Block Copolymer Derived Electrospun Mesoporous Nanofibers

In this study we have successfully demonstrated the synthesis of porous polymer / polymer derived carbon nanofibers from two block copolymer systems. In first case poly(styrene - block - methylmethacrylate) (PS - b - PMMA) of three different molecular weights were used to produce nanofibers with different morphologies. Various electrospinning parameters such as applied potential difference, distance between spinneret and co llector, flowrate and the concentration of polymer in an organic solvent we re optimized to get fine fibers. Fibers thus obtained were annealed to undergo a microphase separation followed by UV exposure treatment which causes crosslinking of one phase and at the same time degradation of another phase. The degraded phase was then etched out using a weak acid to obtain the desired porosity . The porous fibers thus obtained were characterized using field emission electron microscopy ( FESEM ) and fouri er transmission infrared spectroscopy ( FTIR ) . Wettability studies were also carried out for the different morphologies. In second case a blend of a homopolymer (polyacrylonitrile (PAN)) and a copolymer ( poly( a crylonitrile - block - methylmethacrylate) (PAN - b - P MMA )) was electrospu

IIT researchers develop materials to detect hydrogen gas leaks with high sensitivity

The research team has synthesized a semiconductor material that can be used as a sensitive detector of hydrogen gas. The work by the IIT-Hyderabad and IIT-Jodhpur team would help in the development of reliable and robust hydrogen gas sensors with high sensitivity and quick response, for domestic as well as industrial applications

Block Copolymer Derived Electrospun Mesoporous Nanofibers

In this study we have successfully demonstrated the synthesis of porous polymer / polymer derived carbon nanofibers from two block copolymer systems. In first case poly(styrene - block - methylmethacrylate) (PS - b - PMMA) of three different molecular weights were used to produce nanofibers with different morphologies. Various electrospinning parameters such as applied potential difference, distance between spinneret and co llector, flowrate and the concentration of polymer in an organic solvent we re optimized to get fine fibers. Fibers thus obtained were annealed to undergo a microphase separation followed by UV exposure treatment which causes crosslinking of one phase and at the same time degradation of another phase. The degraded phase was then etched out using a weak acid to obtain the desired porosity . The porous fibers thus obtained were characterized using field emission electron microscopy ( FESEM ) and fouri er transmission infrared spectroscopy ( FTIR ) . Wettability studies were also carried out for the different morphologies. In second case a blend of a homopolymer (polyacrylonitrile (PAN)) and a copolymer ( poly( a crylonitrile - block - methylmethacrylate) (PAN - b - P MMA )) was electrospu

Electrospun Mesoporous poly(Styrene-Block-methylmethacrylate) Nanofibers as Biosensing Platform: Effect of Fibers Porosity on Sensitivity

The present work demonstrates the use of mesoporous nanofibers for the enhanced analytical performance of electrochemical biosensor. By exploiting the phase separation property of the block copolymers, a simple three‐step process was used to generate the porosity in the nanofibers. Here we present the effect of the porosity on the sensing ability of the electrospun PS‐b‐PMMA nanofibers. The functional groups present on the nanofiber surface were characterized using DPV. The nanofibers modified electrode showed a large decrease in the oxidation current with the increase in the pH from 4.2 to 6.8 for the anionic redox couple whereas the change in the current is negligible for a neutral redox couple, this suggested the presence of ‐COOH groups. A one‐step process was used for the immobilization of biotin. There were about 35.5 % and 66.6 % decrease in the redox current for the as‐spun and porous nanofibers after functionalization respectively which indicate the presence of a high amount of active sites in the porous nanofibers. Finally, the sensor response was studied using streptavidin (1μg/ml–1fg/ml) as a model analyte. CV studies showed a 2.7‐fold increase whereas DPV showed a 6‐fold increase in the sensitivity for the porous nanofibers as compared to the as‐spun nanofibers

Electrospun Mesoporous Poly(Styrene‐Block‐Methyl‐ Methacrylate) Nanofibers as Biosensing Platform: Effect of Fibers Porosity on Sensitivity

The present work demonstrates the use of mesoporous nanofibers for the enhanced analytical performance of electrochemical biosensor. By exploiting the phase separation property of the block copolymers, a simple three‐step process was used to generate the porosity in the nanofibers. Here we present the effect of the porosity on the sensing ability of the electrospun PS‐b‐PMMA nanofibers. The functional groups present on the nanofiber surface were characterized using DPV. The nanofibers modified electrode showed a large decrease in the oxidation current with the increase in the pH from 4.2 to 6.8 for the anionic redox couple whereas the change in the current is negligible for a neutral redox couple, this suggested the presence of ‐COOH groups. A one‐step process was used for the immobilization of biotin. There were about 35.5 % and 66.6 % decrease in the redox current for the as‐spun and porous nanofibers after functionalization respectively which indicate the presence of a high amount of active sites in the porous nanofibers. Finally, the sensor response was studied using streptavidin (1μg/ml–1fg/ml) as a model analyte. CV studies showed a 2.7‐fold increase whereas DPV showed a 6‐fold increase in the sensitivity for the porous nanofibers as compared to the as‐spun nanofibers

