Tannin–Titanium Oxide Multilayer as a Photochemically Suppressed Ultraviolet Filter

Abstract

UV filters can initiate redox reactions of oxygen and water when exposed to sunlight, generating reactive oxygen species (ROS) that deteriorate the products containing them and cause biological damages. This photochemical reactivity originates from the high chemical potential of UV filters, which also determines the optical properties desirable for sunscreen applications. We hypothesize that this dilemma can be alleviated if the photochemical pathway of UV filters is altered to coupling with redox active molecules. Here, we employ tannic acid (TA) as a key molecule for controlling the photochemical properties of titanium dioxide nanoparticles (TiO NPs). TA provides an unusual way for layer-by-layer assembly of TiO NPs by the formation of a ligand-to-metal charge transfer complex that alters the nature of UV absorption of TiO NPs. The galloyl moieties of TA efficiently scavenge ROS due to the stabilization of ROS by intramolecular hydrogen bonding while facilitating UV screening through direct charge injection from TA to the conduction band of TiO. The TiO-TA multilayers assembled in open porous polymer microspheres substantially increased sun protection while dramatically reducing ROS under UV exposure. The assembled structure exhibits excellent in vivo anti-UV skin protection against epidermal hyperplasia, inflammation, and keratinocyte apoptosis without long-term toxicity.

Generic synthesis of small-sized hollow mesoporous organosilica nanoparticles for oxygen-independent X-ray-activated synergistic therapy

“…17) via vacuum impregnation, we employed terephthalic acid (TA) to measure the •OH yield arising from HMOP-TBHP upon X-ray irradiation. 1.0 mol TA can chemically bind with 1.0 mol •OH radical to produce 1.0 mol 2-hydroxyterephthalic acid (TAOH), so the generated concentration of •OH is equal to that of TAOH 49,50 , which can be quantified by measuring its fluorescence emission intensity around 430 nm based on the standard curve (Fig. 4f, g).…”

Tannin-Based Hybrid Materials and Their Applications: A Review

“…These can recombine with an electron subtracted from water to form a hydroxide radical which is then scavenged by the tannin coating. Accordingly, such TiO 2 -TA hybrid can also act as a scavenging agent or harmful free radicals, as demonstrated by Son et al [ 81 ].…”

“…[ 80 ]. ( j ) Mechanism of enhanced UV-resistance by the tannin-mediated radical stabilization [ 81 ].…”

Bipolar Conduction and Giant Positive Magnetoresistance in Doped Metallic Titanium Oxide Heterostructures

“…[ 14 ] Moreover, TiO x is earth‐abundant [ 15 ] and has been widely used in important applications, such as photovoltaics, [ 16 ] photocatalysis, [ 17 ] and ultraviolet absorption. [ 18 ] Particularly, in the rocksalt titanium monoxide (Ti 2+ O), the d xy , d xz , and d yx orbits overlap and form the partially filled t 2g orbit, leading to a unique metallic behavior, [ 19,20 ] different from the other semiconducting TiO x families. Interestingly, rocksalt TiO could have a stoichiometric O/Ti ratio larger than 1, [ 21 ] which could induce hole conduction.…”

“…One promising material is titanium oxide (TiOx), which has tunable oxidation states with the titanium ion charged from 2+ to 4+ [14] . Moreover, TiOx is earth-abundant [15] and has been widely used in important applications, such as photovoltaics [16] , photocatalysis [17] , and ultraviolet absorption [18] . Particularly, in the rocksalt titanium monoxide (Ti 2+ O), the dxy, dxz, and dyx orbits overlap and form the partially filled t2g orbit, leading to a unique metallic behavior [19,20] , different from the other semiconducting TiOx families.…”