High-resolution Transmission Electron Microscopy Examination Research Articles

High-Resolution Characterization of Enamel Remineralization Using Time-of-Flight Secondary Ion Mass Spectrometry and Electron Microscopy

Introduction: The aim of this in vitro study was to assess the suitability of high-resolution time-of-flight secondary ion mass spectrometry (ToF-SIMS) for visualizing cross-sectional changes in human enamel microstructure and chemical composition during treatment and remineralization cycling of artificially generated caries lesions underneath an artificial plaque. Methods: Treatments consisted of exposure to twice daily toothpaste/water slurries prepared from 0, 1,100, and 5,000 μg/g fluoride (F) NaF/silica toothpastes. In addition, treatments with slurries prepared from 1,100 μg/g F SnF2/silica toothpastes were done using 44Ca in the remineralization solution to allow for differentiation of newly formed mineral and exploration of incorporated metal dopants using ToF-SIMS. Complementary microhardness, scanning electron microscopy, and high-resolution transmission electron microscopy (HR-TEM) investigations were performed on enamel cross sections. Results: HR-TEM was used for the first time to determine the change in crystallinity during remineralization revealing distinct microstructural zones within one lesion. Chemical mapping using ToF-SIMS demonstrated that the distribution of F, while observed primarily in the new mineral phase, was widespread throughout the lesion with 44Ca substantially limited to the remineralizing mineral. Both penetrated the inter-rod spaces of the sound enamel illustrating how acid damage propagates into the native mineral as the caries lesion deepens. HR-TEM examination revealed different regions within the lesion characterized by distinct micro- and ultrastructures. Importantly, HR-TEM revealed a return of crystallinity following remineralization. F dose-response observations verified the ability of these high-resolution techniques to differentiate remineralization efficacy. Conclusion: The collective results provided new insights such as the visualization of F or calcium penetration pathways, as well as new tools to study the caries process.

Oblique nanomachining of gallium arsenide explained using AFM experiments and MD simulations

Gallium Arsenide (GaAs) continues to remain a material of significant importance due to being a preferred semiconductor substrate for the growth of quantum dots (QDs) and GaAs-based quantum devices used widely in fifth-generation (5G) wireless communication networks. In this paper, we explored aspects of oblique nanomachining to investigate the improvement in the machining quality as well as to understand plasticity and transport phenomena in GaAs using atomic scale machining experiments and simulations. We studied the influence of the direction vector of the cutting tip (e.g. tip alignment) during the surface generation process in GaAs. We noticed a novel observation that when the AFM tip's cutting edge presented two acute angles (i.e., 30° angles each) between the cutting face and the cutting direction (which can be regarded as an oblique cutting condition), the cutting configuration involved early avalanche of dislocations compared to other tip configurations (e.g., orthogonal cutting). Orthogonal cutting involved the least coefficient of friction but the highest specific cutting energy compared to oblique cutting. High-resolution transmission electron microscopy (HRTEM) examination revealed that the shuffle-set slip on the {1 1 1} slip system due to the 〈1 1 0〉 type dislocation paves the way for plasticity during nanometric cutting of GaAs. Overall, a particular condition of oblique cutting was inferred to be the best for nanofabrication of high-quality wafers using an AFM.

In Vitro Antibacterial and Wound Healing Activities Evoked by Silver Nanoparticles Synthesized through Probiotic Bacteria.

