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We have developed carbon quantum dots (CQDs) with excellent photoluminescence (PL) properties from macaúba (Acrocomia aculeate) fibers; a widely available cellulosic biomass species of palm trees in South America. As-prepared CQDs showed quasi-spherical morphology with high aqueous solubility and strong excitation-dependent fluorescence behaviour. Interestingly, the CQDs display fluorescence 'turn-off' response with excellent sensitivity toward multi-metal ions including Fe3+, Cu2+ and Hg2+ with very low detection limits of 0.69 μM, 0.99 μM, 0.25 μM, respectively. Notably, ascorbic acid (AA) induced a change in the (turn-off) fluorescence of Fe3+-CQDs, which caused an almost 70% revival of fluorescence (turn-on) by displacing Fe3+ ions. We have also harnessed CQDs as the visible-light-induced photocatalyst to reduce CO2 in water. Especially, the CQDs efficiently promote the photocatalytic reduction of CO2 into methane (CH4) with an evolution rate of 99.8 nmol/g at 436 nm in aqueous conditions. This indicates that the CQDs provide abundant active sites for CO2 adsorption and thus enhance the separation and migration of photo-induced charge carriers that efficiently reduce CO2 into CH4 without any co-catalyst in 100% water. [ABSTRACT FROM AUTHOR]

Engineering keratin plastics from chicken feather wastes is highly attractive from an environmental prospect but challenging due to the influence of extraction routes on the macromolecular keratin features. In this study, the effect of precipitation methods on desired properties of biodegradable keratin films was investigated. Keratin was extracted from an industrial chicken feather waste by sulfitolysis, and further recovered using hydrochloric acid (KHA), citric acid (KCA), sodium chloride (KSC), and acetone (KAT) as precipitating agents. Keratin films containing glycerol at 25 wt% were produced by compression molding. All keratin films were nearly colorless and highly transparent to visible light while exhibiting good UV barrier properties. The KAT and KSC films showed greater ductility (εbreak > 50%) compared with KHA and KCA, which was correlated with broader molecular weight distributions and less crosslinking in the former keratins. Importantly, disulfide bonds created in the processing led to keratin films with low water solubility. Larger surface hydrophobicity was attained from keratin recovered by organic solvent precipitation (KAT). These results advance the understanding of precipitating agents as physicochemical property modifiers of biodegradable keratin films for food packaging and other applications. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is an essential analyte for detecting neurodegenerative diseases and inflammatory processes and plays a crucial role in pharmaceuticals, the food industry, and environmental monitoring. However, conventional H2O2 detection methods have drawbacks such as lengthy analysis times, high costs, and bulky equipment. Non-enzymatic sensors have emerged as promising alternatives to overcome these limitations. In this research, we introduce a simple, portable, and cost-effective non-enzymatic sensor that uses carbon black (CB) and silver nanoparticle-modified δ-FeOOH (Ag/δ-FeOOH) integrated into a disposable electrochemical cell (DCell). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and electrochemical impedance spectroscopy (EIS) confirmed successful CB and Ag/δ-FeOOH immobilization on the DCell working electrode. Electrochemical investigations revealed that the DCell-CB//Ag/δ-FeOOH sensor exhibited an approximately twofold higher apparent heterogeneous electron transfer rate constant than the DCell-Ag/δ-FeOOH sensor, capitalizing on CB's advantages. Moreover, the sensor displayed an excellent electrochemical response for H2O2 reduction, boasting a low detection limit of 22 µM and a high analytical sensitivity of 214 μA mM−1 cm−2. Notably, the DCell-CB//Ag/δ-FeOOH sensor exhibited outstanding selectivity for H2O2 detection, even in potential interferents such as dopamine, uric acid, and ascorbic acid. Furthermore, the sensor has the right qualities for monitoring H2O2 in complex biological samples, as evidenced by H2O2 recoveries ranging from 92% to 103% in 10% fetal bovine serum. These findings underscore the considerable potential of the DCell-CB//Ag/δ-FeOOH sensor for precise and reliable H2O2 monitoring in various biomedical and environmental applications. [ABSTRACT FROM AUTHOR]

We introduce a bifunctional architecture to construct biosensors on solution-blow spinning fiber mats of polylactic acid (PLA) and polyethylene glycol (PEG). PLA/PEG mats acted as substrate for printing electrodes and as matrix to immobilize glucose oxidase (GOx). Prussian Blue nanoparticles (PB) decorated working electrodes to detect H2O2 from enzymatic catalysis at a low applied potential (0 V vs. Ag/AgCl) with detection limit of 0.197 mM. The inexpensive bifunctional device (

A disposable electrochemical immunosensor for on‐site detection of aflatoxin B1(AFB1), one of the most toxic mycotoxins in agri‐food products, was fabricated through a low‐cost cut‐printing method and then modified with zein/polypyrrole(PPy) electrospun nanofibers onto which anti‐AFB1 monoclonal antibodies were immobilized covalently. Fabrication was possible with an innovative and simple approach to adsorb nanofibers onto the working electrode during electrospinning. Electrochemical impedance spectroscopy was employed as the principle of detection, and the data collected with a portable potentiostat were treated with information visualization techniques. The nanostructured immunosensor showed a high sensitivity for AFB1 with a linear detection range from 0.25 to 10 ng mL−1 and a theoretical limit of detection of 0.092 ng mL−1, which is adequate to detect AFB1 in food, according to regulatory agencies. [ABSTRACT FROM AUTHOR]

In the present work the characterization of polyaniline electrosynthesized in propylene carbonate medium in the presence of di- and trichloroacetic acids was performed using different techniques. The electrochemical response by cyclic voltammetry showed redox processes due to the formation of polaron and bipolaron and polymer degradation. The characterization by infrared and UV-visible spectroscopies indicated that the polymers are in the emeraldine salt form with perchlorate anions incorporated. The films produced with both acids in propylene carbonate media presented a compact morphology as observed by scanning electron microscopy. By testing the polyaniline film produced in selected conditions in a lithium battery environment it was found that it presents a high coulombic efficiency, promising for battery applications.