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Pristine titanium dioxide (TiO2) changes color from white to black when it is reduced from TiIV to TiIII by photoexcited electrons. However, the black coloration requires substantial light energy to create, and it vanishes instantaneously upon exposure to air. This work reports the synthesis of surface‐functionalized N‐doped TiO2 nanocrystals that rapidly change color (i.e., within seconds) from whitish to black under low‐power irradiation with excellent color stability in atmospheric conditions. The N‐doping plays a critical role in promoting the surface‐adsorption of polyol groups to stabilize the TiIII species and accelerate the coloration process. A rewritable paper fabricated using these nanocrystals exhibits excellent writing and erasing reversibility in response to UV irradiation and oxygen exposure. The low‐cost, rapid response, excellent reversibility, and good color stability are vital advantages of N‐doped TiO2 nanocrystals for color‐switching applications. [ABSTRACT FROM AUTHOR]

Pristine titanium dioxide (TiO2) changes color from white to black when it is reduced from TiIV to TiIII by photoexcited electrons. However, the black coloration requires substantial light energy to create, and it vanishes instantaneously upon exposure to air. This work reports the synthesis of surface‐functionalized N‐doped TiO2 nanocrystals that rapidly change color (i.e., within seconds) from whitish to black under low‐power irradiation with excellent color stability in atmospheric conditions. The N‐doping plays a critical role in promoting the surface‐adsorption of polyol groups to stabilize the TiIII species and accelerate the coloration process. A rewritable paper fabricated using these nanocrystals exhibits excellent writing and erasing reversibility in response to UV irradiation and oxygen exposure. The low‐cost, rapid response, excellent reversibility, and good color stability are vital advantages of N‐doped TiO2 nanocrystals for color‐switching applications. [ABSTRACT FROM AUTHOR]

Pristine titanium dioxide (TiO2) changes color from white to black when it is reduced from TiIV to TiIII by photoexcited electrons. However, the black coloration requires substantial light energy to create, and it vanishes instantaneously upon exposure to air. This work reports the synthesis of surface‐functionalized N‐doped TiO2 nanocrystals that rapidly change color (i.e., within seconds) from whitish to black under low‐power irradiation with excellent color stability in atmospheric conditions. The N‐doping plays a critical role in promoting the surface‐adsorption of polyol groups to stabilize the TiIII species and accelerate the coloration process. A rewritable paper fabricated using these nanocrystals exhibits excellent writing and erasing reversibility in response to UV irradiation and oxygen exposure. The low‐cost, rapid response, excellent reversibility, and good color stability are vital advantages of N‐doped TiO2 nanocrystals for color‐switching applications. [ABSTRACT FROM AUTHOR]

This work presents the design, development and performance evaluation of new copolymers of N -Vinylcaprolactam and N -acryloyl comonomers as kinetic hydrate inhibitors for a sour gas environment. [Display omitted] • Copolymers were fully characterized as Kinetic Hydrate Inhibitors (KHIs). • New N-Vinylcaprolactam copolymers were designed and synthesized. • KHI performance validated under H 2 S in field simulated sour conditions. • KHI performance depended on copolymer structure. • KHIs with heteroatoms performed better than those with cyclic pendant groups. • Higher ratio of acryloyl monomers showed significantly better KHI performance. Kinetic hydrates inhibitors (KHIs) are mainly water-soluble polymers employed to circumvent gas hydrate formation due to their effectiveness at low dosage, which makes logistics (transport, storage, and pumping) less costly in both onshore and offshore gas operations. Most commercial KHIs contain polymers with amide groups, with poly(N -vinylcaprolactam) P(Vcap) and related copolymers being the most common. In this study, we have synthesized copolymers of N -vinylcaprolactam (Vcap) with N -acryloyl type comonomers and investigated their ability to inhibit the formation of structure-I type gas hydrates under sour environment. Vcap was successfully copolymerized with N -acryloylmorpholine, N -acryloylpyrrolidine, N -Isopropylacrylamide and N -acryloylpiperidine to form a series of low molecular weight copolymers. The compatibility of these copolymers was investigated using cloud point temperature and fouling tests. The performance of all copolymers as KHIs was evaluated with high-pressure rocking cells using a structure-I forming natural gas mixture at 130–140 bar. It was found that KHI performance of copolymers in terms of subcooling temperature exceeded that of the P(Vcap) homopolymer of similar molecular weight. Furthermore, the comonomer with cyclic pendant groups with one heteroatom resulted in a better performance compared to acyclic and cyclic pendant groups with a higher number of heteroatoms. Also, the KHI performance of copolymers increased significantly at higher ratios of acryloyl monomer relative to Vcap. These results describe a facile method to design and develop new copolymers of Vcap as effective KHIs for structure-I type hydrates formed under sour environments. [ABSTRACT FROM AUTHOR]