The prospective application of probiotics is an adjuvant for the advancement of novel antimicrobial and wound-healing agents. Currently, probiotic bacteria are utilized for the biosynthesis of nanoparticles in the development of innovative therapeutics. The present study aimed at using nanoparticle-conjugated probiotic bacteria for enhanced antibacterial and wound-healing activity. In the present investigation, the probiotic bacteria were isolated from a dairy source (milk from domestic herbivores). They screened for antibacterial activity against infection-causing Gram-negative (Pseudomonas aeruginosa and Escherichia coli) and Gram-positive (Bacillus subtilis and Staphylococcus aureus) pathogens. Further, the probiotic strain with higher bactericidal activity was used to synthesize silver, selenium, and copper nanoparticles. The isolated strain was found to be Lactiplantibacillus plantarum and it only has the ability to synthesize silver nanoparticles. This was verified using Ultra violet-Visible (UV-Vis) spectroscopy, where the test solution turned brown and the greatest UV-Vis absorptions peaked at 425 nm. Optimization studies on the synthesis of AgNPs (silver nanoparticles) are presented and the results show that stable synthesis was obtained by using a concentration of 1mM silver nitrate (AgNO3) at a temperature of 37 °C with pH 8. The FTIR (Fourier transform infrared spectroscopy) study confirmed the involvement of functional groups from the cell biomass that were involved in the reduction process. Additionally, biosynthesized AgNPs showed increased antioxidant and antibacterial activities. The nano silver had a size distribution of 14 nm and was recorded with HR-TEM (high-resolution transmission electron microscopy) examination. The EDX (energy dispersive X-ray) analysis revealed 57% of silver groups found in the nanoparticle production. The biosynthesized AgNPs show significant wound-healing capabilities with 96% of wound closure (fibroblast cells) being observed through an in vitro scratch-wound assay. The cytotoxic experiments demonstrated that the biosynthesized AgNPs are not extremely hazardous to the fibroblast cells. The present study provides a new platform for the green synthesis of AgNPs using probiotic bacteria, showing significant antibacterial and wound-healing potentials against infectious pathogens.

Generation of Hydrogen Gas Using CuCr2O4-g-C3N4 Nanocomposites under Illumination by Visible Light.

In this research, nanocomposites made of CuCr2O4-g-C3N4 accommodating distinct contents of CuCr2O4 (1–4 wt %) nanoparticles (NPs) were endorsed for hydrogen gas production after illumination by visible light in the presence of aqueous glycerol solution. The ultrasonication-mixture method was applied to assure the homogeneous distribution of CuCr2O4 NPs over synthesized mesoporous g-C3N4. Such nanocomposites possess suppressed recombination between the photoinduced charges. High-resolution transmission electron microscopy and X-ray photoelectron spectroscopy examinations affirmed the formation of CuCr2O4-g-C3N4 heterojunctions. The separation between the induced charges and the photocatalytic performance with the CuCr2O4 NP amount were investigated. The CuCr2O4-g-C3N4 heterojunction of 3 wt % CuCr2O4 content was documented as the optimal heterojunction. Upgraded hydrogen gas generation was attained over the optimal heterojunction with the extent of ten and thirty times as those registered for pure CuCr2O4 and g-C3N4 specimens, respectively, under illumination by visible light. The photocatalytic performance acquired by the diverse synthesized specimens was assessed not only by their effectiveness to absorb light in the visible region but also by their potential to separate the photoinduced charges.

Magnetism modulation and conductance quantization in a gadolinium oxide memristor.

The requests for higher information storage density, greater data processing power, and memory-centric computing capability in the current big data era are motivating global research interests in novel solid-state electronic devices that can unite the electron charge and spin degrees of freedom. Herein, the simultaneous realization of magnetism modulation and conductance quantization in a single gadolinium oxide memristor is reported. A remarkable enhancement of >170% in saturation magnetization at room temperature, accompanied by the emergence of a clear magnetoresistance behavior at low temperature, was obtained after setting the memristor from the initial high resistance state (HRS) into the low resistance state (LRS). By carefully resetting the memristor from the LRS into the HRS, up to 32 quantized conductance states with good repeatability and stability were observed, which could possibly allow achieving 5 bit storage in a single memory cell in the future. Moreover, the resistive switching mechanism of the memristor was thoroughly investigated with the help of temperature-dependent resistance tests and high-resolution transmission electron microscopy examination. This work could provide a powerful approach to design future multi-field modulated, high-performance information devices with integrated data storage, sensing, as well as processing functions.

Semi-transparent perovskite solar cells with directly sputtered amorphous InZnSnO top cathodes for building integrated photovoltaics

Abstract We report on a low plasma damage sputtering amorphous InZnSnO (IZTO) top cathode prepared using linear facing target sputtering (LFTS) at room temperature for semi-transparent perovskite solar cells (PSCs) to be applied as building integrated photovoltaics. The effective confinement of high-density plasma between InZnO and InSnO targets by directional magnet fields and negative bias applied simultaneously on both targets led to the successful sputtering of the amorphous IZTO top cathode on the semi-transparent PSCs without plasma damage or degradation of PSC performance. At an optimal sputtering condition of the IZTO top cathode, the semi-transparent PSC showed an open circuit voltage (1.056 V), short circuit current (16.79 mA/cm2), fill factor (51.19%), and power conversion efficiency (9.081%) comparable to those of reference PSC with an Ag metal top cathode. Based on synchrotron GIWAXS and high-resolution transmission electron microscopy examinations, we suggested a possible mechanism with which to explain the plasma damage effect on the performance of PCSs while sputtering IZTO top cathode on semi-transparent PSCs.

