We study nonlinear Cerenkov radiation generated from a nonlinear photonic crystal waveguide where the nonlinear susceptibility tensor is modulated by the ferroelectric domain. Nonlinear polarization driven by an incident light field may emit coherently harmonic waves at new frequencies along the direction of Cerenkov angles. Multiple radiation spots with different azimuth angles are simultaneously exhibited from such a hexagonally poled waveguide. A scattering involved nonlinear Cerenkov arc is also observed for the first time. Cerenkov radiation associated with quasi-phase matching leads to these novel nonlinear phenomena.

Maintaining the high activity of an enzyme is a fundamental requirement to widen the application of metal–organic frameworks (MOFs) in the biotechnology, biosensor, and biomedicine fields. However, it is still challenging to monitor and understand an MOF environment-related activity for an enzyme. Here, we developed a MOFs-in-nanochannels configuration for broadening the biocatalytic activity of an enzyme in MOFs on demand. ZIF-8 [Zn­(mim)2, Hmim = 2-methylimidazolated] grown in TiO2 nanochannels is used as the platform, and cytochrome C (CytC) is used as a model enzyme encapsulated in ZIF-8. The enzymatic catalytic process converts 2,2′-azino-bis­(3-ethylbenzothiazoline-6-sulfonate) (ABTS) to a positively charged product (ABTS+). On the basis of current–voltage properties, the change of ion transport characteristics in nanochannels can be monitored with time. The ZIF-8 encapsulating CytC molecules not only exhibit a significantly enhanced enzymatic activity in a wide temperature region (37–80 °C) but also have remarkably long storage stability at room temperature. The results of quantum mechanical calculation indicate that the Fe–S bond of CytC is inclined to break in the environment of ZIF-8 owing to the confinement effect of the MOF structure, favorable for enzymatic catalysis. The MOFs-in-nanochannel configuration provides an innovative and label-free design for the onsite monitoring of catalytic activity of an enzyme in MOFs, which holds great potential in constructing biosensing platforms with remarkable performance and stability.

The low penetration depth of UV light in mammalian tissue is the critical limitation for the use of TiO2-based photocatalysis in biomedical applications. In this work, we develop an effective near-infrared (NIR)-active photocatalytic platform that consists of a shell structure of upconversion nanocrystals decorated on a core of Au/dark-TiO2. The heart of this system is the strong photocatalytic activity in the visible region enabled by the gold surface-plasmon resonance on dark TiO2 (D-TiO2). Simulation and experiment demonstrate for an optimized Au/D-TiO2 combination a highly enhanced light absorption in the visible range. Using ampicillin sodium (AMP) as model drug, we exemplify the effective use of this principle by demonstrating a NIR light-triggered photocatalytic payload release. Importantly, the photocatalytically generated reactive oxygen species can effectively inactivate AMP-resistant bacteria strains, thus maintaining an antibacterial effect even after all drug is released. Overall, we anticipate that the here-introduced NIR-light-active photocatalytic cascade can considerably widen TiO2-based photocatalysis and its applications into the infrared range.

Silver orthophosphate (Ag3PO4) is a low-band-gap photocatalyst that has received considerable research interest in recent years. In this work, the magnetic Ag3PO4/TiO2/Fe3O4 heterostructured nanocomposite was synthesized. The nanocomposite was found to exhibit markedly enhanced photocatalytic activity, cycling stability, and long-term durability in the photodegradation of acid orange 7 (AO7) under visible light. Moreover, the antibacterial film prepared from Ag3PO4/TiO2/Fe3O4 nanocomposite presented excellent bactericidal activity and recyclability toward Escherichia coli (E. coli) cells under visible-light irradiation. In addition to the intrinsic cytotoxicity of silver ions, the elevated bactericidal efficiency of Ag3PO4/TiO2/Fe3O4 can be largely attributed to its highly enhanced photocatalytic activity. The photogenerated hydroxyl radicals and superoxide ions on the formed Ag/Ag3PO4/TiO2 interfaces cause considerable morphological changes in the microorganism's cells and lead to the death of the bacteria.

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WO3 nanoparticles loaded in TiO2 nanotube arrays, fabricated by a chemical bath deposition (CBD) technique in combination with a pyrolysis process, is uniform and the diameter can be easily adjusted by the deposition times. The resultant hybrid nanotubes array shows a multistage coloring electrochromic response at different potential bias. The formation of a 3‐dimensional WO3/TiO2 junction promotes unidirectional charge transport due to the one‐dimensional features of the tubes, which leads to the significant positive‐shift onset potential of the cathodic reaction (ion insertion) and the highly increased proton storage capacity. Compared to non‐decorated nanotube arrays, the enhanced electrochromic properties of longer lifetime, higher contrast ratio (bleaching time/coloration time), and improved tailored electrochromic behavior could be achieved using the composite films.

Large-area nanostructured noble-metal films ͑Ag, Pt, and Au͒ can be deposited with high yields and various morphologies on silicon formed between the semiconductor and the noble metal by means of a galvanic cell. It is shown that the morphology of Ag, which is different from that of Pt and Au, can be influenced markedly by the deposition conditions. Distinctive surface-enhanced Raman-scattering features are observed on these Ag films.

Electrochromic materials are widely used in smart windows. An ideal future electrochromic window would be able to control visible light transmission, tune building's heat conversion of near-infrared (NIR) solar radiation, and reduce attacks by microorganisms. To date, most of the reports have primarily focused on visible-light transmission modulation using electrochromic materials. Herein, we report the fabrication of an electrochromic-photothermal film by integrating electrochromic WO with plasmonic Au nanostructures and demonstrate its adjustability during optical transmission and photothermal conversion of visible and NIR lights. The localized surface plasmon resonance (LSPR) of Au nanostructures and the broadband nonradiative plasmon decay are proposed to be tunable using both the electric field and the WO substrate. Further enhanced photothermal conversion is achieved in colored state, which is attributed to coupling of traditional visible-band optical switching with NIR-LSPR extinction. The resulted electrochromic-photothermal film can also effectively reduce the numbers of attacking microorganisms, thus promising for use as a sterile smart window for advanced applications.