Advances in Noble Metal-Decorated Metal Oxide Nanomaterials for Chemiresistive Gas Sensors:Overview

Highly sensitive gas sensors with remarkably low detection limits are attractive for diverse practical application fields including real-time environmental monitoring,exhaled breath diagnosis,and food freshness analysis.Among various chemiresistive sensing materials,noble metal-decorated semiconducting metal oxides(SMOs)have currently aroused extensive attention by virtue of the unique electronic and catalytic properties of noble metals.This review highlights the research progress on the designs and applications of different noble metal-decorated SMOs with diverse nanostructures(e.g.,nanoparticles,nanowires,nanorods,nanosheets,nanoflowers,and microspheres)for high-performance gas sensors with higher response,faster response/recovery speed,lower operating temperature,and ultra-low detection limits.The key topics include Pt,Pd,Au,other noble metals(e.g.,Ag,Ru,and Rh.),and bimetals-decorated SMOs containing ZnO,SnO_(2),WO_(3),other SMOs(e.g.,In_(2)O_(3),Fe_(2)O_(3),and CuO),and heterostructured SMOs.In addition to conventional devices,the innovative applications like photo-assisted room temperature gas sensors and mechanically flexible smart wearable devices are also discussed.Moreover,the relevant mechanisms for the sensing performance improvement caused by noble metal decoration,including the electronic sensitization effect and the chemical sensitization effect,have also been summarized in detail.Finally,major challenges and future perspectives towards noble metal-decorated SMOs-based chemiresistive gas sensors are proposed.

A Furan-Substituted Polymeric Hole-Transporting Material for Energy Level Regulation and Less Planarity in Colloidal Quantum Dot Solar Cells

For efficient colloidal quantum dot(CQD)solar cells(CQD-SCs),thiol-passivated p-type CQDs are generally used as a hole-transporting material(HTM);however,there are issues with the control of optoelectrical properties,low thiol passivation rate,and poor morphology with a power conversion efficiency(PCE)of approximately 11%.Although polymeric HTMs have been introduced to address these issues,maximizing efficiency and achieving green-solvent processability and thermal stability for commercialization is necessary.Here,we synthesize a novel benzodifuran(BDF)-based HTM(asy-ranPBTBDF)showing an electron-deficient state,low steric hindrance,and low planarity compared to those of a typical benzodithiophene(BDT)-based HTM(asy-ranPBTBDT).BDF properties lead to deep high occupied molecular orbital(HOMO)levels,closeπ-πstacking,excellent solubility,and amorphous properties related to efficiency,green-solvent processability,and thermal stability.With these benefits,the asy-ranPBTBDF-based CQD-SC showed enhanced open-circuit voltage(Voc)(0.65 V)and PCE(13.29%)compared to those of the asy-ranPBTBDT-based device(0.63 V and 12.22%)in toxic processes with chlorobenzene.The asy-ranPBTBDF-based CQD-SC showed a PCE of 12.51%in a green-solvent process with 2-methylanisole and improved thermal stability at 80℃(83.8%retaining after 24 h)owing to less lateral crystallization than the asy-ranPBTBDT-based device(60.8%retaining after 24 h).

Electromechanical and photoelectric properties of a novel semiconducting Janus InGaSSe monolayer

In recent years,Janus two-dimensional(2D)materials have received extensive research interests because of their outstanding electronic,mechanical,electromechanical,and optoelectronic properties.In this work,we explore the structural,electromechanical,and optoelectronic properties of a novel hypothesized Janus InGaSSe monolayer by means of first-principles calculations.It is confirmed that the Janus InGaSSe monolayer indeed show extraordinary charge transport properties with intrinsic electron mobility of 48139 cm^(2)/(V·s)and hole mobility of 16311 cm^(2)/(V·s).Both uniaxial and biaxial strains can effectively tune its electronic property.Moreover,the Janus InGaSSe monolayer possesses excellent piezoelectric property along both inplane and out-of-plane directions.The results of this work imply that the Janus InGaSSe monolayer is in fact an efficient photocatalyst candidate,and may provide useful guidelines for the discovery of other new 2D photocatalytic and piezoelectric materials.

Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.

Synthesis and Conductivity of a One-dimensional Polymer of a Copper(Ⅱ)-porphyrazine with Sulfur Bridges

A novel conjugated polymer which shows sendconductivity at T < 260K and T >286K and metallic conductivity at 260K < T< 286K was syllthesized by reaction of 2, 3, 5, 6-tetracyano1, 4-dithiin and phthalonitrile with CuCl2.2H2O.

