Core-shell particles of C-doped CdS and graphene: A noble metal-free approach for efficient photocatalytic H_(2) generation

To achieve efficient photocatalytic H_(2) generation from water using earth-abundant and cost-effective materials,a simple synthesis method for carbon-doped CdS particles wrapped with graphene(C-doped CdS@G)is reported.The doping effect and the application of graphene as cocatalyst for CdS is studied for photocatalytic H_(2) generation.The most active sample consists of CdS and graphene(CdS-0.15G)exhibits promising photocatalytic activity,producing 3.12 mmol g^-(1) h^-(1) of H_(2) under simulated solar light which is^4.6 times superior than pure CdS nanoparticles giving an apparent quantum efficiency(AQY)of 11.7%.The enhanced photocatalytic activity for H_(2) generation is associated to the narrowing of the bandgap,enhanced light absorption,fast interfacial charge transfer,and higher carrier density(N_(D))in C-doped CdS@G samples.This is achieved by C doping in CdS nanoparticles and the formation of a graphene shell over the C-doped CdS nanoparticles.After stability test,the spent catalysts sample was also characterized to investigate the nanostructure.

Preparation and Enhanced Daylight-Induced Photo-Catalytic Activity of Transparent C-Doped TiO_2 Thin Films

The transparent C-doped TiO2 nanostructure films were fabricated on the silicate glass substrates by sol-gel spin-coated method. The as-prepared films were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, UV-visible absorption spectra （UV-vis） and X-ray photoelectron spectroscopy （XPS）. The photocatalytic activity was evaluated via the photocatalytic oxidation of methylene blue in aqueous under daylight irradiation at room temperature. The results show that the daylight-induced photocatalytic activities of the as-prepared films are improved by the C-doping. The calcination temperatures significantly affect the morphology, microstructure and photocatalytic activity of the as-prepared samples. At 723 K, the C-doped TiO2 films exhibit the highest photocatalytic activity due to the synergetic effects of good crystallization, appropriate oxygen vacancies and strong absorption in the near UV and visible-light region.

Structural Evolution and Phase Change Properties of C-Doped Ge_2Sb_2Te_5 Films During Heating in Air

We elucidate the importance of a capping layer on the structural evolution and phase change properties of carbondoped Ge2 Sb2 Te5（C-GST） films during heating in air. Both the C-GST films without and with a thin SiO2 capping layer（C-GST and C-GST/SiO2） are deposited for comparison. Large differences are observed between C-GST and C-GST/SiO2 films in resistance-temperature, x-ray diffraction, x-ray photoelectron spectroscopy,Raman spectra, data retention capability and optical band gap measurements. In the C-GST film, resistancetemperature measurement reveals an unusual smooth decrease in resistance above 110℃ during heating. Xray diffraction result has excluded the possibility of phase change in the C-GST film below 170℃. The x-ray photoelectron spectroscopy experimental result reveals the evolution of Te chemical valence because of the carbon oxidation during heating. Raman spectra further demonstrate that phase changes from an amorphous state to the hexagonal state occur directly during heating in the C-GST film. The quite smooth decrease in resistance is believed to be related with the formation of Te-rich GeTe4-n Gen（n = 0, 1） units above 110℃ in the C-GST film. The oxidation of carbon is harmful to the C-GST phase change properties.

The First Principle Study on C-doped Armchair Boron Nitride Nanoribbon Rectifier

The electronic transport properties of armchair-edged boron nitride nanoribbons（ABNNRs） devices were investigated by the first principle calculations. The calculated results show that the ABNNR device doped with carbon atoms in one of the electrodes acts as a high performance nanoribbon rectifier. It is interesting to find that there exists a particular bias-polarity-dependent matching band between two electrodes,leading to a similar current-voltage（I-V） behavior as conventional P-N diodes. The I-V behavior presents a linear positive-bias I-V characteristic,an absolutely negligible leakage current,and a stable rectifying property under a large bias region. The results suggest that C doping might be an effective way to raise ABNNRs devices＇ rectifying performance.

