Anchoring Gated Mesoporous Silica Particles to Ethylene Vinyl Alcohol Films for Smart Packaging Applications

Utilizing Imine Bonds to Create a Self-Gated Mesoporous Silica Material with Controlled Release and Antimicrobial Properties

In recent years, silica nanomaterials have been widely studied as carriers in the field of antibacterial activity in food. Therefore, it is a promising but challenging proposition to construct responsive antibacterial materials with food safety and controllable release capabilities using silica nanomaterials. In this paper, a pH-responsive self-gated antibacterial material is reported, which uses mesoporous silica nanomaterials as a carrier and achieves self-gating of the antibacterial agent through pH-sensitive imine bonds. This is the first study in the field of food antibacterial materials to achieve self-gating through the chemical bond of the antibacterial material itself. The prepared antibacterial material can effectively sense changes in pH values caused by the growth of foodborne pathogens and choose whether to release antibacterial substances and at what rate. The development of this antibacterial material does not introduce other components, ensuring food safety. In addition, carrying mesoporous silica nanomaterials can also effectively enhance the inhibitory ability of the active substance.

Dual Stimuli-Responsive Copper Nanoparticles Decorated SBA-15: A Highly Efficient Catalyst for the Oxidation of Alcohols in Water

In the present work, a temperature and pH-responsive hybrid catalytic system using copolymer-capped mesoporous silica particles with metal nanoparticles is proposed. The poly(2-(dimethylamino)ethyl methacrylate)(DMAEMA)-co-N-tert-butyl acrylamide) (TBA)) shell on mesoporous silica SBA-15 was obtained through free radical polymerization. Then, copper nanoparticles (CuNPs) decorated SBA-15/copolymer hybrid materials were synthesized using the NaBH₄ reduction method. SBA-15 was functionalized with trimethoxylsilylpropyl methacrylate (TMSPM) and named TSBA. It was found that the CuNPs were uniformly dispersed in the mesoporous channels of SBA-15, and the hybrid catalyst exhibited excellent catalytic performance for the selective oxidation of different substituted benzyl alcohols in water using H₂O₂ as an oxidant at room temperature. The dual (temperature and pH-) responsive behaviors of the CuNPs/p(DMAEMA-co-TBA)/TSBA catalyst were investigated using the dynamic light scattering technique. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of the products was identified using ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. The catalyst showed excellent catalytic activity toward the oxidation of alcohol to aldehyde in an aqueous medium below the lower critical solution temperature (LCST) and pKa values (7–7.5) of the copolymer. The main advantages of the hybrid catalyst, as compared to the existing catalysts, are outstanding alcohol conversion (up to 99%) for a short reaction time (1 h), small amount of the catalyst (5 mg), and good recyclability equal to at least five times.

Mesoporous Silica Micromotors with a Reversible Temperature Regulated On-Off Polyphosphazene Switch

The incorporation of an extraneous on-off braking system is necessary for the effective motion control of the next generation of micrometer-sized motors. Here, the design and synthesis of micromotors is reported based on mesoporous silica particles containing bipyridine groups, introduced by cocondensation, for entrapping catalytic cobalt(II) ions within the mesochannels, and functionalized on the surface with silane-derived temperature responsive bottle-brush polyphosphazene. Switching the polymers in a narrow temperature window of 25-30 °C between the swollen and collapsed state, allows the access for the fuel H₂ O₂ contained in the dispersion medium to cobalt(II) bipyridinato catalyst sites. The decomposition of hydrogen peroxide is monitored by optical microscopy, and effectively operated by reversibly closing or opening the pores by the grafted gate-like polyphosphazene, to control on demand the oxygen bubble generation. This design represents one of the few examples using temperature as a trigger for the reversible on-off external switching of mesoporous silica micromotors.