Light-Controlled Ionic Transport through Molybdenum Disulfide Membranes

Bioinspired Light-Driven Proton Pump: Engineering Band Alignment of WS2 with PEDOT:PSS and PDINN

Bioinspired two-dimensional (2D) nanofluidic systems for photo-induced ion transport have attracted great attention, as they open a new pathway to enabling light-to-ionic energy conversion. However, there is still a great challenge in achieving a satisfactory performance. It is noticed that organic solar cells (OSCs, light-harvesting device based on photovoltaic effect) commonly require hole/electron transport layer materials (TLMs), PEDOT:PSS (PE) and PDINN (PD), respectively, to promote the energy conversion. Inspired by such a strategy, an artificial proton pump by coupling a nanofluidic system with TLMs is proposed, in which the PE- and PD-functionalized tungsten disulfide (WS2) multilayers construct a heterogeneous membrane, realizing an excellent output power of ≈1.13 nW. The proton transport is fine-regulated due to the TLMs-engineered band structure of WS2. Clearly, the incorporating TLMs of OSCs into 2D nanofluidic systems offers a feasible and promising approach for band edge engineering and promoting the light-to-ionic energy conversion.

Ion transport in nanofluidics under external fields

Nanofluidic channels with tailored ion transport dynamics are usually used as channels for ion transport, to enable high-performance ion regulation behaviors. The rational construction of nanofluidics and the introduction of external fields are of vital significance to the advancement and development of these ion transport properties. Focusing on the recent advances of nanofluidics, in this review, various dimensional nanomaterials and their derived homogeneous/heterogeneous nanofluidics are first briefly introduced. Then we discuss the basic principles and properties of ion transport in nanofluidics. As the major part of this review, we focus on recent progress in ion transport in nanofluidics regulated by external physical fields (electric field, light, heat, pressure, etc.) and chemical fields (pH, concentration gradient, chemical reaction, etc.), and reveal the advantages and ion regulation mechanisms of each type. Moreover, the representative applications of these nanofluidic channels in sensing, ionic devices, energy conversion, and other areas are summarized. Finally, the major challenges that need to be addressed in this research field and the future perspective of nanofluidics development and practical applications are briefly illustrated.

Bioinspired 2D nanofluidic membranes for energy applications

Bioinspired two-dimensional (2D) nanofluidic membranes have been explored for the creation of high-performance ion transport systems that can mimic the delicate transport functions of living organisms. Advanced energy devices made from these membranes show excellent energy storage and conversion capabilities. Further research and development in this area are essential to unlock the full potential of energy devices and facilitate the development of high-performance equipment toward real-world applications and a sustainable future. However, there has been minimal review and summarization of 2D nanofluidic membranes in recent years. Thus, it is necessary to carry out an extensive review to provide a survey library for researchers in related fields. In this review, the classification and the raw materials that are used to construct 2D nanofluidic membranes are first presented. Second, the top-down and bottom-up methods for constructing 2D membranes are introduced. Next, the applications of bioinspired 2D membranes in osmotic energy, hydraulic energy, mechanical energy, photoelectric conversion, lithium batteries, and flow batteries are discussed in detail. Finally, the opportunities and challenges that 2D nanofluidic membranes are likely to face in the future are envisioned. This review aims to provide a broad knowledge base for constructing high-performance bioinspired 2D nanofluidic membranes for advanced energy applications.

2D materials: increscent quantum flatland with immense potential for applications

Quantum flatland i.e., the family of two dimensional (2D) quantum materials has become increscent and has already encompassed elemental atomic sheets (Xenes), 2D transition metal dichalcogenides (TMDCs), 2D metal nitrides/carbides/carbonitrides (MXenes), 2D metal oxides, 2D metal phosphides, 2D metal halides, 2D mixed oxides, etc. and still new members are being explored. Owing to the occurrence of various structural phases of each 2D material and each exhibiting a unique electronic structure; bestows distinct physical and chemical properties. In the early years, world record electronic mobility and fractional quantum Hall effect of graphene attracted attention. Thanks to excellent electronic mobility, and extreme sensitivity of their electronic structures towards the adjacent environment, 2D materials have been employed as various ultrafast precision sensors such as gas/fire/light/strain sensors and in trace-level molecular detectors and disease diagnosis. 2D materials, their doped versions, and their hetero layers and hybrids have been successfully employed in electronic/photonic/optoelectronic/spintronic and straintronic chips. In recent times, quantum behavior such as the existence of a superconducting phase in moiré hetero layers, the feasibility of hyperbolic photonic metamaterials, mechanical metamaterials with negative Poisson ratio, and potential usage in second/third harmonic generation and electromagnetic shields, etc. have raised the expectations further. High surface area, excellent young's moduli, and anchoring/coupling capability bolster hopes for their usage as nanofillers in polymers, glass, and soft metals. Even though lab-scale demonstrations have been showcased, large-scale applications such as solar cells, LEDs, flat panel displays, hybrid energy storage, catalysis (including water splitting and CO₂ reduction), etc. will catch up. While new members of the flatland family will be invented, new methods of large-scale synthesis of defect-free crystals will be explored and novel applications will emerge, it is expected. Achieving a high level of in-plane doping in 2D materials without adding defects is a challenge to work on. Development of understanding of inter-layer coupling and its effects on electron injection/excited state electron transfer at the 2D-2D interfaces will lead to future generation heterolayer devices and sensors.

An Ultraviolet/Visible Light Regulated Protein Transport Gate Constructed by Pillar[6]arene-based Host-Guest System

Protein transport is an interesting and intrinsic life feature that is highly relevant to physiology and disease in living beings. Herein, inspired by nature, based on the supramolecular host-guest interaction, we have introduced the classical azobenzene light switches and L-phenylalanine derived pillar[6]arene (L-Phe-P6) into the artificial nanochannel to construct light-responsive nanochannels that could regulate protein transport effectively under the control of ultraviolet (UV) and visible (Vis) light. The light-controlled distribution of L-Phe-P6 in the channel led to the difference in surface charges in the nanochannel, which eventually brought the difference in protein transport. This research may not only provide a convenient theoretical model for biological research, but also a flexible light-responsive protein transport model, which will play a crucial role in light-controlled release of protein drugs and so on.

Light-Controlled Ionic/Molecular Transport through Solid-State Nanopores and Nanochannels

Biological nanochannels perfectly operate in organisms and exquisitely control mass transmembrane transport for complex life process. Inspired by biological nanochannels, plenty of intelligent artificial solid-state nanopores and nanochannels are constructed based on various materials and methods with the development of nanotechnology. Specially, the light-controlled nanopores/nanochannels have attracted much attention due to the unique advantages in terms of that ion and molecular transport can be regulated remotely, spatially and temporally. According to the structure and function of biological ion channels, light-controlled solid-state nanopores/nanochannels can be divided into light-regulated ion channels with ion gating and ion rectification functions, and light-driven ion pumps with active ion transport property. In this review, we present a systematic overview of light-controlled ion channels and ion pumps according to the photo-responsive components in the system. Then, the related applications of solid-state nanopores/nanochannels for molecular sensing, water purification and energy conversion are discussed. Finally, a brief conclusion and short outlook are offered for future development of the nanopore/nanochannel field.