Ceftriaxone sodium degradation by carbon quantum dots(CQDs)-decorated C-doped a-Bi_(2)O_(3) nanorods

A novel carbon quantum dots decorated C-doped a-Bi_(2)O_(3)photocatalyst(CBO/CQDs)was synthesized by solvothermal method.The synergistic effect of adsorption and photocatalysis highly improved contaminants removal efficiencies.The ceftriaxone sodium degradation rate constant(k)of CBO/CQDs was 11.4 and 3.2 times that of pure a-Bi2O3 and C-doped a-Bi_(2)O_(3),respectively.The interstitial carbon doping generated localized states above the valence band,which enhanced the utilization of visible light and facilitated the separation of photogenerated electrons and holes;the loading of CQDs improved the charge carrier separation and extended the visible light response;the reduced particle size of CBO/CQDs accelerated the migration of photogenerated carriers.The·O2-and ht were identified as the dominant reactive species in ceftriaxone sodium degradation,and the key role of·O2-was further investigated by NBT transformation experiments.The Fukui index was applied to ascertain the molecular bonds of ceftriaxone sodium susceptible to radical attack,and intermediates analysis was conducted to explore the possible degradation pathways.The toxicity evaluation revealed that some degradation intermediates possessed high toxicity,thus the contaminants require sufficient mineralization to ensure safe discharge.The present study makes new insights into synchronous carbon dopping and CQDs decoration on modification of a-Bi2O3,which provides references for future studies.

Supercritical fluid-assisted fabrication of C-doped Co_(3)O_(4) nanoparticles based on polymer-coated metal salt nanoreactors for efficient enzyme-mimicking and glucose sensor properties

Nanomaterials doped with non-metallic C have attracted tremendous attention as potential nano-artificial enzymes due to their ability to change the energy band structure to improve their intrinsic properties.Herein,we report a green,facile,efficient,fast strategy to access high-performance nanozymes via supercritical CO_(2)fluid technology-fabricated polymer nanoreactor of poly-(methyl vinyl ether-co-maleic anhydride)(PVM/MA)coated Co(NO_(3))_(2)into C-doped Co_(3)O_(4)(C-Co_(3)O_(4))nanozyme by a onestep calcination process.Converting PVM/MA to C doping into Co_(3)O_(4)shortens the entire lattice constant of the crystal structure,and the overall valence band energy level below the Fermi level shifts toward the lower energy direction.The as-prepared CCo_(3)O_(4)demonstrated significant peroxidase-like catalytic activity,significantly greater than the undoped Co_(3)O_(4)nanoparticle nanozyme.The following density functional theory(DFT)calculations revealed that the doped nano-enzyme catalytic site displayed a unique electronic structure,altering the material surface with more electrons to fill the anti-bond of the two molecular orbitals,significantly improving the peroxidase-like enzyme catalytic and glucose sensor performance.The resultant enzymatic glucose sensing in a linear range of 0.1–0.6 mM with a detection limit of 3.86μM is in line with standard Michaelis–Menten theory.Collectively,this work demonstrates that converting polymers into nanozymes of C-doped form by supercritical CO_(2)fluid technology in a step is an effective strategy for constructing high-performance glucose sensor nanozymes.This cost-effective,reliable,precise system offers the potential for rapid analyte detection,facilitating its application in a variety of fields.

Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B

Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria （Microcystis sp.） were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible- light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B （RhB） degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions.

Synthesis and Visible-light Photocatalytic Performance of C-doped Nb2O5 with High Surface Area

C-doped Nb2O5 with abundant mesopores has been successfully synthesized through a facile solvothermal synthetic strategy followed by calcination treatment. The resulting C-doped Nb2O5 displayed the highest BET surface area（345 m^2/g） and large mesopore size（ca. 4.2 nm）, capable of offering more accessible active sites as well as faster mass transfer for catalysis. Besides, the doping of C（2.21%, molar fraction） at the O sites in Nb2O5 lattice greatly enhanced visible-light response by lowering the band gap, thereby making the material a photocatalyst under visible-light irradiation. Typically, the C-doped Nb2O5 exhibited a high H2 evolution rate of ca. 39.10·μmol·g^-1·h^-1 and also degraded RhB dye completely after 30 min of visible light exposure, which turned out to be much better than Degussa P25 and pure Nb2O5 catalysts.