Synthesis and characterization of crustin capped titanium dioxide nanoparticles: Photocatalytic, antibacterial, antifungal and insecticidal activities

Current scenario of bio-nanotechnology, successfully fabrication of ultrafine titanium dioxide nanoparticles (TiO2NPs) using various biological protein sources for the multipurpose targets. The present research report involves synthesis of TiO2NPs using antimicrobial peptide (AMP) crustin (Cr). Crustin previously purified from the blue crab, Portunus pelagicus haemolymph, by blue Sepharose CL-6B matrix assisted affinity column chromatography. Synthesized Cr-TiO2NPs was physico-chemically characterized by UV–Visible spectroscopy (UV–Visible), X-ray Diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High-resolution transmission electron microscopy (HR-TEM) and zeta potential examination. X-ray diffraction analysis for crystalline nature and phase identification of titanium dioxide nanoparticles was absorbed. Functional groups were found through FTIR ranges between 1620 and 1700 cm−1. HR-TEM analysis showed that the synthesized Cr-TiO2NPs tetragonal shape and sizes ranging from 10 to 50 nm. Finally, the surface charge of the Cr-TiO2NPs was confirmed through zeta potential analysis. Furthermore, the characterized Cr-TiO2NPs exhibited good biofilm inhibition against GPB - S. mutans (Gram Positive Bacteria- Streptococcus mutans), GNB - P. vulgaris (Gram Negative Bacteria- Proteus vulgaris) and fungal Candida albicans. Moreover, photocatalysis demonstrated that the Cr-TiO2NPs was effectively explored the degradation of dyes. The results suggest that Cr-TiO2NPs is an excellent bactericidal, fungicidal and photocatalytic agent that can be supportively used for biomedical and industrial applications.

Crack propagation mechanisms of an aged nickel-titanium-hafnium shape memory alloy

Mechanisms of crack propagation in a NiTiHf sample were studied from post-mortem microstructure characterizations about cracks. Transmission electron microscopy (TEM) analysis showed that a crack propagated within a martensite band along 〈011〉 type II twin planes. The crack was observed to switch between different twin planes to avoid precipitates. The crack tip terminated outside of the martensite band, within surrounding austenite. Amorphization of crack edges in both austenite and martensite was also detected, together with Ni enrichment. High-resolution TEM examination of crack tip inside the austenite phase also confirmed the formation of martensite nanocrystals embedded in the amorphous regions.

Thermodynamic and microstructural study of Ti2AlNb oxides at 800\u2009\xb0C

The high-temperature structural applications of Ti2AlNb-based alloys, such as in jet engines and gas turbines, inevitably require oxidation resistance. The objective of this study is to seek fundamental insight into the oxidation behavior of a Ti2AlNb-based alloy via detailed microstructural characterization of oxide scale and scale/substrate interface after oxidation at 800 °C using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and transmission electron microscopy (TEM). The oxide scale exhibits a complex multi-layered structure consisting of (Al,Nb)-rich mixed oxide layer (I)/mixed oxide layer (II)/oxygen-rich layer (III)/substrate from the outside to inside, where the substrate is mainly composed of B2 and O-Ti2AlNb phases. High-resolution TEM examinations along with high-angle annular dark-field (HAADF) imaging reveal: (1) the co-existence of two types (α and δ) of Al2O3 oxides in the outer scale, (2) the presence of metastable oxide products of TiO and Nb2O5, (3) an amorphous region near the scale/substrate interface including the formation of AlNb2, and (4) O-Ti2AlNb phase oxidized to form Nb2O5, TiO2 and Al2O3.

