Surface Functional Layer Research Articles

Nanowire Array Breath Acetone Sensor for Diabetes Monitoring.

Diabetic ketoacidosis (DKA) is a life-threatening acute complication of diabetes characterized by the accumulation of ketone bodies in the blood. Breath acetone, a ketone, directly correlates with blood ketones. Therefore, monitoring breath acetone can significantly enhance the safety and efficacy of diabetes care. In this work, the design and fabrication of an InP/Pt/chitosan nanowire array-based chemiresistive acetone sensor is reported. By incorporation of chitosan as a surface-functional layer and a Pt Schottky contact for efficient charge transfer processes and photovoltaic effect, self-powered, highly selective acetone sensing is achieved. The sensor has exhibited an ultra-wide acetone detection range from sub-ppb to >100 000ppm level at room temperature, covering those in the exhaled breath from healthy individuals (300-800ppb) to people at high risk of DKA (>75ppm). The nanowire sensor has also been successfully integrated into a handheld breath testing prototype, the Ketowhistle, which can successfully detect different ranges of acetone concentrations insimulated breath samples. The Ketowhistle demonstrates the immediate potential for non-invasive ketone monitoring for people living with diabetes, in particular for DKA prevention.

Preparation of PMIA loose nanofiltration membrane with electrostatic layer-by-layer self-assembled for dye/salt filtration

Poly (m-phenylene isophthalamide)-based loose nanofiltration membranes were fabricated by electrospinning and subsequential electrostatic layer by-layer self-assembly methods, and the polyelectrolyte multilayers (PEMs) generated by polyacrylic acid (PAA) and polyethyleneimine (PEI) were adopted to contribute the surface functional layer of nanofiber membranes. The incidences of spraying parameter and nano-SiO2 content on the morphology, chemical constitution and dyes separation performance of PEMs functional layer was investigated, respectively. The results showed that the construction of the PEMs functional layer could obviously enhance the Congo red (CR) filtration efficiency by increasing the rejection from 4.9% to 99.8% and improve the surface hydrophilicity by reducing the water contact angle (WCA) from 90.1° to 51.8°. Nano-SiO2 is introduced as a filler to regulate the assembly density of PEMs functional layers, the prepared PEMs/PMIA/SiO2 membrane achieved a relatively stable permeation flux (22.9 L·m−2·h−1), and maintained high separation efficiency of CR/NaCl solution, revealing the excellent dye desalination performance, which exhibited a potential for the dye/salt wastewater treatment. In particular, we offered a new method to prepare loose nanofiltration (LNF) membranes by electrospinning and electrostatic self-assembly technique with accurate separation of inorganic salts and dye molecules.

Boosting lateral photosensing performances in a P(VDF-TrFE)/Bi2Se3/Si heterojunction induced by surface modification and ferroelectric and pyroelectric effects

A broadband high-sensitivity self-powered PSD is developed by using a Bi2Se3/Si heterojunction and a P(VDF-TrFE) surface functional layer, and analyzed by reducing surface electrical conductivity and coupling ferroelectric and pyroelectric effects.

A Floating Integrated Solar Micro‐Evaporator for Self‐Cleaning Desalination and Organic Degradation

AbstractSafe and clean freshwater harvesting from (organic‐containing) saline or wastewater holds great potential for mitigating water scarcity and pollution, but remains challenging. Herein, a floating photothermal/catalytic‐integrated interfacial micro‐evaporator (g‐C3N4@PANI/PS) is reported as a proof‐of‐concept multifunctional scavenger evaporator system (MSES) to achieve both solar‐driven complete desalination and organic degradation. The spherical porous lightweight polystyrene core, incorporated with a black surface functional layer (g‐C3N4@PANI), enables the hybrid micro‐evaporator to naturally float and thereby collectively self‐assemble under surface tension for interfacial evaporation, which achieves preeminent self‐cleaning for complete salt/solute separation and efficient organic photodegradation under rotation. Remarkably, the floating micro‐evaporator achieves a high solar‐vapor conversion efficiency of ≈90% with high interfacial energy localization and provides abundant active photocatalytic sites on the interface, which is further enhanced by interfacial photothermal cooperation. High photo‐driven degradation efficiencies of 99% for nonvolatile organic compounds (non‐VOC) bisphenol A and 95% for VOC phenol in wastewater are achieved. An outdoor comprehensive solar water treatment test toward organic‐containing high‐salinity sewage verifies the feasibility of MSES for sustainable freshwater harvesting (1.3 kg m−2 h−1), downstream salt recovery, and organic degradation. This strategy may inspire an integrated solution of water scarcity, clean energy, and environmental pollution toward carbon neutrality.

