Capacitance Polypyrrole‐based Impedimetric Immunosensor for Interleukin‐10 Cytokine Detection

In the present study, we developed a novel label‐free capacitance impedimetric immunosensor based on the immobilization of the human monoclonal antibody anti‐interleukin‐10 (anti‐IL‐10 mAb) onto polypyrrole (PPy)‐modified silicon nitride (Si₃N₄) substrates. The immunosensor was used for the detection of the recombinant interleukin‐10 antigen (rh IL‐10) that may be secreted in patients at the early stage of inflammation. The immunosensor was created by chemical deposition of PPy conducting layer on pyrrole?silane (SPy)‐treated Si/SiO₂/Si₃N₄ substrates (Si/SiO₂/Si₃N₄?SPy), followed by anti‐IL‐10 mAb immobilization through carboxyl‐functionalized diazonium (CMA) protocol and carbodiimide chemistry. The surface characterization and the biofunctionalization steps were characterized by SEM, FTIR and cyclic voltammetry (CV) while the detection process was carried out by using electrochemical impedance spectroscopy (EIS) analyses. The created immunosensor showed two linear fittings (R²=0.999) for the detection of rh IL‐10 within the concentration range from 1–50 pg/mL. It exhibited high sensitivity (0.1128 (pg/mL)^?1) with a very low limit of detection (LOD)=0.347 pg/mL, more particularly, at the low concentration range (1–10 pg/mL). Thus, this developed polypyrrole‐based immunosensor represents a promising strategy for creation of miniaturized label‐free, fast and highly sensitive biosensors for diagnosis of inflammation biomarkers at very low concentrations with reduced cost.     

Formation mechanisms of Si3N4 and Si2N2O in silicon powder nitridation

Commercial silicon powders are nitrided at constant temperatures (1453 K; 1513 K; 1633 K; 1693 K). The X-ray diffraction results show that small amounts of Si₃N₄ and Si₂N₂O are formed as the nitridation products in the samples. Fibroid and short columnar Si₃N₄ are detected in the samples. The formation mechanisms of Si₃N₄ and Si₂N₂O are analyzed. During the initial stage of silicon powder nitridation, Si on the outside of sample captures slight amount of O₂ in N₂ atmosphere, forming a thin film of SiO₂ on the surface which seals the residual silicon inside. And the oxygen partial pressure between the SiO₂ film and free silicon is decreasing gradually, so passive oxidation transforms to active oxidation and metastable SiO(g) is produced. When the SiO(g) partial pressure is high enough, the SiO₂ film will crack, and N₂ is infiltrated into the central section of the sample through cracks, generating Si₂N₂O and short columnar Si₃N₄ in situ. At the same time, metastable SiO(g) reacts with N₂ and form fibroid Si₃N₄. In the regions where the oxygen partial pressure is high, Si₃N₄ is oxidized into Si₂N₂O.     

Growth,characterization and interfacial reaction of magnetron sputtered Pt/CeO2 thin films on Si and Si3N4 substrates

Growth of magnetron sputtered Pt/CeO₂ thin films on Si and Si₃N₄ were characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and X‐ray photoelectron spectroscopy (XPS). Interaction of Pt/CeO₂ films with Si on Si and Si₃N₄ substrates was extensively investigated by XPS. XRD studies show that films are oriented preferentially to (200) direction of CeO₂. XPS results show that Pt is mainly present in +2 oxidation state in Pt/CeO₂/Si film, whereas Pt⁴⁺ predominates in Pt/CeO₂/Si₃N₄ film. Concentration of Pt⁴⁺ species is more than four times on Si₃N₄ substrate as compared with that on Si. Ce is present as both +4 and +3 oxidation states in Pt/CeO₂ films deposited on Si and Si₃N₄ substrates, but concentration of Ce³⁺ species is more in Pt/CeO₂/Si film. Interfacial reaction between CeO₂ and Si substrate is controlled in the presence of Pt. Pt/Ce concentration ratio decreases in Pt/CeO₂/Si₃N₄ film upon successive sputtering, whereas this ratio decreases initially and then increases in Pt/CeO₂/Si film. Copyright © 2015 John Wiley & Sons, Ltd.     

Capacitive Sensing of Amino Acids Using Caliraxene‐Coated Silicon Transducers

The possibility of using capacitance and flat band voltage as measurable quantities for determining amino acids that are neither electroactive nor with strong UV‐vis absorption has been explored. The sensors were fabricated by immobilizing calixarene derivatives on Si/SiO₂/Si₃N₄ transducers. The measurements were made in sulfuric acid media of ca. pH 1 and in physiological buffer of pH 7.4. The different calixarene derivatives showed varying sensitivities to the amino acids ranging from 8 to 137 mV/decade.     