Structural-Ordered Flexible Polypyrrole Films Derived from Vapor Phase Polymerization Process As Ultrahigh-Rate Anodes for Li-Ion and Na-Ion Batteries

Recently, there has been strong market demand for thin, lightweight, flexible and bendable electrodes to make lithium ion batteries (LIBs) or lithium-polymer batteries that are lighter and more flexible than the existing ones, and thus more capable of satisfying for portable soft or bendable electronic devices such as roll-up displays, integrated circuit smart cards and wearable devices for durability in everyday use[1]. In this respect, the concept of all-polymer based batteries and supercapacitors, introduced almost three decades ago[2], has recently gained renewed interest mainly due to long cycle life, low self-discharge rate, endurance to over-discharge, low manufacturing costs, and shape flexibility of conductive polymers. Several important conducting polymers such as polypyrrole (PPy) [3], polyaniline (PAN) [4], and polythiophene (PTh) [5] and their derivatives have been proved to be used not only as the cathode but also as the anode for the secondary battery because they are stable in air and have good electrochemical properties.On the other hand, considering the limited and uneven distribution of lithium minerals, room temperature sodium ion batteries (SIBs) have received growing attention because of their low cost and abundant supply. SIBs and LIBs share the same architecture of battery design. One of the major challenges for SIBs is to discover suitable electrode materials with high and stable sodium storage capabilities. The lithium or sodium storage mechanism of the conductive polymers is reversible n-doped behavior[6]. During discharge process, the cations (Li+ or Na+) stored between the chain layers of polymers and combined with oxygen atom to form oxide[3]. Therefore, the distance between the chain layers is important for the cations insertion and extraction, especially for the sodium ions with larger atomic radius. Among the conducting polymers, PPy have drawn the most attention due to their redox properties, biocompatibility, good electrical conductivity, and chemical stability. However, to the best of our knowledge, very few PPy materials have been reported for Na-ion storage. In this work, we propose PPy thin films with stable chain-layer structure as anodic electrodes for LIBs and SIBs, which synthesized by an easy, inexpensive and scalable vapor phase polymerization (VPP) technique[7]. The ordered pyrrolic chains layer structure of obtained PPy film was characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), Raman spectra and X-ray photoelectron spectra (XPS) examinations. As a consequence, the PPy film demonstrates excellent rate performance and cycling stability as freestanding anodic electrode for both Li-ion and Na-ion storage. In particular, the PPy film anode exhibits an impressive increased reversible capacity of 204.5 mAh g-1 even after 400 cycles at 10 C charge/discharge rate for Li-ion storage. Moreover, a reversible redox capacity of 113.8 mAh g-1 through doping-dedoping reactions of Na-ions into/from the PPy chains is also achieved. The electrochemical Li-ions and Na-ions doping-dedoping behaviors of PPy film was investigated by ex-situ XRD. It was proved that PPy film electrode could be reversibly charged and discharged with lithium and sodium and the ordered pyrrolic chains structure can self-adapt the doped ions. The results may substantially contribute to the progress of the flexible polymer electrode for various ions batteries. Acknowledgements: The authors gratefully acknowledge the support of the National Science Foundation of China (51472161, 51472160, 21403139), the Shanghai Pujiang Program (No. 14PJ1407100), the Key Program for the Fundamental Research of the Science and Technology Commission of Shanghai Municipality (15JC1490800, 12JC1406900) and the International Cooperation Program of the Science and Technology Commission of Shanghai Municipality (14520721700). We acknowledge the support of the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (TP2014048) and the Hujiang Foundation of China (B14006).

Synthesis of carbon-encapsulated cobalt sulfide nanoparticles and their electrochemical property

Carbon coated cobalt sulfide (Co9S8) nanoparticles (C@Co9S8) with the size of 5 to 30 nm were synthesized in a controllable way. The products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), and galvanostatic charge-discharge. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) examinations confirmed that the C@Co9S8 nanoparticles were uniformly dispersed in carbon matrix, and the Co9S8 nanoparticles were surrounded by several carbon layers with well-ordered arrangement. The nanoparticles exhibited well-constructed core-shell structures. The possible growth process for the C@Co9S8 was discussed briefly. The electrochemical measurements were examined in a three-electrode glass cell in 1.0 M H2SO4 solutions. The C@Co9S8 nanocomposites are demonstrated to be an excellent electrode material with good specific capacitance.