Investigation of microstructure modification of C-doped a-SiO_2/Si after Pb-ion irradiation

Thermally grown amorphous SiO2 （a-SiOz） films were implanted at room temperature （RT） with 100 keV C-ions to 5.0× 10^17 ions/cm2. These samples were irradiated at RT with 853 MeV Pb-ions to 1.0x 1012 and 5.0× 10^12 ions/cm2. Then the samples were investigated using Transmission Electron Microscopy （TEM） at RT. Significant microstructure modifications were observed in C-doped a-SiO2/Si samples after high energy Pb-ion irradiations, and the formation of new structures depended strongly on the Pb-ion irradiation fluences. For example, tracks in high density were observed in a 1.0× 10^12 Pb/cm2 irradiated and C-doped sample. Additionally, the length of tracks grows, and a large number of 8H-SiC nanocrystals can be seen in the film when irradiation fluence is increased to 5.0× 10^12 Pb/cm2. Possible modification processes of C-doped a-SiO2 under swift heavy ion irradiations are briefly discussed.

Raman scattering investigation of C-doped a-SiO_2 after high energy heavy ion irradiations

Thermally grown amorphous SiO2 films were implanted at room temperature with 100 keV C-ions to 5.0× 10^17 or 1.2× 10^18 ions/cm2. These samples were irradiated at room temperature with 853 MeV Pb-ions to 5.0× 10^11, 1.0× 10^12, 5.0× 10^12 ions/cm2, or with 308 MeV Xe-ions to 1.0× 10^12, 1.0× 10^13, 1.0× 10^14 ions/cm2, respectively. Then the samples were investigated using micro-Raman spectroscopy. Prom the obtained Raman spectra, we deduced that Si-C bonds and sp2 carbon sites were created and nano-inclusions may also be produced in the heavy ion irradiated C-doped SiO2. Furthermore, some results show that Pb ion irradiations could produce larger size inclusions than Xe ions and the fluence. The possible modification process of C-doped discussed. inclusion size decreased with increasing the irradiation a-SiO2 under swift heavy ion irradiations was briefly

Self-catalytic induced interstitial C-doping of Pd nanoalloys for highly selective electrocatalytic dehydrogenation of formic acid

Light-metalloid-atom-doped Pd interstitial nanoalloy is promising candidate for electrocatalysis because of the favorable electronic effect.Herein,an innovative method was developed to synthesize C-doped Pd interstitial nanoalloy using palladium acetate both as metal precursor and C dopant.Elaborate characterizations demonstrated that C atoms were successfully doped into the Pd lattice via self-catalytic decomposition of acetate ions.The as-synthesized C-doped Pd catalysts showed excellent activity and durable stability for formic acid electrooxidation.The mass activity and specific activity at 0.6 V of C-doped Pd were approximately 2.59 A/mg and 3.50 mA cm^(-2),i.e.,2.4 and 2.6 times of Pd,respectively.DFT calculations revealed that interstitial doping with C atoms induced differentiation of Pd sites.The strong noncovalent interaction between the Pd sites and the key intermediates endowed Pd with high-selectivity to direct routes and enhanced CO tolerance.This work presents a sites-differentiation strategy for metallic catalysts to improve the electrocatalysis.

Novel GaN-based double-channel p-heterostructure field-effect transistors with a p-GaN insertion layer

GaN-based p-channel heterostructure field-effect transistors(p-HFETs)face significant constraints on on-state currents compared with n-channel high electron mobility transistors.In this work,we propose a novel double heterostructure which introduces an additional p-GaN insertion layer into traditional p-HFETs.The impact of the device structure on the hole densities and valence band energies of both the upper and lower channels is analyzed by using Silvaco TACD simulations,including the thickness of the upper AlGaN layer and the doping impurities and concentration in the GaN buffer layer,as well as the thickness and Mg-doping concentration in the p-GaN insertion layer.With the help of the p-GaN insertion layer,the C-doping concentration in the GaN buffer layer can be reduced,while the density of the two-dimensional hole gas in the lower channel is enhanced at the same time.This work suggests that a double heterostructure with a p-GaN insertion layer is a better approach to improve p-HFETs compared with those devices with C-doped buffer layer alone.

