Recyclable Substrates Research Articles

Ultrasensitive and recyclable superstructure of Au[sbnd]SiO2@Ag wire for surface-enhanced Raman scattering detection of thiocyanate in urine and human serum

Thiocyanate level in the human system can serve as a biomarker to distinguish smokers from non-smokers. Thiocyanate is a potential goitrogen, thus an accurate determination may help to identify lactating mothers with high thiocyanate dosage, thereby preventing the transport of excess SCN− to infants. Surface-enhanced Raman spectroscopy has become a versatile and reliable technique to detect SCN− in different media. However, the conventional surface-enhanced Raman scattering (SERS) substrates used to detect SCN− are often discarded after use. The frequent disposal of such metal nanoparticles is detrimental to the environment and makes the SERS-based detection of SCN− uneconomical. In this study, we present fabrication of a new, ultrasensitive and recyclable SERS substrate, based on an AuSiO2@Ag wire (W) superstructure, to detect SCN− in different media. The hierarchical AuSiO2@AgW substrate was obtained by forming nano-sized patches of SiO2 on micron-sized AgW and anchoring 30 nm-sized gold nanoparticles on the patches with mercaptopropyltrimethoxysilane. This ultrasensitive substrate could detect SCN− at a low concentration of 0.001 μM in water, and 0.01 μM in urine and human serum. In addition, a facile procedure to regenerate and recycle the SCN− bound AuSiO2@AgW platform in different media has been demonstrated. The insight gained in the present study can serve as a promising and powerful method for fabrication of active and recyclable substrates for SERS-based detection of SCN−.

Bilayer composites consisting of gold nanorods and titanium dioxide as highly sensitive and self-cleaning SERS substrates

The authors describe a novel recyclable substrate for highly sensitive surface-enhanced Raman scattering (SERS) studies. It consists of gold nanorods (AuNRs) self-assembled on a TiO2 film and combines the high SERS enhancement of assembled AuNRs with the self-cleaning property of the TiO2 film. It overcomes limitations of conventional SERS substrates such as limited sensitivity, high costs, and poor recyclability. The packing density of the AuNRs on the TiO2 film can be well adjusted, and therefore the SERS enhancement factor of the substrates can be tuned. For the optimized substrate, the SERS enhancement factor is as high as 5.4 × 1010 (Raman laser at 782 nm with 10% of 1.15 mW). This indicates extremely high sensitivity and is promising in terms of single molecule detection. Raman mapping experiments showed the SERS signal to be homogeneously distributed over the whole surface, with a maximal deviation of 3.5%. The SERS activity of this substrate can be restored by degradation of the probe molecules through TiO2 photocatalysis under UV irradiation. In our perception, these findings open a new venue for developing ultra-sensitive and recyclable SERS substrates.

Synthesis and fast transfer of monolayer MoS2 on reusable fused silica.

Atomically thin, two-dimensional materials ranging from superconductors, metals, semiconductors to insulators are emerging as potential candidates for the next-generation digital electronics and optoelectronic applications. Their synthesis on a commonly used substrate and fast transfer to a plenty of desired substrates need to be addressed to meet the industrialization criteria for practical applications. In this study, fused silica, which is amorphous, transparent, and inexpensive, was examined as a substrate for MoS2 synthesis. The MoS2 growth behavior on fused silica and its crystal quality were evaluated. In addition, a novel way was developed to quickly peel off MoS2 from the fused silica surface within 15 s (i.e., etching in an acidic solution to detach the edge and completing the delamination via a capillary force at the interface between air and water). The fused silica could be reused at least three times. Moreover, the produced MoS2 domains showed no obvious degradation of quality. These results support the feasibility of MoS2 synthesis on amorphous and recyclable substrates and also the time-saving transfer for the cost-effective and high-quality production of other two-dimensional materials.

Mesoporous semiconducting TiO2 with rich active sites as a remarkable substrate for surface-enhanced Raman scattering.