Study on the Influence and Law of Waterproof System Design Factors on the Typical Stress of Bridge Deck Pavement

To improve the structural design rationality of cement concrete bridge deck pavement systems and reduce diseases such as interlayer displacement and rutting in the early stage of bridge deck use, this paper studies the influence and law of the coupling effect of various factors of the waterproof system on the typical stress of bridge deck pavement and determines the best structure combination for the bridge deck pavement structure. A finite element model was established by using commercial software to simulate the mechanical response of different types of waterproof bonding layer, waterproof leveling layer, and impervious structure layer under different parameters. The simulation results show that when the thickness of the pavement layer was 8 cm, the maximum shear stress of the pavement layer occurred in the middle of the wearing course and the junction between layers. When the pavement layers were continuous, the maximum strain of the waterproof bonding layer with the “rubber asphalt + protective plate” structure in the transverse and longitudinal directions was the largest. When the waterproof leveling layer was cement concrete, the structure bore a large amount of stress and easily produced cracks, resulting in water damage. High-density water-based asphalt concrete with a low permeability coefficient can reduce the interlayer shear stress and effectively ensure the interlayer bonding effect. On this basis, the following bridge deck pavement structure was proposed: waterproof system + multifunctional waterproof layer + load-bearing structure layer + surface functional layer.

Study on microstructure and mechanical properties of Ni60 + WC/Ni35/AISI1040 functional surface gradient structure of remanufacturing chute plate for the mining scraper by a low cost high power CO2 laser cladding technique

CO2 laser cladding is a type of green remanufacturing technology, which is of many technical advantages in repairing and remanufacturing industry, especially for some large-scale key mining equipment or parts due to its characteristics of high quality, high efficiency and environmental protection (e.g. energy and material saving). In this paper, the chute plate of coal mining scraper is fixed and remanufactured by CO2 laser cladding technique. Ni60, WC, Ni35, IG55 and other composite powders are selected to design and build the gradient functional structure for chute plate in order to improve the reproduced lifetime. A lot of high power low cost CO2 laser cladding tests are carried out on the matrix material (AISI 1040 steel plate) of old attrite chute plate. The optical microscope, SEM, XRD, microhardness test and wear experiment are adopted to analyze the relationships among the laser cladding process, the overlaying composite material, gradient functional structure and mechanical properties of the remanufacturing scraper’s chute plate. The research results show that laser power and scanning speed are the dominant cladding process parameters, which have a significant influence on the geometric dimension (including width and height), dilution rate and hardness of the deposited layer. These composite powders (especially including the rare earth metals) are the key factor to form the gradient functional structure. The laser cladding Ni60 + WC/Ni35/AISI1040 composite gradient functional structure has a reasonable toughness and strength of the transition layer structure, and a high hardness and wear-resistant surface functional layer, so the fixed and remanufactured product has formed good ductile plasticity and wear resistance properties as a result of the gradient functional structure. The unique Ni60 + WC/Ni35/AISI1040 gradient functional structure makes sure that the chute plate of mining scraper has excellent comprehensive performance, which is satisfied with the service requirements of mechanical parts or equipment in the harsh working environment of the mining industry. This research work provides technological guidance for the fix and remanufacturing chute plate, and achieves the goal of low cost, high efficiency and long life reproduced chute plate of mining scraper.

Laser-induced interfacial state changes enable tuning of the Schottky-barrier height in SiC

We used a 193-nm ArF excimer laser to produce a surface functional layer with a tunable Schottky barrier height (SBH) on the n-type 4H-SiC surface. The SBHs of the laser-modified layer/SiC contact ranged from 0.38 ± 0.05 to 1.82 ± 0.1 eV. We evaluated the I-V characteristics of Schottky barrier diodes (SBDs) and investigated their corresponding nanoscale current transport characteristics across the laser-modified layer/4H-SiC interface. We attributed changes of the interfacial transport properties between Au and SiC to the laser-induced formation of SiOx/Si compounds with oxygen vacancies in the nitrogen-doped (N-doped) defective graphitic structure. Density functional theory calculations suggested that defect oxide in the SiOx/Si decreased the Schottky barrier width and increased the direct electron tunneling current. Furthermore, the Fermi level of the laser-induced N-doped defective graphitic structure shifted towards the conduction band compared with that of pristine graphene, which was also beneficial for reducing the SBH. This study provides a novel understanding of the interfacial interactions of a laser-modified layer on SiC through nanoscale electrical analysis. These findings will be useful for further investigations of SiC-based nano-photoelectric devices.

