Facile SERS screening of melamine in bovine milk with 2D printed AgNPs/glass fabric filter paper as the flexible substrate

Melamine is one of the most frequently detected adulterants in dairy products.The current study proposes a surface-enhanced Raman spectroscopy(SERS)-based analytical tool for fast and reliable screening of melamine in bovine milk.A hand-held Raman spectrometer was used in conjunction with a substrate composed of silver nanoparticles(AgNPs)that was 2D printed onto glass fiber(GF)filter paper.Under optimized conditions,a sensitive and fingerprint-like signal at 674 cm^(-1) was obtained.The AgNPs/GF substrate exhibited high sensitivity to melamine in milk down to 1.9498×10^(-5)mg/mL,which is well below the USA and EU safety limits(2.5×10^(-3)mg/mL).Remarkably,the proposed technology was also highly reproducible,showing spot-to-spot and block-to-block variations below 3.3%and 4.9%at 674 cm^(-1) in Raman intensity,respectively.The characteristic peak intensity and concentration of melamine showed an acceptable linear relationship(R^(2)=0.9909)within the range of 0.0001-1 mg/mL.Overall,the method established in this study can provide an efficient and effective method for the quantitative target screening and detection of melamine in dairy products.

Effect of substrate temperature and oxygen plasma treatment on the properties of magnetron-sputtered CdS for solar cell applications

Cadmium sulfide(CdS)is an n-type semiconductor with excellent electrical conductivity that is widely used as an electron transport material(ETM)in solar cells.At present,numerous methods for preparing CdS thin films have emerged,among which magnetron sputtering(MS)is one of the most commonly used vacuum techniques.For this type of technique,the substrate temperature is one of the key deposition parameters that affects the interfacial properties between the target film and substrate,determining the specific growth habits of the films.Herein,the effect of substrate temperature on the microstructure and electrical properties of magnetron-sputtered CdS(MS-CdS)films was studied and applied for the first time in hydrothermally deposited antimony selenosulfide(Sb_(2)(S,Se)_(3))solar cells.Adjusting the substrate temperature not only results in the design of the flat and dense film with enhanced crystallinity but also leads to the formation of an energy level arrangement with a Sb_(2)(S,Se)_(3)layer that is more favorable for electron transfer.In addition,we developed an oxygen plasma treatment for CdS,reducing the parasitic absorption of the device and resulting in an increase in the short-circuit current density of the solar cell.This study demonstrates the feasibility of MS-CdS in the fabrication of hydrothermal Sb_(2)(S,Se)_(3)solar cells and provides interface optimization strategies to improve device performance.

Growing process and reaction mechanism of electroless Ni-Mo-P film on SiO_2 substrate

The diffusion barrier Ni-Mo-P film for Cu interconnects was prepared on SiO2/Si substrate using electroless method. The surface morphology and composition during the formation process of electroless Ni-Mo-P film were investigated through analyzing samples of different deposition time. Induced nucleation, induced co-deposition, and self-induced growth mechanisms involved in electroless process were confirmed by field-emission scanning electron microscopy （FE-SEM）, energy dispersive spectrometry and atomic force microscopy （AFM）. Firstly, the preceding palladium particles as catalysts induce the nucleation of nickel. Secondly, the nickel particles induce the deposition of molybdenum and phosphorus, which attributes to induced co-deposition. Thirdly, former deposited Ni-Mo-P induces deposition of the latter Ni-Mo-P particles. Moreover, the reaction mechanism was proposed with the oxydate of 3-4PO .

β-Ga_2O_3 thin film grown on sapphire substrate by plasmaassisted molecular beam epitaxy

Monoclinic gallium oxide(Ga_2O_3) has been grown on(0001) sapphire(Al_2O_3) substrate by plasma-assisted molecular beam epitaxy(PA-MBE). The epitaxial relationship has been confirmed to be [010]( 2ˉ01) β-Ga_2O_3||[ 011ˉ0](0001)Al_2O_3 via in-situ reflection high energy electron diffraction(RHEED) monitoring and ex-situ X-ray diffraction(XRD) measurement. Crystalline quality is improved and surface becomes flatter with increasing growth temperature, with a best full width at half maximum(FWHM) of XRD ω-rocking curve of( 2ˉ01) plane and root mean square(RMS) roughness of 0.68° and 2.04 nm for the sample grown at 730 °C,respectively. Room temperature cathodoluminescence measurement shows an emission at ～417 nm, which is most likely originated from recombination of donor–acceptor pair(DAP).