Pencil Graphite Electrodes as Platform for Enzyme and Enzyme-Like Protein Immobilization for Electrochemical Detection

Carbon-based electrodes are being used widely nowadays for biosensor applications, primarily owing to their good electrical conductivity and ease of functionalization. At the same time, the increasing demand for the low cost, disposable and the ease of availability for the do-it-yourself assemblies have provided an opportunity to look beyond conventional carbon materials for electrochemical analysis. In recent time, the pencil lead, entitled as the pencil graphite has been used as an electrode for the enzyme-based electrochemical biosensors. The review highlights the various aspects involved in using pencil graphite electrode (PGE) as a working electrode. This includes the various pretreatment strategies used, which is the first step toward the effective surface functionalization, followed by strategies used for the immobilization of the functional nanomaterials and the enzymes and finally, the integration of the PGE with different types of sensor assemblies. A comprehensive discussion on the latest development in this area also suggests future perspectives based on PGE to develop low-cost point-of-care diagnostics

Investigation of poly(vinyl) alcohol-gellan gum based nanofiber as scaffolds for tissue engineering applications

The objective of the present work was to fabricate poly(vinyl alcohol)-gellan gum nanofiber (PG-NFs) based scaffolds for tissue engineering applications. PG-NFs were fabricated via electrospinning and were characterized using scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis. Physical properties including water solubility, swelling behavior, contact angle, apparent porosity, biodegradation, and conductivity studies were performed. SEM micrographs displayed long, uniform and randomly oriented PG-NFs of average diameter of 158 ± 23 nm with an interconnected three-dimensional network structure and FTIR study showed gellan gum interaction with PVA through hydrogen bonding. The degradation assay confirmed that as fabricated PG-NFs were stable in the aqueous medium without any significant weight loss. The apparent porosity of PG-NFs was 40%, and conductance was 126.93 pS. The PG-NFs was also proven to be non-toxic and biocompatible by supporting the growth of murine embryonic stem cells (ESCs), similar as control, upon culturing on the same. In summary, stability of PG-NFs in the aqueous medium and significant growth of ESCs in vitro on such 3D nanofibrous scaffolds make it a promising material for various tissue engineering applications

Synthesis of amphiphilic poly(ethylene glycol)-block-poly(methyl methacrylate) containing trityl ether acid cleavable junction group and its self-assembly into ordered nanoporous thin films

A strategy for the synthesis of well defined poly(ethylene glycol)-block-poly(methyl methacrylate) diblock copolymers containing trityl ether acid cleavable junctions is demonstrated. This approach is achieved by using a combination of poly(ethylene glycol) macroinitiator containing a trityl ether end group, which is susceptible to acid cleavage, and atom transfer radical polymerization technique. The trityl ether linkage between blocks can be readily cleaved in solution or in solid phase under very mild acid condition, which has been confirmed by 1H NMR. These diblock copolymers have been used to successfully fabricate nanoporous thin films by acid cleavage of trityl ether junction followed by complete removal of poly(ethylene glycol) block. The fabricated nanoporous thin films may have a wide range of application such as Recessed Nanodisk-array electrode (RNE) or as a template to fabricate nanoelectrode array for senor applications

Poly(styrene-block-methylmethacrylate) derived electrospun mesoporous nanofibers

Mesoporous materials are of great interest in fields of catalysis, biosensing, gas sensing and adsorption due to their high specific surface area as compared to macroporous materials and lower pore diffusion resistance when compared to microporous materials. The microphase separation property of block copolymers can be used to obtain mesoporous materials by selectively etching one of its polymer blocks. In this study, we have successfully demonstrated the synthesis of mesoporous poly (styrene-block-methylmethacrylate) (PS-b-PMMA) nanofibers using electrospinning. Morphology of these PS-b-PMMA fibers obtained by electrospinning depends on a number of process as well as solution parameters which were tuned to obtain long uniform and continuous fibers as confirmed by field emission electron microscopy. The nanofibers thus obtained were thermally annealed to assist the phase separation. Later the fibers were exposed to ultraviolet radiation followed by etching with a weak acid to remove the degraded polymer block leading to mesoporous PS-b-PMMA nanofibers, as confirmed by transmission electron microscopy. We also demonstrate the direct synthesis of porous PS-b-PMMA fibers driven by the rapid vaporization of the highly volatile solvent. A comprehensive study of the effect of electrospinning solvent and annealing and etching conditions on the specific surface area, porous structure including pore volume and pore size distribution is carried out using the nitrogen adsorption-desorption isotherms and the small angle X-ray scattering (SAXS). We also analyzed the mesoporous nature of PS-b-PMMA nanofibers using fractal dimension analysis