Anodic TiO2 nanotube arrays prepared by electrochemical anodization were used to fabricate ultraviolet (UV) photodetectors. The devices annealed at 450 °C exhibit the highest UV-sensitive photoconductance due to the pure anatase phase of the TiO2. The large surface area and one-dimensional nanostructure of the TiO2 nanotubes lead to great photosensitivity (more than 4 orders of magnitude) and fast response with rise time and decay time of 0.5 and 0.7 s, respectively. High responsivity of 13 A/W is found under 1.06 mW/cm2 UV (λ = 312 nm) illumination at 2.5 V bias, which is much higher than those of commercial UV photodetectors. The high responsivity mainly comes from the internal gain induced by the desorption of oxygen from the nanotube surfaces and the reduction of the Schottky barrier at TiO2/Ag contact under UV illumination. The devices are promising for large-area UV photodetctor applications.

Abstract2D materials are gaining great attention owing to their superior electrical, optical, and mechanical characteristics. In recent decades, 2D materials have demonstrated significant potential for the identification of disease‐related biomarkers based on semiconductor gas sensors. Herein, the recent progress of semiconductor gas sensors fabricated by 2D materials covering graphene, black phosphorus, transition metal dichalcogenides, MXenes, metal‐organic frameworks, metal oxide nanosheets, etc. is clearly described. First, the basic attributes of 2D materials are described, and their gas‐sensing mechanisms are also summarized. Second, the ability of 2D material‐based sensors in the detection of disease‐related gas molecules is also highlighted. Finally, some effective methods for enhancing the gas‐sensing performance of 2D materials are discussed, and the opportunities and challenges accompanying are also presented. This work could provide new avenues for material synthesis, sensor development, medical diagnosis, and the related fields.

With the rapid development of portable electronics, solid-state flexible supercapacitors (SCs) are considered as one of the promising energy devices in powering electronics because of their intrinsic advantages. Polypyrrole (PPy) is an ideal electrode material in constructing flexible SCs owing to its high electrochemical activity and inherent flexibility, although its relatively low capacitance and poor cycling stability are still worthy of improvement. Herein, through the innovative introduction of black phosphorus (BP) nanosheets, we developed a laminated PPy/BP self-standing film with enhanced capacitance and cycling stability via a facile one-step electrochemical deposition method. The film exhibits a high capacitance of 497.5 F g (551.7 F cm) and outstanding cycling stability of 10 000 charging/discharging cycles, thanks to BP nanosheets inducing laminated assembly which hinder dense and disordered stacking of PPy during electrodeposition, consequently providing a precise pathway for ion diffusion and electron transport together with alleviation of the structural deterioration during charge/discharge. The flexible SC fabricated by laminated films delivers a high capacitance of 452.8 F g (7.7 F cm) besides its remarkable mechanical flexibility and cycling stability. Our facile strategy paves the way to improve the electrochemical performance of PPy-based SC that could serve as promising flexible energy device for portable electronics.

We report multiscale structured fibers and patterned films based on a semiconducting polymer, poly(3hexylthiophene) (P3HT), as photoconductive biointerfaces to promote neuronal stimulation upon light irradiation. The micro/nanoscale structures of P3HT used for neuronal interfacing and stimulation include nanofibers with an average diameter of 100 nm, microfibers with an average diameter of about 1 μm, and lithographically patterned stripes with width of 3, 25, and 50 μm, respectively. The photoconductive effect of P3HT upon light irradiation provides electrical stimulation for neuronal differentiation and directed growth. Our results demonstrate that neurons on P3HT nanofibers showed a significantly higher total number of branches, while neurons grown on P3HT microfibers had longer and thinner neurites. Such a combination strategy of topographical and photoconductive stimulation can be applied to further enhance neuronal differentiation and directed growth. These photoconductive polymeric micro/nanostructures demonstrated their great potential for neural engineering and development of novel neural regenerative devices.

A novel method is described for the preparation of sterile submicron unilamellar liposomes. The method is based on the lyophilization of double emulsions containing disaccharides as lyoprotectants in both the inner and outer aqueous phase. Using various phospholipids or mixtures of lipids as emulsifiers, the double emulsions can be prepared by a two-step emulsification, including hydrophilic agents in the inner aqueous phase or lipophilic agents in the oil phase. Then, the double emulsions are lyophilized after sterilization by passing them through a 0.22-microm pore filter. Rehydration of the lyophilized products results in liposomes with a relatively high encapsulation efficiency (for calcein, 87%; 5-fluorouracil, 19%; flurbiprofen, 93%) and a size below 200 nm measured by the dynamic light scattering technique (DLS) and the atomic force microscopy (AFM). The liposomes were found to be unilamellar from freeze-fracture electron micrographs and X-ray diffraction patterns. In addition, the liposomes can be reconstituted just before use by rehydration of the lyophilized products which are relatively stable. Thus, this reproducible and simple technique can be used to prepare sterilized, submicron unilamellar liposomes with a relatively high encapsulation efficiency, and excellent stability during long-term storage.

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As a promising chemiresistor for gas sensing, the single-walled carbon nanotube (SWCNT) network has not yet been fully utilized for humidity detection. In this work, it is found that as humidity increases from 10% to 85%, the resistance of as-grown SWCNT networks first decreases and then increases. This non-monotonic resistive response to humidity limits their sensing capabilities. The competition between SWCNT resistance and inter-tube junction resistance changes is then found to be responsible for the non-monotonic resistive humidity responses. Moreover, creating sp(3) scattering centers on the SWCNT sidewall by monovalent functionalization of four-bromobenzene diazonium tetrafluoroborate is shown to be capable of eliminating the influence from the inter-tube junctions, resulting in a continuous resistance drop as humidity increases from 10% to 85%. Our results revealed the competing resistive humidity sensing process in as-grown SWCNT networks, which could also be helpful in designing and optimizing as-grown SWCNT networks for humidity sensors and other gas sensors.