Recently, surface-enhanced Raman scattering (SERS) research based on semiconductor TiO2 has received increasing attention. However, the practical application of TiO2 SERS-active substrates has been hampered due to their lower surface performance and detection sensitivity. Here we report a new strategy to enhance the SERS activity of TiO2 nanoparticles (NPs) by means of formation of a mesoporous framework via reductive calcination of polymer coated nanocrystals. The 4-mercaptobenzoic acid (4-MBA) probe molecules on the mesoporous TiO2 substrate exhibit larger SERS enhancement compared with that on the ordinary TiO2 NP substrate; this considerable SERS enhancement mainly stems from the contributions of rich surface active sites of mesoporous TiO2, which can provide more effective adsorption sites for the molecules and promote the charge transfer between the substrate and the adsorbed molecule, and thus remarkably enhance SERS signals. On the mesoporous TiO2, a detection limit of 4-MBA as low as 1 × 10-8 mol L-1 can be achieved, which is the highest sensitivity among those reported for semiconducting substrates and even comparable with those of noble metal substrates. And, it is proved that the mesoporous TiO2 substrates are characterized by high stability and self-cleaning properties, and can be repeatedly used in SERS detection without losing their activity.

Recyclable SERS substrates based on Fe2O3–Ag hybrid hollow microspheres with crumpled surfaces

Fe2O3–Ag hybrid hollow microspheres with crumpled surfaces were prepared as SERS recyclable substrates for 4-aminobenzenethiol (4-ABT) and toxin protein ricin.

Influence of Cadmium and Glucose on Soil Microbial Communities

A laboratory-based simulation of exposure of the soil community in a gray forest soil to cadmium and glucose has been conducted. It was established that while growing in a fertile medium microbial communities isolated from a soil sample contaminated with cadmium have a substantially increased phase of growth delay and there is a reduction in total growth. While analyzing communities by Biolog Ecoplate method, it was found that, as compared to the community isolated from a soil rich in glucose, the community in a soil with cadmium is characterized by significantly lower AWCD, R and H indices, in which the differences increase with time of incubation. Also differences in the pattern and rate of recyclable substrates have been revealed. The resulting data suggest changes in the functional activity of the microbial community in the soil under the influence of cadmium.

Low-cost Au nanoparticle-decorated cicada wing as sensitive and recyclable substrates for surface enhanced Raman scattering

A large-scale, low-cost and three-dimensional biomimetic surface enhanced Raman scattering (SERS) substrate with vast and regular ‘hot spots’ was prepared by the deposition of gold (Au) nanoparticles on the bioscaffold arrays of cicada wings by the electron beam evaporation. Characterizations of the formed three-dimensional Au/cicada wing nanostructure proved that it owns outstanding SERS properties of highly active sensitivity, good uniformity and repeatability. The SERS limit of detection (LOD) for Rhodamine 6G reaching as low as 10−7M, and a Raman enhancement factor being as large as 105 with a relative standard deviation of 10.1% were obtained. More importantly, this substrate has a good recyclability by the simple NaBH4 washing. For the application of Au/cicada wing, thiram was also detected rapidly and quantitatively with a LOD as low as 10−7M. Our findings are beneficial in the application of SERS substrate, allowing quantitative and recyclable detection of trace organic contaminants and making it very promising in the label-free detection of biological molecules.

High performance organic transistor active-matrix driver developed on paper substrate.

The fabrication of electronic circuits on unconventional substrates largely broadens their application areas. For example, green electronics achieved through utilization of biodegradable or recyclable substrates, can mitigate the solid waste problems that arise at the end of their lifespan. Here, we combine screen-printing, high precision laser drilling and thermal evaporation, to fabricate organic field effect transistor (OFET) active-matrix (AM) arrays onto standard printer paper. The devices show a mobility and on/off ratio as high as 0.56 cm2V−1s−1 and 109 respectively. Small electrode overlap gives rise to a cut-off frequency of 39 kHz, which supports that our AM array is suitable for novel practical applications. We demonstrate an 8 × 8 AM light emitting diode (LED) driver with programmable scanning and information display functions. The AM array structure has excellent potential for scaling up.