SEMICONDUCTING AND METALLIC POLYMERS:THE FOURTH GENERATION OF POLYMERIC MATERIALS

INTRODUCTIONIn 1976, Alan MacDiarmid, Hideki Shirakawa and I, together with a talented group of graduate students andpost-doctoral researchers discovered conducting polymers and the ability to dope these polymers over the fullrange from insulator to metal. This was particularly exciting because it created a new field of research on theboundary between chemistry and condensed matter physics, and because it created a number of opportunities:

Broadband MMIC Power Amplifier for C-X-Ku-Band Applications

A three-stage MMIC power amplifier operating from 6to 18GHz is fabricated using 0.25μm A1GaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor（PHEMT）.The amplifier isfully monolithic,with all matching,biasing,and DC block circuitry included on the chip.Thepower amplifier has an average power gain of 19dB over 6～18GHz.At operation frequenciesfrom 6 to 18GHz,the output power is above 33.3dBm,and the maximum output power of the MMICis 34.7dBm at 10Ghz.The input return loss is less than-10db and the out-put return is lessthan-6dB over operating frequency.This power amplifier has,to our knowledge,the best powergain flatness reported at C-X-Ku-band applications.

HIGH-ENERGY PROTON IRRADIATION EFFECTS ON GaAs/Ge SPACE SOLAR CELLS

This paper reports the high-energy proton irradiation effects on GaAs/Ge space solar cells. The solar cells were irradiated by protons with energy of 5-20 MeV at fluence ranging from 1×109 to 7×1013 cm-2, and then their electric parameters were measured at AM0. It was shown that the Isc, Voc and Pmax decrease as the proton energy increasing, and the degradation is relative to proton irradiation-induced defect with a level of Ec-0.41 eV in irradiated GaAs/Ge cells.

Semiconducting single-walled carbon nanotubes synthesized by S-doping

An approach was presented for synthesis of semiconducting single-walled carbon nanotubes(SWNTs) by sulfur(S) doping with the method of graphite arc discharge. Raman spectroscopy, UV-vis-NIR absorption spectroscopy and electronic properties measurements indicated the semconducting properties of the SWNTs samples. Simulant calculation indicated that S doping could induce convertion of metallic SWNTs into semiconducting ones. This strategy may pave a way for the direct synthesis of pure semiconducting SWNTs.

Influence of Poly（methyl metacrylate） Addition on Resistive Switching Performance of P3HT/P（VDF-TrFE） Blend Films

Organic semiconducting/ferroelectric blend films attracted much attention due to their electrical bistability and rectification properties and thereof the potential in resistive memory devices. Blend films were usually deposited from solution, during which phase separation oc- curred, resulting in discrete semiconducting phase whose electrical property was modulated by surrounding ferroelectric phase. However, phase separation resulted in rough surface and thus large leakage current. To further improve electrical properties of such blend films, poly（methyl metacrylate） （PMMA） was introduced as additive into P3HT/P（VDF-TrFE） semiconducting/ferroelectric blend films in this work. It indicated that small amount of PMMA addition could effectively enhance the electrical stability to both large electrical stress and electrical fatigue and further improve retention performance. Overmuch PMMA addition tended to result in the loss of resistive switching property. A model on the configuration of three components was also put forward to well understand our experimental observations.

RBC Membrane Camouflaged Semiconducting Polymer Nanoparticles for Near-Infrared Photoacoustic Imaging and Photothermal Therapy

Semiconducting conjugated polymer nanoparticles(SPNs)represent an emerging class of phototheranostic materi-als with great promise for cancer treatment.In this report,low-bandgap electron donoracceptor(DA)-conjugated SPNs with sur-face cloaked by red blood cell membrane(RBCM)are developed for highly e ective photoacoustic imaging and photothermal therapy.The resulting RBCM-coated SPN(SPN@RBCM)displays remarkable near-infrared light absorption and good photosta-bility,as well as high photothermal conver-sion e ciency for photoacoustic imaging and photothermal therapy.Particularly,due to the small size(<5 nm),SPN@RBCM has the advantages of deep tumor penetration and rapid clearance from the body with no appreciable toxicity.The RBCM endows the SPNs with prolonged systematic circulation time,less reticuloendothelial system uptake and reduced immune-recognition,hence improving tumor accumulation after intravenous injection,which provides strong photoacoustic signals and exerts excellent photothermal therapeutic e ects.Thus,this work provides a valuable paradigm for safe and highly e cient tumor pho-toacoustic imaging and photothermal therapy for further clinical translation.

