Tailoring Acid Free-Paper based Analytical Devices (Af-PADs) via radiation assisted modification of cellulose paper.

A novel green fabrication approach is being proposed based on radiation assisted modification of Whatman filter paper 1 (WFP) for development of Acid Free-Paper based Analytical Devices (Af-PADs). Af-PADs exude immense potential as handy tools for on-site detection of toxic pollutants such as, Cr(VI), boron, etc., which have established detection protocols involving acid mediated colorimetric reactions that necessitate external acid addition. The proposed Af-PAD fabrication protocol asserts its novelty through elimination of external acid addition step, making the detection process safer and simpler. To achieve this, poly(acrylic acid) (PAA) was grafted onto WFP via a single step, room temperature process of gamma radiation induced simultaneous irradiation grafting, introducing acidic -COOH groups in the paper thereon. Grafting parameters namely, absorbed dose and concentrations of monomer, homopolymer inhibitor and acid were optimized. The -COOH groups incorporated in PAA-grafted-WFP (PAA-g-WFP) provide localized acidic conditions for colorimetric reactions between pollutants and their sensing agents, anchored on the PAA-g-WFP. Af-PADs loaded with 1,5-diphenylcarbazide (DPC) have been ably demonstrated for visual detection and quantitative estimation of Cr(VI) in water samples using RGB image analysis, with LOD value of 1.2 mg.L-1 and a measurement range comparable to that of commercially available PADs based Cr(VI) visual detection kits.

Plasma polymerized functional supermagnetic Fe3O4 nanostructured templates for laccase immobilization: A robust catalytic system for bio-inspired dye degradation.

Fe3O4 magnetic nanoparticles, synthesized using co-precipitation method, were epoxy functionalized via plasma polymerization of 2,3-epoxypropylmethacrylate (EPMA) precursor. The EPMA-functionalized Fe3O4 nanoparticles (EPMA-f-MN) were employed as templates for facile, one-step covalent immobilization of laccase enzyme at room temperature. Samples were rigorously characterized by FTIR, TGA, SEM, TEM, XRD techniques, while Mössbauer spectroscopy (MöS) and vibrating sample magnetometry (VSM) confirmed the supermagnetic nature of Fe3O4 nanoparticles. Activities of free and immobilized laccase (ImLac) were assayed by spectrophotometrically monitoring the enzymatic reduction of substrate 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) at 420 nm, corresponding to the λmax of ABTS.+. In addition to possessing higher thermal stability and a broader pH tolerance window compared to free laccase, the supermagnetic property of the Fe3O4 renders the ImLac system conveniently recoverable and recyclable. Practical applicability of ImLac towards catalytic degradation of industrial dyes was also ably demonstrated using Acid Blue 193 (AB 193) as a commercially used model textile dye, which belongs to the family of azo dyes. Over 95% degradation of the dye was achieved within a period of 4 hours. ImLac could be used for more than 10 dye degradation cycles with >90 % of retention in enzyme activity.

State of the art in nonthermal plasma processing for biomedical applications: Can it help fight viral pandemics like COVID-19?

Plasma processing finds widespread biomedical applications, such as the design of biosensors, antibiofouling surfaces, controlled drug delivery systems, and in plasma sterilizers. In the present coronavirus disease (COVID-19) situation, the prospect of applying plasma processes like surface activation, plasma grafting, plasma-enhanced chemical vapor deposition/plasma polymerization, surface etching, plasma immersion ion implantation, crosslinking, and plasma decontamination to provide timely solutions in the form of better antiviral alternatives, practical diagnostic tools, and reusable personal protective equipment is worth exploring. Herein, the role of nonthermal plasmas and their contributions toward healthcare are timely reviewed to engage different communities in assisting healthcare associates and clinicians, not only to combat the current COVID-19 pandemic but also to prevent similar kinds of future outbreaks.

Radiation grafted cellulose fabric as reusable anionic adsorbent: A novel strategy for potential large-scale dye wastewater remediation.

A low cost, cellulose based anionic adsorbent has been synthesized at room temperature by single step gamma radiation induced grafting of 4-vinylbenzenesulfonic acid sodium salt (VBSA) onto cellulose using water as solvent. Grafting parameters, namely, radiation dose, monomer concentration, volume/weight ratio, were studied to optimize the radiation grafting process. Poly(VBSA) grafted cellulose (PVBSA-g-cellulose) samples were characterized by grafting yield estimation, Elemental analysis, FTIR, TGA and SEM. The radiation grafted adsorbent was tested for textile dyes removal from aqueous solutions, in batch and continuous flow column operation mode, using Basic Red-29 (BR-29) dye as a model textile dye. Adsorbent with 25% grafting yield exhibited an adsorption capacity of 320 mg.g-1, which was corroborated by the equilibrium adsorption and kinetic studies. The adsorbent was regenerated and demonstrated to be reusable for multiple cycles with minimal attrition losses. The process was successfully upscaled and demonstrated at a semi pilot scale treatment.