Multifunctional Fe3O4@TiO2@Au magnetic microspheres as recyclable substrates for surface-enhanced Raman scattering.

Herein, we demonstrate the design and fabrication of multifunctional triplex Fe3O4@TiO2@Au core-shell magnetic microspheres (MSs), which show excellent surface enhanced Raman scattering (SERS) activity with high reproducibility and stability. In addition, due to their excellent catalytic properties, the as-prepared Fe3O4@TiO2@Au magnetic MSs can clean themselves by photocatalytic degradation of target molecules adsorbed onto the substrate under irradiation with visible light, and can be re-used for several cycles with convenient magnetic separability. The influence of the size and distribution of Au nanoparticles (NPs) on the Fe3O4@TiO2 beads is investigated. The optimized samples employing Au NPs of 15 nm size and an areal density of about 2120 Au NPs on every MS show the best SERS activity and recyclable performance. The experimental results show that these magnetic MSs indicate a new route in eliminating the 'single-use' problem of traditional SERS substrates and exhibit their applicability as analytical tools for the detection of different molecular species.

Organic solar cells made with recyclable cellulose substrate

Organic solar cells made with recyclable cellulose substrate

Synthesis and SERS Performance of a Recyclable SERS Substrate Based on Ag NPs Coated TiO2 NT Arrays

Titanium dioxide nanotube arrays (TiO2 NTA) are successfully fabricated via a simple method combine two processes: bottom-up hydrothermal growth of ZnO nanorods and displacement reaction of TiO2 NTA. Silver nanoparticles (Ag NPs) are decorated on TiO2 NTA by in situ Sn2+-mediated reduction of Ag(NH3)2 + to Ag NPs. The structure is characterized by Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscopy (HRTEM). Ag NPs decorated TiO2 NTA (Ag-TiO2) is employed as a SERS-active substrate, which exhibits good SERS intensity and recyclability. The substrate of Ag-TiO2 shows good recyclability as the photo-catalytic property of TiO2, the arrays can clean themselves by photo catalytic degradation of target molecules adsorbed to the substrate under irradiation with UV light into inorganic small molecules.

Recyclable, Flexible, Low‐Power Oxide Electronics

AbstractThe ability to process and dimensionally scale field‐effect transistors with and on paper and to integrate them as a core component for low‐power‐consumption analog and digital circuits is demonstrated. Low‐temperature‐processed p‐ and n‐channel integrated oxide thin‐film transistors in the complementary metal oxide semiconductor (CMOS) inverter architecture are seamlessly layered on mechanically flexible, low‐cost, recyclable paper substrates. The possibility of building these circuits using low‐temperature processes opens the door to new applications ranging from smart labels and sensors on clothing and packaging to electronic displays printed on paper pages for use in newspapers, magazines, books, signs, and advertising billboards. Because the CMOS circuits reported constitute fundamental building blocks for analog and digital electronics, this development creates the potential to have flexible form factor computers seamlessly layered onto paper. The holistic approach of merging low‐power circuitry with a recyclable substrate is an important step towards greener electronics.

In situ controlled growth of well-dispersed gold nanoparticles in TiO2nanotube arrays as recyclable substrates for surface-enhanced Raman scattering

In this paper, well-aligned Au-decorated TiO(2) nanotube arrays with high surface-enhanced Raman scattering (SERS) enhancement were prepared using a facile in situ reduction and controlled growth approach. The gold nanoparticles are well-dispersed and assembled on the mouth surface and the inside of the TiO(2) nanotubes without clogging. The structure and optical properties of the Au-decorated TiO(2) nanotube arrays have been characterized. The Au-decorated TiO(2) nanotube arrays were employed as SERS-active substrates, which exhibit good performance due to long-range coupling between Au nanoparticles, and TiO(2)-assisted enhanced charge-transfer from Au to Rh6G. The SERS activity of the substrates strongly depends on the crystallite size and level of aggregation. The substrates display significant fluorescence quenching ability and uniform SERS responses throughout the whole surface area. Particularly, good recyclability is shown. The photocatalytic property of Au-decorated TiO(2) nanotube array was exploited to recycle the substrate through UV light photocatalytic purification. The experimental results showed that the substrate is featured by high reproducibility and can be used as a highly efficient SERS substrate for multiple detection of different chemical and biological molecules.