Simple Preparation, Structure and Conductivity of Nickel(Ⅱ) Benzenetricarboxylate Ni_3(BTC)_2·12H_2O

Proton-conductive crystalline metal-organic framework nickel（Ⅱ） benzenetricar- boxylate Ni3（BTC）2A12H2O（MOF-Ni） was prepared by the reaction of nickel（Ⅱ） nitrate and 1,3,5- benzenetricarboxylic（BTC） acid in a mixed solvent of N,N-dimethylformamide（DMF）/C2H5OH/ H2O （1：1：1, ν/ν） at low temperature and short reaction time. It was characterized by thermo- gravimetric analyses （TG）, FT-IR and N2 adsorption-desorption. Single-crystal X-ray diffraction analysis indicated that the complex belongs to monoclinic system, space group C2 with α = 17.407（6）, b = 12.878（5）, c = 6.542（2） A, β = 112.07°, V = 1359.0（8） A^3, Dc = 1.971 g/cm3, μ = 2.166 mm^-1 and Z = 2. Linear polarization resistance （LPR） analysis showed that the complex possesses semiconducting properties.

Semiconducting Mineral Photocatalytic Regeneration of Fe^(2+) Promotes Carbon Dioxide Acquisition by Acidithiobacillus ferrooxidans

Chemoautotrophic organisms have once been excluded from the development of universally applicable CO2 fixation technology due to its low production yields of biomass. In this study, we used Acidithiobacillusferrooxidans （A.f.） as a model chemoautotrophic microorganism to test the hypothesis that exogenetic photoelectrons from semiconducting mineral photocatalysis can enable the regeneration of Fe^2＋ that could be then used by A.f. and support its growth. In a simulated electrochemical system, where exogenetic electrons were provided by an electrochemical approach, an accelerated growth rate of A.f. was observed as compared with that in traditional batch cultivation. In a coupled system, where light-irradiated natural rutile provided the primary electron source to feed A.f., the bacterial growth rate as well as the subsequent CO2 fixation rate was demonstrated to be in a light-dependent manner. The sustaining flow of photogenerated electrons from semiconducting mineral to bacteria provided an inexhaustible electron source for chemoautotrophic bacteria growth and CO2 fixation. This finding might contribute to the development of novel effective CO2 fixation technology.

LPE Growth of InAsPSb on InAs:Melt Composition,Lattice Mismatch and Surface Morphology

The LPE growth of quaternary InAs11-x-yPxSby with x = 0.2 and y = 0.09 on InAs substrate has been studied. This composition is very suitable for the laser and detector applications at about 2.5 μm. We show that in InAsPSb/InAs system there is a determinate relation between the surface morphology and the lattice mismatch of the epi-wafers, by which we can easily control the melt composition to grow high quality hetero-structures. The reason has been discussed. The p-n junctions with fairly good carrier profile have been prepared in this system.

A contrivance of 277 nm DUV LD with B0.313Ga0.687N/B0.40Ga0.60N QWs and AlxGa1–xN heterojunction grown on AlN substrate

In this paper,an ultraviolet C-band laser diode lasing at 277 nm composed of B0.313Ga0.687N/B0.40Ga0.60N QW/QB heterostructure on Mg and Si-doped AlxGa1-xN layers was designed,as well as a lowest reported substitutional accepter and donor concentration up to NA=5.0×10^17 cm^-3 and ND=9.0×10^16 cm^-3 for deep ultraviolet lasing was achieved.The structure was assumed to be grown over bulk AIN substrate and operate under a continuous wave at room temperature.Although there is an emphasizing of the suitability for using boron nitride wide band gap in the deep ultraviolet region,there is still a shortage of investigation about the ternary BGaN in aluminum-rich AIGaN alloys.Based on the simulation,an average local gain in quantum wells of 1946 cm^-1,the maximum emitted power of 2.4 W,the threshold current of 500 mA,a slope efficiency of 1.91 W/A as well as an average DC resistance for the V-I curve of(0.336Ω)had been observed.Along with an investigation regarding different EBL,designs were included with tapered and inverse tapered structure.Therefore,it had been found a good agreement with the published results for tapered EBL design,with an overweighting for a proposed inverse tapered EBL design.