Mitigation of Cr(VI) toxicity using Pd-nanoparticles immobilized catalytic reactor (Pd-NICaR) fabricated via plasma and gamma radiation.

Catalytic reduction of Cr(VI) to less toxic Cr(III) form using metal nanoparticles is one of the novel approaches adopted to deal with Cr toxicity. In this work, we report the fabrication of a facile, reusable, and robust Pd nanoparticles-immobilized catalytic reactor (Pd-NICaR) system using green, environment-friendly gamma radiolytic, and plasma polymerization processes. A room temperature, RF-powered plasma polymerization process was employed to functionalize a polyethylene-polypropylene (PE-PP) non-woven matrix with epoxy group containing monomer 2,3-epoxypropyl methacrylate (EPMA). EPMA-functionalized PE-PP (EPMA-f-PE-PP) substrate was subsequently used as a template for in situ generation and immobilization of Pd NPs via gamma radiolytic route. The samples were characterized using FTIR, SEM, XPS, and XRF techniques. The catalytic efficacy of Pd-NICaR towards Cr(VI) reduction, in the presence of formic acid (FA) as a reductant, was investigated spectrophotometrically, and reaction parameters were optimized at reaction temperature of 50 °C and [FA]/[Cr(VI)] = 680 to achieve catalytic reduction efficiency of 99.7% within 10 min in batch process. The system showed excellent reusability (~ 20 cycles) and storage stability (> 30 days) without substantial loss (~ 11%) of activity. Practical applicability of the robust catalytic system towards Cr(VI) toxicity mitigation was established in continuous flow mode using a fixed-bed column reactor.

Cellulose based cationic adsorbent fabricated via radiation grafting process for treatment of dyes waste water.

A cationized adsorbent was prepared from cellulosic cotton fabric waste via a single step-green-radiation grafting process using gamma radiation source, wherein poly[2-(methacryloyloxy) ethyl]trimethylammonium chloride (PMAETC) was covalently attached to cotton cellulose substrate. Radiation grafted (PMAETC-g-cellulose) adsorbent was investigated for removal of acid dyes from aqueous solutions using two model dyes: Acid Blue 25 (AB25) and Acid Blue 74 (AB74). The equilibrium adsorption data was analyzed by Langmuir and Freundlich isotherms, whereas kinetic data was analyzed by pseudo first order, pseudo second order, intra particle diffusion and Boyd's models. The PMAETC-g-cellulose adsorbent with 25% grafting yield exhibited equilibrium adsorption capacities of ∼ 540.0mg/g and ∼ 340.0mg/g for AB25 and AB74, respectively. Linear and nonlinear fitting of adsorption data suggested that the equilibrium adsorption process followed Langmuir adsorption isotherm model, whereas, the kinetic adsorption process followed pseudo-second order model. The multi-linearities observed in the intra-particle kinetic plots suggested that the intraparticle diffusion was not the only rate-controlling process in the adsorption of acid dyes on the adsorbent, which was further supported by Boyd's model. The adsorbent could be regenerated by eluting the adsorbed dye from the adsorbent and could be repeatedly used.

Studies on production of fructo-oligosaccharides (FOS) by gamma radiation processing of microbial levan.

Microbial levan, a natural polymer of fructose, was produced and purified by alcohol precipitation from culture supernatants of Bacillus megaterium type 1 grown in an optimized liquid sucrose medium. GPC analysis showed that the yield of the major fraction of levan having molecular weight ~5000 D increased with increase in sucrose concentration in the broth. Levan subjected to (60)Co-gamma radiation as well as acid hydrolysis was investigated by rheometry, UV-visible spectrophotometry and gel permeation chromatography (GPC) techniques. Unlike most of the polysaccharides, levan powder exhibited good radiation degradation stability up to 150 kGy. Gamma irradiation of 10% levan aqueous solution at 250 kGy yielded 63.0% fructo-oligosaccharide (FOS) with an average molecular weight of 1250 D. Acid hydrolysis of levan using 0.5 N HCl for 60 min treatment time gave rise to the desired FOS with lower yield (23.1%) as compared to that obtained in gamma radiolysis process.