An efficient and selective production of 5-hydroxymethylfurfural (HMF) from carbohydrates is achieved in the presence of mesoporous AlSiO catalysts in a THF/H₂O–NaCl biphasic system. These mesoporous AlSiO catalysts are prepared by a facile sol–gel method and have tunable acidity. Their acidic sites are characterized and quantified by NH₃-TPD, microcalorimetry of NH₃ adsorption and Py-FTIR, then correlated with the catalytic isomerization and dehydration of glucose to HMF. The detailed studies show that the AlSiO-20 catalyst with a Si/Al ratio of 18 is favorable for HMF production due to its inherently high surface area, high amounts of acid sites and a suitable Brønsted/Lewis acid ratio. Over the AlSiO-20 catalyst, an HMF yield of 63.1% is obtained at 160 °C for 1.5 h in the biphasic THF/H₂O–NaCl medium with 10 wt% glucose in water. Further conducting the amplification experiment 30 times, the HMF yield still reaches 60.2% and the yield has no obvious decline after four catalytic cycles; this is the best result for an amplification experiment of HMF from glucose over a heterogeneous catalyst so far. After separation, HMF can be used for the production of 2,5-furandicarboxylic acid (FDCA) and as high as 95% FDCA yield is obtained over the Pt/C catalyst. Furthermore, the AlSiO catalyst demonstrates excellent activity in the conversion of disaccharides, polysaccharides and even lignocellulosic biomass, indicating it would be a promising catalyst for the conversion of glucose and glucose-based carbohydrates to HMF in industry applications.

This study demonstrated a controllable release properties and synergistic antibacterial actions between orange essential oil (OEO) and silver nanoparticles (AgNPs) incorporated onto cellulose (CL) nanofibers. The preparation of AgNPs attached on CL nanofibers was conducted through multiple processes including the deacetylation process to transform cellulose acetate (CA) nanofibers to CL nanofibers, the in situ synthesis of AgNPs, and the coating of as-prepared silver composite CL nanofibers using OEO solutions with two different concentrations. The success of immobilization of AgNPs onto the surface of CL nanofibers and the incorporation of OEO into the polymer matrix was confirmed by SEM-EDS, TEM, XRD, and FT-IR characterizations. The tensile strength, elongation at break, and Young’s modulus of the nanofibers after each step of treatment were recorded and compared to pristine CA nanofibers. The high antibacterial activities of AgNPs and OEO were assessed against Gram-positive B. subtilis and Gram-negative E. coli microorganisms. The combined effects of two antimicrobials, AgNPs and OEO, were distinctively recognized against E. coli.

We present a design of an ultra-broadband metamaterial absorber in the visible and near- infrared regions. The unit cell structure consists of a single layer of metallic truncated-pyramid resonator-dielectric-metal configuration, which results in a high absorption over a broad wavelength range. The absorber exhibits 98% absorption at normal incidence spanning a wideband range of 417–1091 nm, with >99% absorption within 822–1054 nm. The broadband absorption stability maintains 95% at large incident angles up to 40° for the transverse electric (TE)-mode and 20° for the transverse magnetic (TM)-mode. Furthermore, the polarization-insensitive broadband absorption is presented in this paper by analyzing absorption performance with various polarization angles. The proposed absorber can be applied for applications such as solar cells, infrared detection, and communication systems thanks to the convenient and compatible bandwidth for electronic THz sources.

Graphene oxide addresses increasing interests as a solid acid catalyst working in water for carbohydrate conversion. If there is a general agreement to correlate its unique catalytic performances to its ability to adsorb sugars, the origin of its acidity remains controversial. In this article, we study the acid strength of graphene oxide (GO) prepared by modified Hummers method and that of reduced GO by calorimetry of NH₃ adsorption and by FTIR of pyridine adsorption. Very strong acid sites are detected on GO by calorimetry, while reduced graphene oxide (reGO) is not very acidic. The FTIR of pyridine adsorption shows the prevailing presence of Br∅nsted acid sites and a unique feature, the presence of pyridine coordinated by hydrogen bonds. This exceptionally strong Br∅nsted acidity is tentatively explained by the presence of graphene domains decorated by hydroxyl, carboxylic, or sulfonated groups within the GO sheet, resulting in a high mobility of the negative charges which makes the proton free and explains its strong acidity. Accordingly, only GO is active and selective for native cellulose hydrolysis, leading to 27% yield in glucose. Finally, we show that sugar alcohols cannot be formed directly from cellulose using GO combined with Pt/re-GO under hydrogen, explained by the reduction of oxygenated functions of GO. The instability of the functional groups of GO in a reducing atmosphere is the weak point of this peculiar solid acid.