An X-ray photoelectron spectroscopic study of novel SiON glasses

Novel SiON glasses obtained by melting mixtures of crystalline α-SiO₂ and α-Si₃N₄ were investigated by means of X-ray photoelectron spectroscopy (XPS). The incorporation of nitrogen into the SiO₂ network was recently proved by ²⁹Si-MAS-NMR (magic-angle spinning nuclear magnetic resonance) and Si K-XANES (X-ray absorption near edge structure). The Si 2p XPS and the Si KLL XAES (X-ray excited Auger electron spectroscopy) studies of the SiON glasses confirm the formation of mixed structural units (SiO_xN_4-x) by the presence of an additional spectral component energetically located between SiO₂- and Si₃N₄-like signals. The N 1s and O 1s XPS spectra support the conclusion about the incorporation of nitrogen into the SiO₂ network.     

Highly Sensitive Functionalized Conducting Copolypyrrole Film for DNA Sensing and Protein‐resistant

In order to exploit the applications of polypyrrole (PPy) derivatives in biosensors and bioelectronics, the different immobilization mechanisms of biomolecules onto differently functionalized conducting PPy films are investigated. Pyrrole and pyrrole derivatives with carboxyl and amino groups were copolymerized with ω‐(N‐pyrrolyl)‐octylthiol self‐assembled on Au surface by the method of the chemical polymerization to form a layer of the copolymer film, i.e., poly[pyrrole‐co‐(N‐pyrrolyl)‐caproic acid] (poly(Py‐co‐PyCA)) and poly[pyrrole‐co‐(N‐pyrrolyl)‐hexylamine] (poly(Py‐co‐PyHA)), in which the carboxyl groups in poly(Py‐co‐PyCA) were activated to the ester groups. Based on the structure characteristics, the immobilization/hybridization of DNA molecules on PPy, poly(Py‐co‐PyCA) and poly(Py‐co‐PyHA) were surveyed by cyclic voltammograms measurements. For differently functionalized copolymers, the immobilization mechanisms of DNA are various. Besides the electrochemical properties of the composite electrodes of PPy and its copolymers being detected before and after bovine serum albumin (BSA) adsorption, the kinetic process of protein binding was determined by surface plasmon resonance of spectroscopy. Since few BSA molecules could anchor onto the PPy and its copolymers surfaces, it suggests this kind of conducting polymers can be applied as the protein‐resistant material.     

In-situ polymerization for PPy/g-C3N4 composites with enhanced visible light photocatalytic performance

Polypyrrole-modified graphitic carbon nitride composites (PPy/g-C₃N₄) are fabricated using an in-situ polymerization method to improve the visible light photocatalytic activity of g-C₃N₄. The PPy/g-C₃N₄ is applied to the photocatalytic degradation of methylene blue (MB) under visible light irradiation. Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as-prepared composites. Results show that the specific surface area of the PPy/g-C₃N₄ composites increases upon assembly of the amorphous PPy nanoparticles on the g-C₃N₄ surface. Owing to the strong conductivity, the PPy can be used as a transition channel for electrons to move onto the g-C₃N₄ surface, thus inhibiting the recombination of photogenerated carriers of g-C₃N₄ and improving the photocatalytic performance. The elevated light adsorption of PPy/g-C₃N₄ composites is attributed to the strong absorption coefficient of PPy. The composite containing 0.75 wt% PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g-C₃N₄ in 2 h. Moreover, the degradation kinetics follow a pseudo-first-order model. A detailed photocatalytic mechanism is proposed with ·OH and ·O₂^? radicals as the main reactive species. The present work provides new insights into the mechanistic understanding of PPy in PPy/g-C₃N₄ composites for environmental applications.     

Colloidal lithography-based fabrication of suspended nanoporous silicon nitride membranes

Nanoporous membranes provide a basis for constructing non-supported biomembranes, which enable biological processes such as ion and molecule transport through the biomembranes to be investigated under physiological conditions with ease of control. Preparation of such membranes usually requires expensive equipments and extensive experiences. In this paper, we provide a cheap and controllable scheme of high volume fabricating suspended nanoporous Si₃N₄ membranes on a Si wafer by combined colloidal lithography and standard Si fabrication technology including low cost ICP etching and anisotropic Si wet-etch. Si₃N₄ layers are grown on Si wafers. Polystyrene particles of 200-nm-diameter are then monodispersed on the Si₃N₄ layers based on electrostatic repulsions with an average density of 2%. This is followed by Cr masking, ICP etching and Si wet-etch processes to form suspended Si₃N₄ membranes with 200-nm-deep nanopores through the membranes. The well-aligned cylindrical nanopores have a low aspect radio of ca. 0.9, which would be beneficial to forming stable suspended lipid bilayers.     

