Graphene on {116} faceted monocrystalline anatase nanosheet array for ultraviolet detection

Application of Nanostructured TiO2 in UV Photodetectors: A Review

As a wide-bandgap semiconductor material, titanium dioxide (TiO₂ ), which possesses three crystal polymorphs (i.e., rutile, anatase, and brookite), has gained tremendous attention as a cutting-edge material for application in the environment and energy fields. Based on the strong attractiveness from its advantages such as high stability, excellent photoelectric properties, and low-cost fabrication, the construction of high-performance photodetectors (PDs) based on TiO₂ nanostructures is being extensively developed. An elaborate microtopography and device configuration is the most widely used strategy to achieve efficient TiO₂ -based PDs with high photoelectric performances; however, a deep understanding of all the key parameters that influence the behavior of photon-generated carriers, is also highly required to achieve improved photoelectric performances, as well as their ultimate functional applications. Herein, an in-depth illustration of the electrical and optical properties of TiO₂ nanostructures in addition to the advances in the technological issues such as preparation, microdefects, p-type doping, bandgap engineering, heterojunctions, and functional applications are presented. Finally, a future outlook for TiO₂ -based PDs, particularly that of further functional applications is provided. This work will systematically illustrate the fundamentals of TiO₂ and shed light on the preparation of more efficient TiO₂ nanostructures and heterojunctions for future photoelectric applications.

Trap-Assisted Charge Storage in Titania Nanocrystals toward Optoelectronic Nonvolatile Memory

Transistor-based memories are of particular significance in the pursuit of next-generation nonvolatile memories. The charge storage medium in a transistor-based memory is pivotal to the device performance. In this report, nitrogen doping titania nanocrystals (N-TiO₂ NCs) synthesized through a low-temperature nonhydrolytic method are used as the charge storage medium in a graphene transistor-based memory. The decoration of the N-TiO₂ NCs enables the device to perform as an ultraviolet (UV) light-programmable nonvolatile optoelectronic memory. Multilevel nonvolatile information recording can be realized through accurate control of the incident light dose, which is ascribed to the vast and firm hole trapping abilities of the N-TiO₂ NCs induced by the N dopant. Accordingly, a positive gate voltage can be used to erase the programmed state by promoting the recombination of stored holes in N-TiO₂ NCs. This study manifests the importance of trap engineering for information storage and provides an alternative path toward nonvolatile optoelectronic memory.

The green exfoliation of graphite waste and its suitability for biosensor applications

This work is concerned with the bio-exfoliation of graphite using a soil bacterium.

High sensitivity ultraviolet detection based on three-dimensional graphene field effect transistors decorated with TiO2 NPs

A three-dimensional (3D) ultraviolet (UV) photodetector was fabricated by decorating a tubular graphene field-effect transistor (GFET) with titanium dioxide (TiO2) nanoparticles (NPs). The unique tubular architecture not only provides a natural 3D optical resonant microcavity to enhance the optical field inside it, but also increases the light-matter interaction area. Strong UV absorption in the TiO2 NPs creates a number of electron-hole pairs, where the electrons are transferred to graphene, while the holes are trapped within the TiO2 NPs, leading to a strong photogating effect on the graphene channel conductance. The photoresponsivity of our 3D GFET photodetector decorated with TiO2 NPs was demonstrated up to 475.5 A W-1 at 325 nm, which is about 2 orders of magnitude higher than that of a 3D GFET photodetector without the TiO2 NP decoration (1 A W-1), and over 3 orders of magnitude higher than that of a recently reported UV photodetector based on the graphene/vertical Ga2O3 nanowire array heterojunction (0.185 A W-1). Moreover, the photoresponsivity and photoresponse speed of the device can be easily tuned by applying a small gate bias (≤3 V) and/or changing the source-drain bias. These results indicate that the photoresponsivities of graphene-based photodetectors can be significantly improved by exploiting 3D graphene structures and integrating graphene with semiconducting light harvesters simultaneously.