Substrates and interlayer coupling effects on Mo1-xWxSe2 alloys

Two-dimensional(2D) transition metal dichalcogenides alloys are potential materials in the application of photodetectors over a wide spectral range due to their composition-dependent bandgaps. The study of bandgap engineering is important for the application of 2D materials in devices. Here, we grow the Mo1-xWxSe2 alloys on mica, sapphire and SiO2/Si substrates by chemical vapor deposition(CVD) method. Mo1-x Wx Se2 alloys are grown on the mica substrates by CVD method for the first time. Photoluminescence(PL) spectroscopy is used to investigate the effects of substrates and interlayer coupling force on the optical bandgaps of as-grown Mo1-xWxSe2 alloys. We find that the substrates used in this work have an ignorable effect on the optical bandgaps of as-grown Mo1-xWxSe2. The interlayer coupling effect on the optical bandgaps of as-grown Mo1-xWxSe2 is larger than the substrates effect. These findings provide a new way for the future study of the growth and physical properties of 2D alloy materials.

Low-temperature Preparation of Photocatalytic TiO_2 Thin Films on Polymer Substrates by Direct Deposition from Anatase Sol

Anatase TiO2 sol was synthesized under mild conditions （75℃ and ambient pressure） by hydrolysis of titaniumn-butoxide in abundant acidic aqueous solution and subsequent reflux to enhance crystallization. At room temperature and in ambient atmosphere, crystalline TiO2 thin films were deposited on polymethylmethacrylate （PMMA）, SiO2-coated PMMA and SiO2-coated silicone rubber substrates from the as-prepared TiO2 sol by a dip-coating process. SiO2 layers prior to TiO2 thin films on polymer substrates could not only protect the substrates from the photocatalytic decomposition of the TiO2 thin films but also enhance the adhesion of the TiO2 thin films to the substrates. Field-emission type scanning electron microscope （FE-SEM） investigations revealed that the average particle sizes of the nanoparticles composing the TiO2 thin films were about 35-47 nm. The TiO2 thin films exhibited high photocatalytic activities in the degradation of reactive brilliant red dye X-3B in aqueous solution under aerated conditions. The preparation process of photocatalytic TiO2 thin films on the polymer substrates was quite simple and a low temperature route.

Growth and characterization ofβ-Ga_(2)O_(3)thin films grown on off-angled Al_(2)O_(3)substrates by metal-organic chemical vapor deposition

Beta-gallium oxide(β-Ga_(2)O_(3))thin films were deposited on c-plane(0001)sapphire substrates with different mis-cut angles along<>by metal-organic chemical vapor deposition(MOCVD).The structural properties and surface morphology of as-grownβ-Ga_(2)O_(3)thin films were investigated in detail.It was found that by using thin buffer layer and mis-cut substrate technology,the full width at half maximum(FWHM)of the()diffraction peak of theβ-Ga_(2)O_(3)film is decreased from 2°on c-plane(0001)Al_(2)O_(3)substrate to 0.64°on an 8°off-angled c-plane(0001)Al_(2)O_(3)substrate.The surface root-mean-square(RMS)roughness can also be improved greatly and the value is 1.27 nm for 8°off-angled c-plane(0001)Al_(2)O_(3)substrate.Room temper-ature photoluminescence(PL)was observed,which was attributed to the self-trapped excitons formed by oxygen and gallium vacancies in the film.The ultraviolet-blue PL intensity related with oxygen and gallium vacancies is decreased with the increas-ing mis-cut angle,which is in agreement with the improved crystal quality measured by high resolution X-ray diffraction(HR-XRD).The present results provide a route for growing high qualityβ-Ga_(2)O_(3)film on Al_(2)O_(3)substrate.

Investigation on plasma-sprayed ZrO_2 thermal barrier coating on nickel alloy substrate

The thermal barrier coatings with NiCrAlY alloy bonding layer, NiCrAlY Y 2O 3 stabilized ZrO 2 transition layer and Y 2O 3 stabilized ZrO 2 ceramic layer are prepared on nickel alloy substrates using the plasma spray technique. The relationship among the composition, structure and property of the coatings are investiga ted by means of optical microscope, scanning electronic microscope and the experiments of thermal shock resistance cycling and high temperature oxidation resistance. The results show that the structure design of introdu cing a transition layer between Ni alloy substrate and ZrO 2 ceramic coating guarantees the high quality and properties of the coatings; ZrO 2 coatings doped with a little SiO 2 possesses better thermal shock resistance and more excellent hot corrosion resistance as compared with ZrO 2 coating materials without SiO 2 ;the improvement in performance of ZrO 2 coating doped with SiO 2 is due to forming more dense coating structure by self closing effects of the flaws and pores in the ZrO 2 coatings.

