A new design of colorimetric films using bacterial cellulose nanocrystals derived from nata de coco for sensing volatile organic compounds.

In this work, bacterial cellulose (BC) derived from Nata de Coco is a polysaccharide material, and it is further processed into bacterial cellulose nanocrystal (BCNC) via acid hydrolysis. Then BCNC is doped with transition metals to enhance its amine/hydrogen sulfide response. Therefore, the aim of this study is to investigate the use of transition metals as indicators to detect amine and hydrogen sulfide gas for efficiently monitoring food spoilage. BCNCs were treated with various concentrations of silver nitrate (AgNO3) and copper sulfate pentahydrate (CuSO4·5H2O). Then the dropwise addition of ascorbic acid was applied to reduce Ag+ and Cu2+ to Ag0 (silver nanoparticle) and Cu0 (copper nanoparticle), which refer to red brown and red wine colors, respectively. The results indicated that BCNC/Ag nanoparticles were spherical, while BCNC/Cu nanoparticles exhibited a rod-like structure. XRD results also presented the incorporation of Ag and Cu nanoparticles, as confirmed by both crystallography structures. Furthermore, UV-Vis spectra showed the adsorption bands at 422-430 nm and 626-629 nm, belonging to Ag and Cu nanoparticles. After H2S and ammonia gas exposure, BH/Ag and BH/Cu films turned black from brown and red. In conclusion, transition metal-doped BCNCs exhibit potential for innovative food spoilage gas sensors.

Ratiometric electrochemical lateral flow immunoassay for the detection of Streptococcus suis serotype 2.

An electrochemical lateral flow immunoassay (eLFIA) strip with high reproducibility was developed to rapidly and accurately detect Streptococcus suis serotype 2. This proposed strip was fabricated by integrating ratiometric electrochemical detection and LFIA (R-eLFIA). The R-eLFIA exhibited excellent reproducibility, which was improved by 3.8 times compared to a single electrode. A dual-working screen-printed graphene electrode (SPGE) was designed by tuning the working electrode with electroactive species in the biosensing system. Ferrocene carboxylic acid (Fc) was used as a signal probe, and sunset yellow (SY) at one working electrode was used as an internal reference signal to provide a built-in correction for reducing the effects of inherent background current. S. suis serotype 2-specific antibodies were immobilized on a nitrocellulose membrane of LFIA, which is located on the position of Fc-SPGE. In the presence of the analyte, an immunocomplex formed on the region of Fc-SPGE, causing a decrease in Fc current while SY current remained constant. The current ratio's decrease was proportional to S. suis serotype 2's concentration. Under optimization, this biosensor showed good linearity in the range of 102-1010 CFU/mL with a limit of detection of 10 CFU/mL and achieved a rapid detection time (15 min). Moreover, the R-eLFIA biosensor exhibited excellent reproducibility and high selectivity and was applied in human serum samples. Thus, this study successfully matched the advantages of the ratiometric strategy and LFIA and has great potential to be used as an effective tool for rapidly detecting S. suis serotype 2 in clinical samples.

Hybrid Photo- and Thermal Catalyst System for Continuous CO2 Reduction.

Heterogeneous thermal catalytic processes are vital for industrial production of fuels, fertilizers, and other chemicals necessary for sustaining human life. However, these processes are highly energy-intensive, requiring a vast consumption of fossil fuels. An emerging class of heterogeneous catalysts that are thermally driven but also exhibit a photochemically enhanced rate can potentially reduce process energy intensity by partially substituting conventional heat (where fossil fuels are needed) with solar energy. Such catalyst systems have yet to be practically utilized. Here, we demonstrate a compact electrically heated photo- and thermal annular reactor module to reduce CO2 to CO, via the reverse water gas shift reaction. A first-principles-based design approach was taken in developing a SiO2 on an Al photo- and thermal catalyst system for the model photo- and thermal indium oxide hydroxide (In2O3-x(OH)y) catalysts. A 5-fold light enhancement in the CO production rate and over 70 h of stable CO production were achieved. This represents the highest light enhancement effect reported for this model photocatalyst to date. The reactor presented herein allows continuous operation and a significant reduction of 31% in heater power consumption when provided with an additional 2 suns of irradiation, demonstrating the strong photo- and thermal-harvesting performances of the catalyst system developed in this work.

Towards Solar Methanol: Past, Present, and Future.

This work aims to provide an overview of producing value-added products affordably and sustainably from greenhouse gases (GHGs). Methanol (MeOH) is one such product, and is one of the most widely used chemicals, employed as a feedstock for ≈30% of industrial chemicals. The starting materials are analogous to those feeding natural processes: water, CO2, and light. Innovative technologies from this effort have global significance, as they allow GHG recycling, while providing society with a renewable carbon feedstock. Light, in the form of solar energy, assists the production process in some capacity. Various solar strategies of continually increasing technology readiness levels are compared to the commercial MeOH process, which uses a syngas feed derived from natural gas. These strategies include several key technologies, including solar-thermochemical, photochemical, and photovoltaic-electrochemical. Other solar-assisted technologies that are not yet commercial-ready are also discussed. The commercial-ready technologies are compared using a technoeconomic analysis, and the scalability of solar reactors is also discussed in the context of light-incorporating catalyst architectures and designs. Finally, how MeOH compares against other prospective products is briefly discussed, as well as the viability of the most promising solar MeOH strategy in an international context.