Cyclic electroplating and stripping of silver on Au@SiO2 core/shell nanoparticles for sensitive and recyclable substrate of surface-enhanced Raman scattering

A simple and convenient methodology to fabricate silver-coated Au@SiO2 core/shell nanomaterials (Au@SiO2@Ag nanostructures) is developed by cyclic electroplating and stripping of AgNO3 on the surface of Au@SiO2 core/shell nanoparticles, and the proposed nanostructures served as sensitive and reproducible surface-enhanced Raman scattering (SERS) substrates. Silver coverage of nanostructured Au@SiO2@Ag could be easily controlled by electrodeposition time without substrate motion. The Au@SiO2@Ag nanostructures possess a hexagonal array multiplying the hot spots. SERS of the nanostructures was examined at different electrodeposition times using rhodamine B (RdB) as probe molecule and 785 nm excitation. Optimum SERS was observed when silver was electrodeposited at −0.4 V for 1 min. RdB can be detected down to 10−11 M even without the resonance SERS effect, and the enhancement factor was found at 1.03 × 105. Additionally, silver shells could be easily stripped electrochemically when immersed in the H2SO4 solution for rebuilding and recycling the SERS substrates. The results validate the feasibility for quantitative detection of biomolecules in organisms and combine the advantages of recyclability and sensitivity.

Argininosuccinate Synthetase Overexpression in Vascular Smooth Muscle Cells Potentiates Immunostimulant-induced NO Production

Immunostimulants trigger vascular smooth muscle cells (VSMC) to express both the inducible isoform of NO synthase (iNOS) and argininosuccinate synthetase (AS). With constitutively expressed argininosuccinate lyase (AL), AS confers cells with an Arg/Cit cycle that can sustain NO production via continuous regeneration of the NOS substrate, L-arginine (Arg), from the NOS coproduct, L-citrulline (Cit). To assess whether NO synthesis can be rate-limited by Arg recycling, we tested whether AS-overexpressing cells have an enhanced capacity for immununostimulant-induced NO synthesis. Rat VSMC were stably transfected with human AS cDNA in a eukaryotic cell expression vector, driven by a strong viral promoter. AS activity in transfected VSMC exceeded that induced in untransfected cells treated for 24 h with a combination of bacterial lipopolysaccharide and interferon-gamma (LPS/IFN). AS activity was predominantly associated with membranes but was also found in cytosol. Recombinant AS was purified from cytosol and possessed a specific activity exceeding that reported for native AS. Western blotting verified the basal expression of AS antigen in membranes from untreated AS-transfected VSMC and from untransfected VSMC after 24 h exposure to LPS/IFN. Epifluorescence histochemistry revealed a punctate distribution of AS antigen in transfected cells, consistent with a predominant membrane localization. Remarkably, on a per cell basis, LPS/IFN-induced NO production was 3-4-fold greater in AS-transfected cells than untransfected VSMC. In untransfected VSMC, maximal NO production during 48 h required millimolar Arg; notably, Cit was needed at approximately 3-fold higher concentrations than Arg for a comparable NO synthesis rate. In contrast, AS-transfected VSMC utilized Arg and Cit equi-effectively and at much lower concentrations; 100 microM of either precursor supported a maximal rate of NO synthesis for 48 h. The enhanced ability of AS-transfected cells to produce NO, compared with untransfected cells, could not be ascribed to differences in iNOS protein content or LPS/IFN potency for immunoactivation. We conclude that transfection with AS provides a continuous flux of Arg which drives NO synthesis in immunoactivated VSMC. Arg regeneration by AS is rate-limiting to NO synthesis and apparently provides iNOS with a preferred cellular source of Arg. In accord with the reported "channeling" of substrates by urea cycle enzymes, we hypothesize that the Arg/Cit cycle sequesters a discrete pool of recyclable substrate that sustains high-output NO synthesis.