Fast Growth of Highly Ordered TiO2 Nanotube Arrays on Si Substrate under High-Field Anodization

Highly ordered TiO_2 nanotube arrays(NTAs) on Si substrate possess broad applications due to its high surfaceto-volume ratio and novel functionalities, however, there are still some challenges on facile synthesis. Here, we report a simple and cost-effective high-field(90–180V) anodization method to grow highly ordered TiO_2 NTAs on Si substrate,and investigate the effect of anodization time, voltage, and fluoride content on the formation of TiO_2 NTAs. The current density–time curves, recorded during anodization processes, can be used to determine the optimum anodization time. It is found that the growth rate of TiO_2 NTAs is improved significantly under high field, which is nearly 8 times faster than that under low fields(40–60 V). The length and growth rate of the nanotubes are further increased with the increase of fluoride content in the electrolyte.

Theoretical Study on the Reaction of PCl_3/H_2 on Silicon Substrate Surface

The reaction mechanism of PCl3/H2 on silicon substrate surface （simulated by Si4 cluster） was investigated with Density Functional Theory （DFT） at the B3LYP/6-311G^＊＊ level. On silicon substrate, PCl3 firstly undergoes dissociative adsorption, and then the adsorption product reacts with H2 via a four-step multi-channel mode to give the final product PSi4 cluster. The geometries at each stationary point were fully optimized. The possible transition states were determined by vibrational mode analysis and IRC verification. And finally, the main reaction channel was given.

Growth, Microstructure and Electrochemical Properties of RF Sputtered LiMn₂O₄Thin Films on Au/Polyimide Flexible Substrates

LiMn2O4 thin films are deposited on gold coated polyimide flexible substrates using RF magnetron sputtering technique maintained at a moderate substrate temperature of 300℃. The films exhibited characteristic peaks with predominant (111) orientation representing cubic spinel structure of Fd3m symmetry with an evaluated lattice parameter of 8.199 ?. The surface topography of films exhibited pyramidal shaped grains oriented vertical to the substrate surface with root mean square surface roughness of 90 nm. The Pt/LiMn2O4 electrochemical cell in aqueous region exhibited two step de-insertion and insertion kinetics of Li ion during oxidation and reduction reaction with an initial discharge capacity of 36 μAh?cm_2?μm_1.

Self-powered solar-blind photodiodes based on EFG-grown(100)-dominant β-Ga_(2)O_(3) substrate

We report the edge-defined-film-fed(EFG)-grown β-Ga_(2)O_(3)-based Schottky photodiodes.The device has a reverse leakage current of ~nA and a rectified ratio of ~10^(4) at ±5 V.In addition,the photodiode detector shows a dark current of 0.3 pA,a photo-responsivity(R) of 2.875 mA/W,a special detectivity(D*) of 10^(10) Jones,and an external quantum efficiency(EQE) of 1.4% at zero bias,illustrating a self-powered operation.This work may advance the development of the Ga_(2)O_(3)-based Schottky diode solar-blind photodetectors.

Effects of Substrate Temperatures on the Structure and UV-shielding Properties of TiO_2-CeO_2 Films Deposited on Glass by Radio-frequency Magnetron Sputtering

TiO2-CeO2 films were deposited on soda-lime glass substrates at varied substrate temperatures by rf magnetron sputtering using 40% molar TiO2-60% molar CeO2 ceramic target in Ar：O2=95：5 atmosphere.The structure,surface composition,UV-visible spectra of the films were measured by scanning electron microscopy and X-ray diffraction,and X-ray photoelectron spectroscopy,respectively.The experimental results show that the films are amorphous,there are only Ti^4＋ and Ce^4＋ on the surface of the films,the obtained TiO2-CeO2 films shou a good uniformity and high densification,and the films deposited on the glass can shield ultraviolet light without significant absorpition of visible light,the films deposited on substrates at room temperature and 220℃ absorb UV effectively.

Preparation of CeO_2 Buffer Layer on Cube Textured Nickel Substrate by Reactive Sputtering

The buffer layer CeO2 films were grown on cube textured metallic Ni substrates by using reactive magnetrun sputtering. Ar/H2 mixed atmosphere, which effectively inhibited the formation of NiO, was used as pre-depositing gas before CeO2 films were grown in Ar and 02. At 700 ℃ under the total pressure of 26 Pa,the pure c-axis orientation tilm was obtained. X-ray θ-2θscan, pole figure and φ-scan were used to observe the microstructure of the buffer layer. The resuits show that CeO2 film has strong cube texture and the FWHM is 9°. In addition, the CeO2 film is dense and crack-free.

