In this work, silica-based luminescent materials containing different contents of carbon were synthesized from rice husk biomass. The intrinsic structure, chemical composition, as well as photoluminescent features were investigated. The results suggest that two forms of carbon, i.e., carbon that is chemically bonded and nonbonded with silica, exist in the structure of the as-prepared amorphous silica nanoparticles, which are believed to be responsible for the origin and quenching of photoluminescence, respectively. The generation of successive localized energy levels within the band gap of silica by the chemically bonded carbon is believed to be the luminescent mechanism. The insight into the photoluminescence of rice husk derived carbon-incorporated silica nanoparticles in this work would be valuable for researchers to further modify the luminescent features for practical applications.

•Photoluminescent mesoporous carbon-doped silica was prepared through the calcination of HCl treated RHs at 550 °C for 6 h.•The mechanism of the high intensity PL is mainly owing to the trapped carbon.•Brunauer–Emmett–Teller (BET) surface area, pore diameter, and pore volume of the carbon-doped silica are 203 m2/g, 6.4 nm and 0.33 cm3/g, respectively.Photoluminescent mesoporous carbon-doped silica with a surface area of 203 m2/g, pore diameter of 6.4 nm and pore volume of 0.33 cm3/g was prepared through the calcination of HCl treated rice husks. The mechanism of the high intensity photoluminescence is mainly owing to the trapped carbon in the silica framework.Photoluminescent mesoporous carbon-doped silica with a surface area of 203 m2/g, pore diameter of 6.4 nm and pore volume of 0.33 cm3/g was prepared through the calcination of HCl-treated rice husks.

Methane can be stored in tea clathrates, that is kinetics of methane clathrate formation can be significantly accelerated (90% saturation uptake in 20 min) by ingredients (polyphenols and saponins) in tea infusions with a volumetric capacity of up to 172 v/v.

Rice husk (RH) biomass is a massive byproduct from rice milling. Applications of RHs have been very limited. Therefore, RHs are often considered as a biowaste. RHs are mainly composed of lignocellulose (ca. 72–85 wt %) and silica (ca. 15–28 wt %). The majority of previous explorations focused on the preparation of silica or other silicon based materials from RHs, while the lignocellulose in RHs was usually burnt and thus wasted. Herein, an approach for comprehensive utilization of RHs has been developed to obtain both lignocellulose and high quality porous silica nanoparticles from RHs. Most of the lignocellulose in RHs was first extracted by dissolving in ionic liquids. The dissolved lignocellulose was subsequently separated and collected. The remaining RH residue after extraction that contains a high concentration of silica was thermally treated to synthesize amorphous porous silica nanoparticles with a high purity and surface area. It was also found that, during the extraction of lignocellulose using ionic liquids, some metal cations (e.g., K+) that generate negative effect for the synthesis of silica can be removed simultaneously, which generates a synergy for this comprehensive approach to make full use of RH biomass. The implication of the present findings is discussed.Keywords: Comprehensive utilization; Ionic liquid; Lignocellulose; Rice husks; Silica

Biogenic silica nanoparticles (25–30 nm in diameter) were synthesized from rice husks. The characterizations revealed that the silica nanoparticles were composed of smaller primary particles (ca. 4.2 nm in diameter), and their clustering led to a porous structure with a surface area of 164 m2/g. Under the controlled melting catalyzed by K+, such silica nanoparticle clusters can gradually fuse to form semicrystalline porous silica frameworks with tunable pore size and structural integrity.Keywords: biomass; hierarchical; porous; rice husk; silica nanoparticles;

Lignosulfonates, which are byproducts of the pulp and paper industry, can be used as promoters for the formation of methane hydrates with a high capacity up to 170 v/v and a high formation rate.

Methane can be stored in tea clathrates, that is kinetics of methane clathrate formation can be significantly accelerated (90% saturation uptake in 20 min) by ingredients (polyphenols and saponins) in tea infusions with a volumetric capacity of up to 172 v/v.

Lignosulfonates, which are byproducts of the pulp and paper industry, can be used as promoters for the formation of methane hydrates with a high capacity up to 170 v/v and a high formation rate.