Bioprocessing of sweet sorghum with in situ-produced enzymes.

Enzyme-assisted ensiling (ENLAC), using in situ-produced enzymes from Gliocladium sp. TUB-F-498, preserved 80% of the sugar content of sweet sorghum, and facilitated its extraction by countercurrent diffusion. The in situ enzyme was produced on the extracted sweet sorghum pulp by an 8-d solid substrate fermentation (SSF) with a yield of 4.6 cellulase and 400 IU/g dry wt xylanase. Two percent of the fermented substrate had cellulase and xylanase levels equivalent or superior to levels found in the commercial enzymes Celluclast and Viscozyme Novo at the 0.025% application level in ENLAC. The in situ-production of enzymes on recyclable substrates may reduce bioprocessing costs significantly. In this ENLAC process, the cost of the in situ enzymes is estimated to be about $0.12/MT substrate, compared to $9.5/metric ton (MT) for the commercial enzymes, a cost reduction of nearly 80-fold.

Bicarbonate is a recycling substrate for cyanase.

Cyanase is an inducible enzyme in Escherichia coli that catalyzes bicarbonate-dependent decomposition of cyanate to ammonia and bicarbonate. Previous studies provided evidence that carbamate is an initial product and that the kinetic mechanism is rapid equilibrium random (bicarbonate serving as substrate as opposed to activator); the following mechanism was proposed (Anderson, P. M. (1980) Biochemistry 19, 2282-2888; Anderson, P. M., and Little, R. M. (1986) Biochemistry 25, 1621-1626). (formula; see text) Direct evidence for this mechanism was obtained in this study by 1) determining whether CO2 or HCO3- serves as substrate and is formed as product, 2) identifying the products formed from [14C]HCO3- and [14C] OCN-, 3) identifying the products formed from [13C] HCO3- and [12C]OCN- in the presence of [18O]H2O, and 4) determining whether 18O from [18O]HCO3- is incorporated into CO2 derived from OCN-. Bicarbonate (not CO2) is the substrate. Carbon dioxide (not HCO3-) is produced in stoichiometric amounts from both HCO3- and OCN-. 18O from [18O]H2O is not incorporated into CO2 formed from either HCO3- or OCN-. Oxygen-18 from [18O]HCO3- is incorporated into CO2 derived from OCN-. These results support the above mechanism, indicating that decomposition of cyanate catalyzed by cyanase is not a hydrolysis reaction and that bicarbonate functions as a recycling substrate.

ChemInform Abstract: HLAD‐Catalyzed Oxidations of Alcohols with Acetaldehyde as a Coenzyme Recycling Substrate.

ChemInform Abstract: HLAD‐Catalyzed Oxidations of Alcohols with Acetaldehyde as a Coenzyme Recycling Substrate.

Hlad-catalyzed oxidations of alcohols with acetaldehyde as a coenzyme recycling substrate.

Hlad-catalyzed oxidations of alcohols with acetaldehyde as a coenzyme recycling substrate.

An hypothesis of function for the avian glycogen body: A novel role for glycogen in the central nervous system

Our own and other recent data have led us to hypothesize that the glycogen body, heretofore generally considered to be metabolically inert, may be functionally geared to support the process of myelin formation in the avian central nervous system (CNS). We envision that the abundant glycogen stores in this tissue, unlike those in the liver or in skeletal muscle, can serve as a recyclable substrate for the ultimate production of reducing equivalents that would be available for the synthesis of myelin lipid cholesterol. In addition, it is suggested that such glycogen also may serve as a source of organic acids which might provide alternate substrates to the CNS under conditions of metabolic stress.