SEM and AFM are categorized based on the property transition observed in the quantitative property changes. The data obtained in this work are utilized to systematically study the effectiveness and appropriateness of the homologous (normalized) substrate temperature to explain the changes in structure, morphology, and properties of oxide thin films. Furthermore, it is suggested that the structure zone model, which is normally applied to sputtered metal films, is also applicable to sputtered oxide thin films.

Liquid Phase Exfoliation of Two-Dimensional Materials for Sensors and Photocatalysis-A Review.

Two-dimensional (2D) materials have rewritten many disciplines of modern science and technology, both through intensive fundamental research. In this review, we will provide a comprehensive summary of the properties, synthesis, characterization, and application of 2D materials (Graphene, Hexagonal boron nitride (h-BN) and transition dichalcogenide (TMD'S) in the context of electrochemistry and related scientific fields. 2D material nanosheets have been characterized by using different techniques such as X-ray diffraction, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), UV-Visible Spectroscopy, FT-IR Spectroscopy and Atomic Force Microscopy. 2D materials application revealed photo catalysis and sensors. Bottom-up approach and top-down methods have been proposed for exfoliation of layered materials. Graphene synthesis by chemical vapor deposition and transfer by roll-to-roll process or top-down method. Firstly, the structural, electronic, optical, and physical and chemical properties, and a variety of synthesis and characterization techniques of 2D materials are presented. Manganese dioxides (crystalline material) are significantly affected by the surface area, crystallographic structure and morphology, and synthetic route of production. Secondly, current electrochemical understanding of 2D and layered materials and their modification is discussed. Although broad in scope, this review is not an exhaustive list of facts; rather, it summarizes the established knowledge and pinpoints the most promising future trends.

Surface-enhanced Raman scattering studies of Cu/Cu2O Core-shell NPs obtained by laser ablation.

In order to perform SERS (surface-enhanced Raman scattering) measurements, spherical Cu/Cu2O core-shell NPs with a rather rough rugged surface and well-defined crystallographic structures were fabricated using nanosecond Ce: Nd YAG pulsed laser ablation in liquid (PLAL). Raman, Fourier transform infrared (FTIR) spectroscopy and TEM imaging of the prepared NPs reveal the existence of additional minority CuO phase, not determined earlier through XRD patterns. The SERS activity of Cu/Cu2O core-shell NPs substrates was investigated by using crystal violet (CV) and methylene blue (MB) as the analyte molecules under 532 nm excitation wavelength irradiation. The effect of localized surface plasmon resonance (LSPR) from Cu core contributing to the electromagnetic enhancement and Cu2O shell with a rough surface which itself contributes to chemical enhancement with adsorbed analyte molecule is due to a high overall SERS enhancement. The intensities of the totally and non-totally symmetric modes were used to calculate the degree of charge-transfer. The results demonstrate that the LSPR enhancement dominates charge-transfer resonance contribution in SERS of Cu/Cu2O-CV and Cu/Cu2O -MB systems. The reproducibility of the prepared SERS substrates was investigated and the SERS signals intensity variation was <28%.

Antimicrobial Effects of TiO2 Nanoparticles against Drug-Resistant Bacteria and Candida Albicans

Nanotechnology is expected to open new avenues to fight and prevent disease using atomic scale tailoring of materials. The metallic nanoparticles is the most promising nanomaterials with antibacterial properties and which exhibit increased chemical activity due to their large surface to volume ratios and crystallographic surface structure. This work focuses on the antibacterial activity of TiO2 against drug-resistant bacteria and Candida albicans. The antibacterial activity of TiO2 was evaluated using the determination of minimum inhibitory concentration (MIC) by the dilution method on agar medium. The obtained results show a significant antibacterial activity on the strains tested: Pseudomonas aeruginosa ATCC27853: 0.5 μg/mL, Staphylococcus aureus ATCC29213: 64 μg/mL, Escherichia coli ATCC25922: 128 μg/mL and Candida albicans 0.5 μg/mL. The Titanium Dioxide nanoparticles appear to be attractive candidates of choice to be an effective alternative to antibiotics and pave the way for a promising new strategy antibacterial nanoscale.