High-Quality Bi_2Te_3 Single Crystalline Films on Flexible Substrates and Bendable Photodetectors

Recently, great efforts have been made in the fabrication of arbitrary warped devices to satisfy the requirement of wearable and lightweight electronic products. Direct growth of high crystalline quality films on flexible substrates is the most desirable method to fabricate flexible devices owing to the advantage of simple and compatible preparation technology with current semiconductor devices, while it is a very challenging work, and usually amorphous, polycrystalline or discontinuous single crystalline films are achieved. Here we demonstrate the direct growth of high-quality Bi2 Te3 single crystalline films on flexible polyimide substrates by the modified hot wall epitaxy technique. Experimental results reveal that adjacent crystallites are coherently coalesced to form a continuous film, although amounts of disoriented crystallites are generated due to fast growth rate. By inserting a quartz filter into the growth tube, the number density of disoriented crystallites is effectively reduced owing to the improved spiral interaction. Furthermore, flexible Bi2 Te3 photoconductors are fabricated and exhibit strong near-infrared photoconductive response under different degrees of bending, which also confirms the obtained fexible films suitable for electronic applications.

Epitaxial CeO_2 Thin Films on (1102) Sapphire Substrate

Epitaxiai CeO_2 thin films have ben grown on in situ (1102) sapphire subetrate by planar target rf mag-netron sputtering methed. The CeO_2 thin films have perfect (002) orientation with CeO_2(001)∥Al_2O_3(1102). The X-ray 2θ-θ diffraction, ω scan, Φ scan and electron channelling pattern (ECP) shown that thefilms liave high lattice perfection. The relation of growth conditions and film structure was also studied. Thespudering gas presure and subetrate temperature are the most important parameters preparing fer high qualitybeO_2 films.

High-T_c Superconducting Films with J_c 1.5×10~6 A·cm^(-2) Prepared on Substrate ZrO_2 (100) by DC-magnetron Sputtering

Values of critieal eurrent densityJ。exceeding lo6A·em一2 at 77K and zerofield have been rePorted for thinmagnetlcfllnls ofYBaoCu:O,on sinZle ervstal substrates ofSrTIO:〔l一3)and一MgO(4,5)by manvfeseafCnerS.bllt tne rCSUltS OIJ、)IU一A’cm一IorY廿tU Illms on suoslrale 01 slngleerystal ZrO:(100)have not been found out inPublished PaPers 50 far.Owing to themierostrueture eharacters and highJ。ofYBCO films by contrast with bulk it 15 themost Possible to aPPly the fllms to eleetronicfield first.Therefore it 15 more signifieant toimProve values ofjcsubstrate with betterPIOCeSSJc>

AN ABNORMAL BEHAVIOR OF NANO-CRYSTALLINE IN SiO_2 SUBSTRATE

Temperature dependence of the hyperfine field of Fe nanocrystalline in SiO2matrix prepared by using an ion implantation and subsequent heat treatment can not be described by a formula for the isolated Fe nanocrystalline.The large stresses or chemical bond force to which interface atoms may be subjected lead to increase effective anisotropic constant. In addition a little concentration of oxygen atoms contained in the crystalline might enhance the hyperfine field.

Heterogeneous Growth of ZnO Crystal on GaN/Al_(2)O_(3) Substrate

Hydrothermal(HT)ZnO substrates were usually used as seeds for the vapor growth of ZnO crystals.In this work,ZnO bulk crystals were grown using the relatively low-cost GaN/AlOsubstrates as seeds by chemical vapor transport(CVT).With the increase of growth time,the dislocation densities in the crystal decreased from about 1×10^(6) to 6×10^(3) cm^(-2).The carrier concentration decreased from 1.24×10^(19) to 1.57×10^(17)cm^(-3),while the carrier mobility increased from 63.8 to 179 cm^(2)/(V·s).The optical transmittance in the VIS-NIR wavelength increased significantly in combination with the decreasing dislocation densities and impurity concentrations.The dislocation lines and related fast diffusion paths gradually decreased and disappeared in the late growth stage,and the crystal qualities were consequently improved.The experimental results show that the properties of as-grown ZnO crystals are comparable with bulk ZnO grown on the HT substrates to some extent.The GaN/Al_(2)O_(3) seeds may have a potential application value in the industrial production of ZnO single crystals.

Effects of Substrate Temperature on Properties of Transparent Conductive Ta-Doped TiO_2 Films Deposited by Radio-Frequency Magnetron Sputtering

Ta-doped titanium dioxide films are deposited on fused quartz substrates using the rf magnetron sputtering technique at different substrate temperatures. After post-annealing at 550℃ in a vacuum, all the films are crystallized into the polycrystalline anatase TiO2 structure. The effects of substrate temperature from room temperature up to 350℃ on the structure, morphology, and photoelectric properties of Ta-doped titanium dioxide films are analyzed. The average transmittance in the visible region（400-800 nm） of all films is more than 73%.The resistivity decreases firstly and then increases moderately with the increasing substrate temperature. The polycrystalline film deposited at 150℃ exhibits a lowest resistivity of 7.7 × 10^-4Ω·cm with the highest carrier density of 1.1×10^21 cm^-3 and the Hall mobility of 7.4 cm^2·V^-1s^-1.