In situ synthesis of quaternary ammonium on silica-coated magnetic nanoparticles and it’s application for the removal of uranium (VI) from aqueous media

In this study, a novel surface functional layer based on quaternary ammonium is synthesized in situ on the surface of silica coated magnetic nanoparticles. The composite is characterized by XRD, FTIR, SEM, VSM, TGA and zeta potential measurements. Sorption/desorption experiments were performed to evaluate its potential to remove uranium (VI) from aqueous solutions. The results indicated that the new composite has a capacity of ∼87 mg/g with 120 min equilibrium time with good recyclability and strong magnetic response. The pseudo-second order kinetic model was found to fit the experimental data fairly well, the data also suggested the presence of intra-particle diffusion. The adsorption isotherm befitted Langmuir equation. Thermodynamic analysis for the adsorption process was performed and the values of ΔG, ΔH and ΔS are reported.

Synthesis of Multifunctional Fe3O4@TESPA/Eu(NTA)3 Luminescent–Magnetic Nanoparticle and Their Properties

Novel multifunctional Fe3O4@3-(triethoxysilyl)-propylamine (TESPA)/Eu(NTA)3 luminescent–magnetic nanoparticles have been successfully prepared using a modified Stober method. The multifunctional nanoparticles are composed of super-paramagnetic Fe3O4 nanoparticles coated with a surface functional layer (SFL) of TESPA. The SFL is doped with a strong luminescent europium(III) complex with organic ligands 1-(2-naphthoyl)-3,3,3-trifluoroacetone (NTA) (Eu(NTA)3). The obtained Fe3O4@TESPA/Eu(NTA)3 nanoparticles exhibit a high magnetization and red emission with ${^{5}\text{D}_{0}}\to {^{7}}\text{Fn}$ ( $n = 1$ , 2, 3, and 4) transitions of europium(III) ion. These multifunctional luminescent–magnetic nanoparticles show small size, high stability, and excellent dispersity in aqueous solution that suggests promising applications in imaging diagnostic and cancer therapy.

Graphite oxide electrical sensors are able to distinguish single nucleotide polymorphisms in physiological buffers

Atomically flat materials based on graphene present unique opportunities for new technologies and are expected to standardize in near future for their properties based on size, shape and number of atomic layers. On the thicker end of the spectrum, graphite oxides (GrO) present a unique set of material properties in the family of graphene-based 2D materials. In this work, an optimized chemical sourcing and bottom-up nanofabrication approach is utilized for scalable fabrication of a highly sensitive field-effect based biodetector platform, deployable in concentrated liquid medium. GrO based biodetectors displaying very low variations in device-to-device sensor characteristics, were deployed for label-free detection of DNA concentrations from 5 pM to 5 nM in physiological buffer. Furthermore, charge-transport behaviour of GrO devices in electrochemical gate configuration was compared with that of the state-of-the-art graphene based devices. A comparative model for GrO-electrolyte interface is discussed based on the recent developments in this field and elucidate the role surface functional layers play in influencing the field-effect and biosensor performance of GrO based devices. The biodetector platform demonstrated here was able to distinguish analyte DNA strands (20 base pairs) with mismatched nucleotide sequences (containing 1 and 2 base-pair mismatches) from complementary DNA strands. Based on these findings, GrO may serve as cheap and scalable alternative to realize rapid and point-of-care medical diagnostic solutions for screening of diseases related to single nucleotide polymorphisms.

Surface engineering and self-cleaning properties of the novel TiO2/PAA/PTFE ultrafiltration membranes

Immobilization of nano-scaled TiO2 onto polymeric ultrafiltration (UF) membrane offers desirable antifouling and self-cleaning properties to the membrane, which is practical in wastewater purification only if the mechanical strength and long-term self-cleaning durability are realized. This paper reported the surface roughness, mechanical properties, thermal stability, and recycling self-cleaning performance of the novel TiO2/PAA/PTFE UF membranes, which were coated via an innovative plasma-intensified coating strategy. Through careful characterizations, the enhanced engineering properties and the self-cleaning performance were correlated with the surface chemical composition and the creative coating technique. In the recycling photocatalytic self-cleaning tests in photodegradation of methylene blue (MB) solution, about 90 % MB photocatalytic capability of TiO2/PAA/PTFE composite membranes could be recovered with simple hydraulic cleaning combined with UV irradiation. The mechanical properties and thermal stability of TiO2/PAA/PTFE also satisfy the practical application in water and wastewater treatments, despite that the original engineering properties were slightly influenced by PAA grafting and TiO2 coating. The changed properties of the composite UF membrane relative to PTFE are reasonably attributed to the variation of the surface chemical species and chemical bonding, as well as the thickness and evenness of the surface functional layers.