Membrane oscillator as a chemical sensor

A rhythmic, sustained, stable oscillation was reproducibly observed for a lipid membrane supported by a micropore of a thin membrane tip micropipet (TM pipet). The construction of the TM pipet was accomplished by implementing a microfabrication method that allowed the transference of a Si₃N₄ film with a hole from the Si substrate to the glass tube tip. The main part of the fabrication method is the sealing process: a mix between thermal and amodic bonding. The TM pipet fabrication is described in detail with emphasis on the thermal-anodic bonding process. In addition, a general account of the new device's main features, including various applications, is given.     

Preparation of polypyrrole‐graft‐poly(N‐isopropylacrylamide)/silver nanocomposites from pyrrolyl‐capped macromonomer by AgNO3 and their stimuli responsibility of light emission

Pyrrolyl‐capped poly(N‐isopropylacrylamide) macromonomers (Py‐PNIPAM) were prepared through reversible addition‐fragmentation‐transfer polymerization with benzyl 1‐pyrrolylcarbodithioate as chain‐transfer agent. Polymerizations of Py‐PNIPAM with/without pyrrole using AgNO₃ as oxidizing agent and dimethylforamide as solvent resulted in graft copolymers of polypyrrole‐graft‐poly(N‐isopropylacrylamide) (PPy‐g‐PNIPAM) as well as silver nanoparticles, leading to the formation of PPy‐g‐PNIPAM/silver nanocomposites. The resulting nanocomposites were soluble in water when the content of PPy was low, and when the molar ratio of Py/Py‐PNIPAM increased to 30, the resulting products became insoluble in water. The resulting nanocomposites had special optical properties because of PPy as well as the temperature‐responsible PNIPAM. The chemical structure and composition of nanocomposite were characterized by ¹H nuclear magnetic resonance spectroscopy, gel permeation chromatograms, fourier transform infrared spectroscopy, and X‐ray diffraction. Their optical properties were characterized by UV–vis and fluorescence spectroscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6950–6960, 2008     

Effect of different types of substrate surface treatments on the graphene device performance

Graphene–substrate interface is very crucial for analyzing graphene device performance. In this article, we have shown how the graphene device performance got affected because of different types of substrate surface treatment techniques used before graphene transfer. For fabrication of graphene devices, monolayer chemical vapor deposition (CVD) graphene was transferred onto SiO₂ grown thermally on Si substrate. Forming gas annealed SiO₂/Si shows better device performance as compared with as-grown SiO₂ on Si substrate. A further effect of oxygen plasma and argon plasma cleaning of SiO₂ surface before graphene transfer was investigated. Forming gas annealing improves the performance and plasma treatment degrade the graphene devices' performance.     

共沉淀法和模板法制备均匀负载CeO2/ SiO2的研究

CeO2是三效催化剂(简称TWC)中被广泛应用的涂层材料[1],其优良的储放氧能力(OSC)可以扩大TWC的工作窗口,并可以在与γ-Al2O3的相互作用中提高Al2O3的高温稳定性[2]。在高温下,CeO2会因晶粒迅速长大而失去储放氧能力。为了提高CeO2的高温抗烧结能力,以及进一步提高其氧化还原能力,大部分研究者选择了在CeO2晶格中掺入其他离子的方法,如:Zr4 、Pr3 、La3 等[3￣5],这些离子在CeO2晶格中引入了晶格缺陷,不但稳定了结构,而且提高了氧传输能力。SiO2具有很高的化学稳定性、高比表面及高热稳定性,是载体的理想选择。研究表明,CeO2负载…     

Improved lithium exchange at LiFePO4 cathode particles by coating with composite polypyrrole–polyethylene glycol layers

The polypyrrole–LiFePO₄ composites were synthesized by simple chemical oxidative polymerization of pyrrole (Py) monomer directly on the surface of LiFePO₄ particles. Properties of resulting polypyrrole–LiFePO₄ (PPy-LiFePO₄) samples (especially conductivity) are strongly affected by the preparation technique, polymer additives, and conditions during synthesis. For increasing of PPy-LiFePO₄ conductivity, we used polyethylene glycol (PEG) as additive during polymerization. The electrochemical behavior of the samples was examined by cyclic voltammetry and electrochemical impedance spectroscopy. It was found that PPy/PEG composite polymer decreased the particle to particle contact resistance. Impedance measurements showed that the coating of PPy/PEG significantly decreases the charge transfer resistance of LiFePO₄ electrodes.     