Optimization of heat shield for single silicon crystal growth by using numerical simulation

In integrated circuit-grade single silicon Czochralski growth, the position and material of heat shield are main parameters affecting the heat exchange and crystal growth condition. By optimizing the above parameters, we attempted to increase the growth rate and crystal quality. Numerical simulation proved to verify the results before and after optimization. Through analyses of the temperature and microdefect distribution, it is found that the optimized heat shield can further increase the pulling rate and decrease the melt/crystal interface deflection, increase the average velocity of argon flow from ~2 to ~5 m&middots-1, which is in favor of the transportation of SiO, and obtain the low defects concentration crystal and that the average temperature along the melt-free surface is 8 °C higher than before avoiding supercooled melt effectively. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

InAsSb thick epilayers applied to long wavelength photoconductors

InAs0.052Sb0.948 epilayers with cutoff wavelengths longer than 8 μm were successfully grown on InAs substrates using melt epitaxy （ME）. Scanning electron microscopy observations show that the interface between the epilayers and substrates is flat, indicating the good quality of the epilayers, and the thickness of the epilayers is 40 μm. Photoconductors were fabricated using InAs0.052Sb0.948 thick epilayers grown by ME. Ge optical lenses were set on the photoconductors. At room temperature, the photoresponse wavelength range was 2-10μm. The peak detectivity Dλp reached 5.4 × 10^9 cm-Hz^1/2.W^-1 for the immersed detectors. The detectivity D^＊ was 9.3 × 10^8 and 1.3 × 10^8 cm.Hz^1/2.W^-1 at the wavelength of 8 and 9 μm, respectively. The good performance of the uncooled InAsSb detectors was experimentally validated.

Bifurcation of thermocapillary convection in a shallow annular pool of silicon melt

In order to understand the nature of surface patterns on silicon melts in industrial Czochralski furnaces, we conducted a series of unsteady threedimensional numerical simulations of thermocapillary convections in thin silicon melt pools in an annular container. The pool is heated from the outer cylindrical wall and cooled at the inner wall. Bottom and top surfaces are adiabatic. The results show that the flow is steady and axisymmetric at small temperature difference in the radial direction. When the temperature difference exceeds a certain threshold value, hydrothermal waves appear and bifurcation occurs. In this case, the flow is unsteady and there are two possible groups of hydrothermal waves with different number of waves, which are characterized by spoke patterns traveling in the clockwise and counter-clockwise directions. Details of the flow and temperature disturbances are discussed and number of waves and traveling velocity of the hydro- thermal wave are determined.

Controlling Ion Conductance and Channels to Achieve Synapticlike Frequency Selectivity

Enhancing ion conductance and controlling transport pathway in organic electrolyte could be used to modulate ionic kinetics to handle signals. In a Pt/Poly(3-hexylthiophene-2,5-diyl)/Polyethylene?Li CF3SO3/Pt hetero-junction, the electrolyte layer handled at high temperature showed nano-fiber microstructures accompanied with greatly improved salt solubility. Ions with high mobility were confined in the nano-fibrous channels leading to the semiconducting polymer layer,which is favorable for modulating dynamic doping at the semiconducting polymer/electrolyte interface by pulse frequency.Such a device realized synaptic-like frequency selectivity, i.e., depression at low frequency stimulation but potentiation at high-frequency stimulation.

High-photosensitivity polymer thin-film transistors based on poly(3-hexylthiophene)

Polymer thin-film transistors （PTFTs） based on poly（3-hexylthiophene） are fabricated by the spin-coating process, and their photo-sensing characteristics are investigated under steady-state visible-light illumination. The photosensitivity of the device is strongly modulated by gate voltage under various illuminations. When the device is in the subthreshold operating mode, a significant increase in its drain current is observed with a maximum photosensitivity of 1.7×10^3 at an illumination intensity of 1200 lx, and even with a relatively high photosensitivity of 611 at a low illumination intensity of 100 lx. However, when the device is in the on-state operating mode, the photosensitivity is very low： only 1.88 at an illumination intensity of 1200 lx for a gate voltage of -20 V and a drain voltage of -20 V. The results indicate that the devices could be used as photo-detectors or sensors in the range of visible light. The modulation mechanism of the photosensitivity in the PTFT is discussed in detail.