Transparent Nanostructured Titania Coatings with Self- cleaning and Antireflective Properties for Photovoltaic Glass Surfaces

Transparent titania (TiO2) coatings having self-cleaning and antireflection (AR) properties, for application as surface functional layer in cover glasses of photovoltaic (PV) devices, were prepared, characterized and tested. The coating preparation is made by forming first a nanosol through controlled hydrolysis of a tetraisopropyl orthotitanate (TIPT) precursor. The nanosol is then deposited on the glass substrates by dip- coating with a subsequent step of calcination. This work reports the effect of the preparation parameters on both optical and morphological properties of the obtained coatings. The nanostructure and texture of the samples were characterized by X-ray diffraction, UV-vis spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM), while transmittance measurements were carried out to assess the AR properties. Self-cleaning properties were investigated by water contact angle measurements and photocatalytic activity tests. Films with good optical characteristics and high transmittance (T losses < 1 % compared to bare glass) have been obtained at low dip-coating speed (6 mm/s) and high nitric acid concentration (HNO3 0.5 N). The best transmittance values were obtained by calcination of the sample at 500 °C, but a higher amount of acid catalyst in the nanosol synthesis allows to reduce the calcination temperature to 400 °C, while maintaining good optical properties and crystallinity of the thin film.

Characterization of Functional Layers of CdTe Crystals Subjected to Different Surface Treatments

The surface functional layers of commercial detector-grade CdTe crystals are characterized after different surface treatments such as chemical polishing etching in bromine-containing solutions and laser annealing with nanosecond pulses of the second harmonic of a YAG:Nd laser. The effects of etching and laser irradiation with energy density near the melting threshold of CdTe on the optical properties of the CdTe crystal surface are studied using ellipsometry and photoluminescence (PL). The samples after storage in air are also investigated. The intrinsic emission band at 1.58 eV and broad dopant band peaked at 1.45 eV are observed in the PL spectra excited by a semiconductor laser with wavelength of 405 nm at 80 K. The low energy band is associated with carrier recombination at structural defects in the surface layer. The redistribution of the PL band intensities after chemical polishing is found and it is attributed to transformation of the point defect structure and defect formation in the surface region of CdTe. The laser treatment essentially changes the surface state and structure of the surface layer that can be used for effective modification of characteristics of the functional layers of CdTe crystals particularly band bending before formation of electrical contacts.

Research on ERS Steel Deck Pavement Techniques

Abstract Steel bridge deck pavement has been considered as a worldwide engineering problem, especially in China. During the past decade, many famous long-span steel bridges have been built in China, for example, Sutong Yangze River Bridge. However, some serious deterioration on the steel bride deck pavement happened when it was opened to traffic because of the heavy traffic and high temperatures. Based on the analysis on the construction problem of steel deck pavement and special traffic and environmental conditions in China, a new kind of steel deck pavement structure, called epoxy–resin–stone (ERS) steel deck pavement, is presented in this paper. It contains three main layers, i.e., epoxy bonding chips layer (EBCL), resin–asphalt mixture (RA05), and stone mastic asphalt (SMA). EBCL is introduced to act as a waterproof, bonding, and slipping proof layer; RA05 is used as an intermediate layer; and SMA is used as a surface functional layer. Test results and engineering practice show that ERS steel deck pavement has excellent performance and good workability. The technique has been applied in more than 10 steel bridges. It is helpful to solve the difficult steel deck pavement problem in China.

Use of Carbonaceous Polysaccharide Microspheres as Templates for Fabricating Metal Oxide Hollow Spheres

A general method for the synthesis of metal oxide hollow spheres has been developed by using carbonaceous polysaccharide microspheres prepared from saccharide solution as templates. Hollow spheres of a series of metal oxides (SnO2, Al2O3, Ga2O3, CoO, NiO, Mn3O4, Cr2O3, La2O3, Y2O3, Lu2O3, CeO2, TiO2, and ZrO2) have been prepared in this way. The method involves the initial absorption of metal ions from solution into the functional surface layer of carbonaceous saccharide microspheres; these are then densified and cross-linked in a subsequent calcination and oxidation procedure to form metal oxide hollow spheres. Metal salts are used as starting materials, which widens the accessible field of metal oxide hollow spheres. The carbonaceous colloids used as templates have integral and uniform surface functional layers, which makes surface modification unnecessary and ensures homogeneity of the shell. Macroporous films or cheese-like nanostructures of oxides can also be prepared by slightly modified procedures. XRD, TEM, HRTEM, and SAED have been used to characterize the structures. In a preliminary study on the gas sensitivity of SnO2 hollow spheres, considerably reduced "recovery times" were noted, exemplifying the distinct properties imparted by the hollow structure. These hollow or porous nanostructures have the potential for diverse applications, such as in gas sensitivity or catalysis, or as advanced ceramic materials.