In situ AFM study of electrochemical synthesis of polypyrrole/Au nanocomposite

In this work, in situ AFM measurements with simultaneously electrochemical characterization were developed to study the mechanisms of both polypyrrole (PPy) and PPy/Au composite deposition. The nanoscale information derived from the in situ AFM images associated with theoretical simulation from the measured current–time transient (i–t) reveals that Au nanoparticles with negatively charged carboxylic groups can be the nuclei by both adsorption on the electrode surface and doping on PPy for the polymerization, and thus has faster nucleation and growth rate than Py alone at the early polymerization stage. The PPy/Au deposition shows parallel nucleation processes of Au nanoparticle and Py, and an instantaneous 3D nucleation mode. The work not only provides fundamental insights for PPy/Au nanocomposite deposition process, but also optimization approaches to fabricate a superior PPy/Au film with favorable features for greater potential applications.     

Study of Surface Modification of Nanosize Si3N4 with Macromolecular Coupling Agent LMPB-g-GMA in Different Solvents

A new macromolecular coupling agent, low-molecular-weight polybutadiene liquid rubber (LMPB)-glycidyl methacrylate (GMA), was synthesized using solution polymerization initiated by benzoyl peroxide (BPO). The molecular structure was confirmed by FTIR and NMR. This macromolecular LMPB-GMA was used for surface modification of silicon nitride (Si₃N₄) nanopowder in n-heptane, chloroform, ethyl acetate, and DMF, respectively. LMPB-GMA and modified nano-Si₃N₄ were systematically investigated by FTIR, NMR, TGA, and TEM. The results showed that LMPB-GMA bonded and formed an organic coating layer onto the surface of nanosized Si₃N₄ particles. The polarity of the solvents plays an important role in this process. Strong or weak polar both affect the results. The dosage loading of LMPB-GMA is 12 wt% of nanosized Si₃N₄. Nanosized Si₃N₄ modified in ethyl acetate has better dispersibility and stability than that modified in n-heptane or DMF. TEM pictures also reveal that modified nano-Si₃N₄ possesses good dispersibility.     

Application of a radioactive tracer method to copper migration in Semiconductor Lithography

Radioactive tracer technique was applied to examine the migration of Cu impurity from ArF and KrF photoresists onto silicon-based underlying substrates of Si(100), Si(110), Si(111), poly-Si, SiO₂ and Si₃N₄. The effects of the polymer constituent in the photoresists and the baking temperature were studied. Results showed that the migration ratio of Cu from ArF photoresist was always exceeded that from KrF photoresist, independently of the substrate types and baking temperatures. The benzene ring in the KrF photoresist confined the Cu migration, while the alicyclic constituent in the ArF photoresist could not. The migration process of Cu from the bulk region into the interface region was discussed. The residual solvent in the bulk region influenced the Cu migration. The electronegativity of Cu explained the accumulation of Cu on wafer surface. Simple diffusion model was tried to explain the migration ratios, but the model did not explain it well due to the change of the photoresist medium during baking. A correlation function was proposed to modify the diffusion coefficient for describing the experimental observation of migration ratios.     

Die neuen Schichtsilicate Ba3Si6O9N4 und Eu3Si6O9N4

The New Layer‐Silicates Ba₃Si₆O₉N₄ and Eu₃Si₆O₉N₄ The new oxonitridosilicate Ba₃Si₆O₉N₄ has been synthesized in a radiofrequency furnace starting from BaCO₃, amorphous SiO₂ and Si₃N₄. The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba₃Si₆O₉N₄, space group P3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10⁶ pm³, Z = 1, R1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO₂N₂ tetrahedra forming corrugated layers between which the Ba²⁺ ions are located. Substitution of barium by europium leads to the isotypic compound Eu₃Si₆O₉N₄. Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu₃Si₆O₉N₄, space group P3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10⁶ pm³, R_p = 0.0379, R_F² = 0.0638). The ²⁹Si MAS‐NMR spectrum of Ba₃Si₆O₉N₄ shows two resonances at ?64.1 and ?66.0 ppm confirming two different crystallographic Si sites.     

