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Much of the dramatic growth in research on topological materials has focused on topologically protected surface states. While the domain walls of topological materials such as Weyl semimetals with broken inversion or time-reversal symmetry can provide a hunting ground for exploring topological interfacial states, such investigations have received little attention to date. Here, utilizing in-situ cryogenic transmission electron microscopy combined with first-principles calculations, we discover intriguing domain-wall structures in MoTe2, both between polar variants of the low-temperature(T) Weyl phase, and between this and the high-T higher-order topological phase. We demonstrate how polar domain walls can be manipulated with electron beams and show that phase domain walls tend to form superlattice-like structures along the c axis. Scanning tunneling microscopy indicates a possible signature of a conducting hinge state at phase domain walls. Our results open avenues for investigating topological interfacial states and unveiling multifunctional aspects of domain walls in topological materials.

As a kind of highly effective, low-cost, and stable photocatalysts, TiO 2 has received substantial public and scientific attention. However, it can only be activated under ultraviolet light irradiation due to its wide bandgap, high recombination, and weak separation efficiency of carriers. Doping is an effective method to extend the light absorption to the visible light region. In this chapter, we will address the importance of doping, different doping modes, preparation method, and photocatalytic mechanism in TiO 2 photocatalysts. Thereafter, we will concentrate on Ti 3+ self-doping, nonmetal doping, metal doping, and codoping. Examples of progress can be given for each one of these four doping modes. The influencing factors of preparation method and doping modes on photocatalytic performance (spectrum response, carrier transport, interfacial electron transfer reaction, surface active sites, etc.) are summed up. The main objective is to study the photocatalytic processes, to elucidate the mechanistic models for a better understanding the photocatalytic reactions, and to find a method of enhancing photocatalytic activities.

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We construct colloidal "sticky" rods from the semi-flexible filamentous fd virus and temperature-sensitive polymers poly(N-isopropylacrylamide) (PNIPAM). The phase diagram of fd-PNIPAM system becomes independent of ionic strength at high salt concentration and low temperature, i.e. the rods are sterically stabilized by the polymer. However, the network of sticky rods undergoes a sol-gel transition as the temperature is raised. The viscoelastic moduli of fd and fd-PNIPAM suspensions are compared as a function of temperature, and the effect of ionic strength on the gelling behavior of fd-PNIPAM solution is measured. For all fluidlike and solidlike samples, the frequency-dependant linear viscoelastic moduli can be scaled onto universal master curves.