Statistical analysis of support thickness and particle size effects in HRTEM imaging of metal nanoparticles

High-resolution transmission electron microscopy (HRTEM) examination of nanoparticles requires their placement on some manner of support – either TEM grid membranes or part of the material itself, as in many heterogeneous catalyst systems – but a systematic quantification of the practical imaging limits of this approach has been lacking. Here we address this issue through a statistical evaluation of how nanoparticle size and substrate thickness affects the ability to resolve structural features of interest in HRTEM images of metallic nanoparticles on common support membranes. The visibility of lattice fringes from crystalline Au nanoparticles on amorphous carbon and silicon supports of varying thickness was investigated with both conventional and aberration-corrected TEM. Over the 1–4nm nanoparticle size range examined, the probability of successfully resolving lattice fringes differed significantly as a function both of nanoparticle size and support thickness. Statistical analysis was used to formulate guidelines for the selection of supports and to quantify the impact a given support would have on HRTEM imaging of crystalline structure. For nanoparticles ≥1nm, aberration-correction was found to provide limited benefit for the purpose of visualizing lattice fringes; electron dose is more predictive of lattice fringe visibility than aberration correction. These results confirm that the ability to visualize lattice fringes is ultimately dependent on the signal-to-noise ratio of the HRTEM images, rather than the point-to-point resolving power of the microscope. This study provides a benchmark for HRTEM imaging of crystalline supported metal nanoparticles and is extensible to a wide variety of supports and nanostructures.

Fabrication and characterization of nanoparticle MgO/B4C composite by mechanochemical method

In this study, nanoparticle boron carbide was produced after the reduction of boron oxide with magnesium under the presence of carbon by using mechanochemical synthesis method. During the synthesis processing, microstructure and phase transformations of powders were performed by using X-ray diffraction (XRD), Fourier-transform infrared spectrum (FT-IR), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM). At the end of 2 h, reaction products (MgO, B4C) were determined by XRD and FT-IR examinations. Nanoparticle B4C single-phase crystalline structure from the MgO/B4C composite powder mixture, which was the reaction product, was obtained by leaching process. With the increase in the synthesis period, starting material peaks diminished and Fe peak intensity became evident. After the HRTEM examinations, it was determined that synthesized B4C particles were within range of 10–200 nm especially in the activation of leaching process. Additionally, by using spot pattern analysis method, planes represented by B4C particles were calculated.

Ultrafine particulate matter formation in the early stage of pulverized coal combustion of high-sodium lignite

Abstract In this work, the pulverized coal combustion of Zhundong lignite was conducted in an optically-accessible, downward Hencken flat-flame burner to investigate the incipient formation of ultrafine particulate matter (PM). The ultrafine PM were collected in - flame from distinct positions under 1800 K, 1500 K and 1200 K using a self-designed thermophoretic sampler, together with extensive conventional transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDS) examinations. A novel in situ low-intensity phase-selective laser-induced breakdown spectroscopy (PS-LIBS) was further introduced to diagnose the dynamic behavior of particle-phase sodium during the pulverized coal combustion. The primary particles in the collected ultrafine PM have mean diameter of 8–15 nm, with Si and Na as main mineral components based on TEM/HRTEM–EDS results. The formation of ultrafine PM is regarded as a process of multi-component flame syntheses of mineral precursors, in which the competition between the devolatilization and the coalescence of particles are of most significance. Finally, based on an approach of time scale analysis, three characteristic times of minimum mean diameter of primary particles, the initial increment point of particle-phase sodium and the maximum devolatilization are found to be highly correlated.

Synthesis of carbon nanofibres from waste chicken fat for field electron emission applications

Carbon nanofibres (CNFs) with sea urchin-like morphology were synthesised from waste chicken fat precursor via catalytic thermal chemical vapour deposition method at 750°C. The CNFs showed amorphous structures under high-resolution transmission electron microscopy, micro-Raman spectroscopy and X-ray diffraction examination. X-ray photoelectron spectroscopy analysis confirmed that the core of the sea urchin-like CNFs was composed of Fe3C formed within the first 20min of synthesis time. The growth of amorphous CNFs from agglomerated Fe3C particles was favourable due to the high heating rate applied during the synthesis. Field electron emission examination of the CNFs indicated turn-on and threshold field values of 5.4 and 6.6Vμm−1 at current density of 1 and 10μAcm−2, respectively. This study demonstrates that waste chicken fat, a low-cost and readily available resource, can be used as an inexpensive carbon source for the production of CNFs with a potential application in field electron emitters.

