Guar Gum/Ethyl Cellulose-Polyvinyl Pyrrolidone Composite-Based Quartz Crystal Microbalance Humidity Sensor for Human Respiration Monitoring

In this work, the guar gum (GG) and the electrospinned ethyl cellulose-polyvinyl pyrrolidone (EC-PVP) nanofibers were used as humidity-sensitive materials for fabricating a quartz crystal microbalance (QCM) sensor. Fourier transform infrared spectroscopy, scanning electron microscopy, water contact angle test, and X-ray photoelectron spectra were used to characterize the synthesized GG/EC-PVP composite material, confirming its successful preparation and good hydrophilicity. The humidity sensitivity experiments were performed at room temperature. The GG/EC-PVP-coated QCM sensor has high sensitivity (55.72 Hz/%RH) and low hysteresis (2.8% RH) in a wide relative humidity range (0-97% RH), short response/recovery time (26/2 s), excellent selectivity, good repeatability, and stability. The combined action of hydrophilic groups and porous structure enhances the humidity sensitivity. The GG/EC-PVP sensor can be used to capture and measure typical breathing patterns in different human basic emotions due to its good performance. Furthermore, a lie-detector system was also designed for judging the lying through detecting the emotional breathing pattern of the subjects.

Hydrothermal Carbonization of Waste Sugarcane Bagasse for the Effective Removal of Emerging Contaminants from Aqueous Solution

Porous carbon spheres were fabricated from sugarcane bagasse using a sustainable hydrothermal carbonization process followed by alkali impregnation inert atmosphere activation. Developed spheres were technically analysed for their chemical science, structural morphology, texture, porosity with respect to size distribution, and thermal degradation. Spheres are functionally enriched with oxygenated groups showing amorphous nature portraying as a smooth surface. After activation, intensity of functional groups is reduced due to reduction reaction by KOH thereby yielding highly rich porous carbon. The active surface area developed on spheres is 111 m2 g-1 holding pores that are mesoporous in nature. Resistance to thermal exposure using TGA showed that decomposition of hemicelluloses followed by cellulose yielded aromatized carbon-rich skeleton through thermal degradation of carboxyl and hydroxyl groups. Developed carbon was found to be effective in removing Ciprofloxacin Hydrochloride from water with maximum adsorption capacity of 110.008 mg g-1. Mechanistic removal followed pseudo-second-order kinetics along with Freundlich mode of adsorption. The presence of carboxylic and hydroxyl groups in porous carbon favoured elimination of CPF from water. The development of HTC-derived carbon helped conserving the energy thereby reducing the cost requirement.

Silver nanomaterials: synthesis and (electro/photo) catalytic applications

In view of their unique characteristics and properties, silver nanomaterials (Ag NMs) have been used not only in the field of nanomedicine but also for diverse advanced catalytic technologies. In this comprehensive review, light is shed on general synthetic approaches encompassing chemical reduction, sonochemical, microwave, and thermal treatment among the preparative methods for the syntheses of Ag-based NMs and their catalytic applications. Additionally, some of the latest innovative approaches such as continuous flow integrated with MW and other benign approaches have been emphasized that ultimately pave the way for sustainability. Moreover, the potential applications of emerging Ag NMs, including sub nanomaterials and single atoms, in the field of liquid-phase catalysis, photocatalysis, and electrocatalysis as well as a positive role of Ag NMs in catalytic reactions are meticulously summarized. The scientific interest in the synthesis and applications of Ag NMs lies in the integrated benefits of their catalytic activity, selectivity, stability, and recovery. Therefore, the rise and journey of Ag NM-based catalysts will inspire a new generation of chemists to tailor and design robust catalysts that can effectively tackle major environmental challenges and help to replace noble metals in advanced catalytic applications. This overview concludes by providing future perspectives on the research into Ag NMs in the arena of electrocatalysis and photocatalysis.

Lignin-Based Porous Supraparticles for Carbon Capture

Multiscale carbon supraparticles (SPs) are synthesized by soft-templating lignin nano- and microbeads bound with cellulose nanofibrils (CNFs). The interparticle connectivity and nanoscale network in the SPs are studied after oxidative thermostabilization of the lignin/CNF constructs. The carbon SPs are formed by controlled sintering during carbonization and develop high mechanical strength (58 N·mm^-3) and surface area (1152 m²·g^-1). Given their features, the carbon SPs offer hierarchical access to adsorption sites that are well suited for CO₂ capture (77 mg CO₂·g^-1), while presenting a relatively low pressure drop (∼33 kPa·m^-1 calculated for a packed fixed-bed column). The introduced lignin-derived SPs address the limitations associated with mass transport (diffusion of adsorbates within channels) and kinetics of systems that are otherwise based on nanoparticles. Moreover, the carbon SPs do not require doping with heteroatoms (as tested for N) for effective CO₂ uptake (at 1 bar CO₂ and 40 °C) and are suitable for regeneration, following multiple adsorption/desorption cycles. Overall, we demonstrate porous SP carbon systems of low cost (precursor, fabrication, and processing) and superior activity (gas sorption and capture).

Honeycomb-like structure-tunable chitosan-based porous carbon microspheres for methylene blue efficient removal

Chitosan (CS) can be used for the preparation of carbon materials with different morphologies due to its excellent properties, but there are no reports on its spherical morphology. In this study, a feasible step-by-step strategy was proposed to fabricate nitrogen-containing chitosan-based porous carbon microspheres (CPCM) in HCl and KOH. The unique spherical morphology and honeycomb-like porous structure of CPCM were accurately regulated. A great quantity of micro/mesopores endowed CPCM an ultra-high specific surface area up to 2463.9 m² g^-1. Moreover, CPCM exhibited an ultra-high maximum adsorption capacity up to 1599.03 mg g^-1 for methylene blue (MB), meanwhile the adsorption process was in well agreement with the Langmuir isotherm and pseudo-second-order kinetic models. It was simultaneously a favorable reusable adsorbent with high regenerative capacity. The high dye adsorption properties suggest that chitosan can be a promising candidate for sewage treatment in the form of carbon microspheres.