Oxygen Functionalization-Induced Charging Effect on Boron Active Sites for High-Yield Electrocatalytic NH_(3) Production

Ammonia has been recognized as the future renewable energy fuel because of its wide-ranging applications in H_(2) storage and transportation sector.In order to avoid the environmentally hazardous Haber-Bosch process,recently,the third-generation ambient ammonia synthesis has drawn phenom-enal attention and thus tremendous efforts are devoted to developing efficient electrocatalysts that would circumvent the bottlenecks of the electrochemical nitrogen reduction reaction(NRR)like competitive hydrogen evolution reac-tion,poor selectivity of N_(2) on catalyst surface.Herein,we report the synthesis of an oxygen-functionalized boron carbonitride matrix via a two-step pyrolysis technique.The conductive BNCO(1000)architecture,the compatibility of B-2p_(z) orbital with the N-2p_(z) orbital and the charging effect over B due to the C and O edge-atoms in a pentagon altogether facilitate N_(2) adsorption on the B edge-active sites.The optimum electrolyte acidity with 0.1 M HCl and the lowered anion crowding effect aid the protonation steps of NRR via an associative alternating pathway,which gives a sufficiently high yield of ammonia(211.5μg h^(−1) mg_(cat)^(−1))on the optimized BNCO(1000)catalyst with a Faradaic efficiency of 34.7%at−0.1 V vs RHE.This work thus offers a cost-effective electrode material and provides a contemporary idea about reinforcing the charging effect over the secured active sites for NRR by selectively choosing the electrolyte anions and functionalizing the active edges of the BNCO(1000)catalyst.

Optical and Structural Properties of Carbon Nanotube-Rutile Heterostructures

The paper presents a study of the growth and characterization of carbon nanotube-rutile nanocomposites. The heterostructures were obtained with a chemical mixing method. Scanning electron microscope images show that the samples appear as a homogeneous powder of rutile with carbon nanotubes intercalated in interspaces between the TiO2 grains. Characterization by both X-ray photoelectron spectroscopy and cathodo-luminescence analysis show the formation of CO-Ti chemical bonds with a decrease of 0.8 eV in the band gap compared to pure rutile. The consequence of this band gap modification is a strong change in optical properties. Luminescence emission is drastically reduced and absorption in the visible range is increased of about 6% at very low concentration （1%） of carbon nanotubes.

Study of Band Gap of Carbon Nanotube-Titanium Dioxide Heterostructures

The authors present a photoluminescence and UV （ultraviolet）-optical absorbance study on single walled carbon nanotubes CNTs （carbon nanotubes） and TiO2 mixtures. The authors observed variation of△ф = 0.6 eV in optical gap for micrometric anatase and 0.1 eV for nanometric rutile or anatase at a concentration of CNTs of about 1.5 weight %. The large difference in △ф is attributed to differences in dimensions of dioxide grains and in morphology of CNTs/Ti02 composites. Photoluminescence emission is drastically reduced and absorption in the UV range is increased at low CNT concentration for both anatase and rutile phases.

Reliable Ge_(2)Sb_(2)Te_(5) based phase-change electronic synapses using carbon doping and programmed pulses

Hardware electronic synapse and neuro-inspired computing system based on phase change random access memory(PCRAM)have attracted an extensive investigation.However,due to the intrinsic asymmetric reversible phase transition,the defective weight update of PCRAM synapses in aspects of tuning range,linearity and continuity has long required a system-level complexity of circuits and al-gorithms.The cell-level improvements to a great extent may slim the system thus achieving efficient computing.We report in this work the great enhancement of Ge_(2)Sb_(2)Te_(5)(GST)based PCRAM synapses by combining materials engineering and pulse programming.It is found that carbon doping in GST retards the rate of phase changing thus increasing the controllability of the conductance,while non-linear programmable pulse excitations can eventually lead to a reliable synaptic potentiation and depression.A set of improved programmable pulse schemes for spike-timing dependent plasticity was then demonstrated,suggesting its potential superiority in flexible programming and reliable data collection.Our methods and results are of great significance for implementing PCRAM electronic synapses and high-performance neuro-inspired computing.