Ceramic Nano-particle/Substrate Interface Bonding Formation Derived from Dynamic Mechanical Force at Room Temperature: HRTEM Examination

The bonding of TiO2 nano-particle/substrate is a critical factor influencing the performance of dye-sensitized solar cells. In order to reveal the bonding properties at TiO2 nano-particle/substrate interface, high-resolution transmission electron microscopy (HRTEM) analysis was adopted to TiO2 coatings prepared by three different approaches. In the HRTEM analysis, the effective bonding mode is allowed to distinguish from the false image overlapping. Results show that large areas of effective bonding between nano-TiO2 particles and the substrate surface formed in the room temperature cold sprayed coating and mechanically pressed coating, while only limited interface areas with the effective bonding were observed in the coating deposited by non-pressed method. These results confirm that both high impact pressure during the room temperature cold spraying and mechanical pressure contribute to the bonding formation at the particle/substrate interface.

Synthesis of Zirconia Oxide (ZrO<sub>2</sub>) Nanofibers on Zirconnia Substrates by Ultrasonic Spray Pyrolysis

Zirconia oxide (ZrO2) nanofibers were synthesized using Phosphorus/water mixture as catalyst by ultrasonic spray pyrolysis CVD on the zirconia substrate at 900°C for 1 h in N2 gas. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) examinations show that all the synthesized nanofibers have uniform surface morphology and their diameters are in the range of 100 nm. The HRTEM selected-area electron diffraction pattern (SAED) shows that crystalline ZrO2 phase exist in the nanofibers, and the energy-dispersive x-ray spectroscopy (EDS) results show that the elements of Zr and O are uniformly distributed across the nanofiber matrix. The phosphorus atoms corroded the entire Zirconia substrate surface, and the Zirconia-Phosphorus liquid-catalyzed the solid-liquid-solid mechanism is proposed to explain the growth of the nanofibers.

Epitaxial Grain Growth During Splat Cooling of Alumina Droplets Produced by Atmospheric Plasma Spraying

Alumina splats were deposited on polished single crystal alumina substrates with two different crystalline facet orientations of [001] and [110] by atmospheric plasma spraying at a substrate preheating temperature of 900 °C to examine the epitaxy during splat cooling. The cross-sectional samples for high-resolution transmission electron microscopy examination were prepared by focused ion beam-assisted-scanning electron microscopy (FIB-SEM). The results show that the whole splats with a thickness ranging from ~600 to ~1000 nm exhibit the same crystalline structure as the substrate. Moreover, the splat deposited on the single crystalline alumina substrates exhibits exactly the same orientation as the substrate. The results evidently indicate that the epitaxial grain growth occurs after alumina droplets impact on the single crystal alumina substrate. The present results suggest that the crystalline structure of alumina deposit formed by plasma spraying can be possibly controlled by the coating surface temperature.

Electronic structure of chromium-containing amorphous hydrogenated carbon thin films studied by X-ray absorption spectroscopy

C K-, Cr L3.2-, and K-edge X-ray absorption near-edge structure (XANES) analysis, high-resolution transmission electron microscopy examination, and optical absorptance have been examined to obtain a correlation between the optical absorptance and electronic structure of chromium-containing amorphous hydrogenated carbon thin films (a-C:H/Cr) deposited using a dc magnetron sputter deposition technique. It was found that the C 2pCr 3d hybridization gradually increases as the Cr nanoparticle (NP) size decreases, accompanied by a C 2p interband transition. The amount of CH bonding and the change in crystalline structure are the main factors affecting the optical absorptance of the thin films. The size of the Cr NP affects the absorption wavelength range of the films. The optical absorptance and C K-edge XANES spectra indicate that a decrease in the size of Cr NP raises the conduction-band-minimum and may also increase the bandgap.

Design and controllable synthesis of α-/γ-Bi2O3 homojunction with synergetic effect on photocatalytic activity

A α-/γ-Bi2O3 composite has been successfully prepared via a hydrothermal method. The as-prepared nanocrystals are characterized by the X-ray diffraction, Fourier transformation infrared spectrum, Scanning electron microscopy, Transmission electron microscopy, and high-resolution transmission electron microscopy examination. The homojunction between the α-Bi2O3 and γ-Bi2O3 is confirmed by the diffuse reflectance spectra and impedance spectrum. The photocatalytic activities of the samples were evaluated by the degradation of Rhodamine B as a model pollutant. The composite exhibited higher photocatalytic activity than bare α-Bi2O3 or γ-Bi2O3 in the degradation of RhB. The enhanced photocatalytic activity is attributed to the synergetic effect of the homojunction.