Chemical Vapor Deposition of Silicon Carbide and Silicon Nitride—Chemistry's Contribution to Modern Silicon Ceramics

Pure silicon carbide and silicon nitride have valuable properties in bulk pore-free form; however, their industrial exploitation has hardly been possible so far. Neither compound can be melted or sintered in pure form; hot pressing or sintering at normal pressure requires the presence of additives; and the reaction-sintering process in which only Si and C or Si and N are employed as additives affords porous materials.–The novel process of chemical vapor deposition has partly overcome the drawbacks of the previous methods. In the new process SiC is produced, e.g., by pyrolysis of CH₃SiCl₃, and Si₃N₄ by reaction of SiCl₄ with NH₃. This technique can also be used for pore filling in objects made of SiC and Si₃N₄ (gas phase impregnation) and for producing extremely fine SiC and Si₃N₄ (gas phase impregnation) and for producing extremely fine SiC and Si₃N₄ powder and SiC monofilaments suitable as components for SiC composites. Moreover, gas phase impregnation can also give fiber composites.     

Interface-directed sol-gel: direct fabrication of the covalently attached ultraflat inorganic oxide pattern on functionalized plastics

For plastic electronics and optics, the fabrication of smooth, transparent and stable crack-free inorganic oxide films (and patterning) on flexible polymeric substrates with strong bonding strength and controllable thickness from nanometers to micrometers is a key but still remains a challenge. Among versatile inorganic oxides, silica oxide film as SiO _x is especially important because this semiconductor material could provide crucial properties in devices or serve as a base layer for further multilayer construction. In this paper, we describe a new interface-directed sol-gel method to fabricate flexible high quality silicon oxide film onto commodity plastics. The resulting crack-free silica film has strong covalent bonding with polymer substrates, homogeneous morphology with ultralow roughness, highly optical transparency, tunable thickness from nm to μm, and easy patterning ability. Such fabrication strategy relies on a novel photocatalytic oxidation reaction by photosensitive ammonium persulfate (APS), which is able to fabricate highly reactive hydroxyl monolayer surface on inert polymeric substrates. This kind of hydroxylated surface could serve as nucleation and growth sites to initiate surface sol-gel process. As a result, well-defined SiO _x film deposition (gelation) occurs, and patterned hydroxylation regions could be easily utilized to induce the formation of patterned oxide film arrays. Our strategy also excludes the requirements of clean room and vacuum devices so as to fulfill low-cost and fast fabrication demands. Two application examples from such high quality SiO _x layer onto plastics are given but should not be limited within these. One is that oxygen permeation rate of SiO _x deposited polymer film decreases 25 times than pristine polymer substrate, which is good for the potential packaging materials. The other one is that silanization monolayer, for example, 3-aminopropyltriethoxysilane (APTES), could be successfully constructed onto silica layer through classical silanization reaction, which is applicable for many potential purposes, for instance, proteins could be accordingly immobilized onto plastic support with effective signal-to-background ratio. Moreover, we further demonstrate that this interface-directed sol-gel strategy is a general method which could be successfully extended to other high quality oxide film fabrication, e.g., TiO₂.     

A spontaneous solid-state NO donor to fight antibiotic resistant bacteria

This study substantiates the chemical origin of a free-radical-driven antibacterial effect at the surface of biomedical silicon nitride (Si₃N₄) in comparison with the long-known effect of oxygen reduction by oxidized TiO₂ at the surface of biomedical titanium alloys. Similar to the antibacterial effect exerted by reactive oxygen species (ROS; i.e., superoxide anions, hydroxyl radicals, singlet oxygen, and hydrogen peroxide) from TiO₂, reactive nitrogen species (RNS), such as nitrous oxide (N₂O), nitric oxide (NO), and peroxynitrite (^?OONO) in Si₃N₄, severely affect bacterial metabolism and lead to their lysis. However, in vitro experiment with gram-positive Staphylococcus epidermidis (S. epidermidis, henceforth) revealed that ROS and RNS promoted different mechanisms of lysis. Fluorescence microscopy of NO radicals and in situ time-lapse Raman spectroscopy revealed different metabolic responses of living bacteria in contact with different substrates. After 48 h, the DNA of bacteria showed complete destruction on Si₃N₄, while carbohydrates of the peptidoglycan membrane induced bacterial degradation on Ti-alloy substrates. Different spectroscopic fingerprints for bacterial lysis documented the distinct effects of RNS and ROS. Spontaneously activated in aqueous environment, the RNS chemistry of Si₃N₄ proved much more effective in counteracting bacterial proliferation as compared to ROS formed on TiO₂, which requires external energy (photocatalytic activation) to enhance effectiveness. Independent of surface topography, the antibacterial effect observed on Si₃N₄ substrates is due to its unique kinetics ultimately producing NO and represents a new intriguing avenue to fight bacterial resistance to conventional antibiotics.