Jue Hou

Bio-Inspired Photonic-Crystal Microchip for Fluorescent Ultratrace Detection†

Ultratrace detection attracts great interest because it is still a challenge to the early diagnosis and drug testing. Enriching the targets from highly diluted solutions to the sensitive area is a promising method. Inspired by the fog-collecting structure on Stenocara beetles back, a photonic-crystal (PC) microchip with hydrophilic-hydrophobic micropattern was fabricated by inkjet printing. This device was used to realize high-sensitive ultratrace detection of fluorescence analytes and fluorophore-based assays. Coupled with the fluorescence enhancement effect of a PC, detection down to 10(-16) mol L(-1) was achieved. This design can be combined with biophotonic devices for the detection of drugs, diseases, and pollutions of the ecosystem.

Hydrophilic-Hydrophobic Patterned Molecularly Imprinted Photonic Crystal Sensors for High-Sensitive Colorimetric Detection of Tetracycline

A hydrophilic-hydrophobic patterned molecularly imprinted (MIP) photonic crystal (PC) sensor is fabricated for highly sensitive tetracycline detection. The relationship between the tetracycline concentration, its corresponding color of the sensor, and the diameter of MIP-PC dot is found using a fan-shaped color card. This work provides a new strategy to design the sensors with tunable detection ranges for practical applications.

Bioinspired Smart Gate-Location-Controllable Single Nanochannels: Experiment and Theoretical Simulation.

pH-activated gates intelligently govern the ion transport behaviors of a wide range of bioinspired ion channels, but the mechanisms between the gate locations and the functionalities of the ion channels remain poorly understood. Here, we construct an artificial gate-location-tunable single-nanochannel system to systematically investigate the impact of the gate location on the ion transport property of the biomimetic ion channel. The gate-location-controllable single nanochannels are prepared by asymmetrically grafting pH-responsive polymer gates on one side of single nanochannels with gradual shape transformation. Experimental ion current measurements show that the gating abilities and rectification effects of the pH-gated nanochannels can be gradually altered by precisely locating the artificial pH gates on the different sites of the channels. The experimental gate-location-dependent gating and rectification of ion current in the bioinspired ion channel system is further well confirmed by theoretical simulation. This work, as an example, provides a new avenue to optimize the smart ion transport features of diverse artificial nanogate devices via precisely locating the gates on the appropriate sites of the artificial nanochannels.

Patterned Colloidal Photonic Crystals

Colloidal photonic crystals (PCs) have been well developed because they are easy to prepare, cost-effective, and versatile with regards to modification and functionalization. Patterned colloidal PCs contribute a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate-induced assembly, inkjet printing, and selective immobilization and modification, is presented. The advantages of patterned PC devices are also discussed in detail, for example, improved detection sensitivity and response speed of the sensors, control over the flow direction and wicking rate of microfluidic channels, recognition of cross-reactive molecules through an array-patterned microchip, fabrication of display devices with tunable patterns, well-arranged RGB units, and wide viewing-angles, and the ability to construct anti-counterfeiting devices with different security strategies. Finally, the perspective of future developments and challenges is presented.

Four-Dimensional Screening Anti-Counterfeiting Pattern by Inkjet Printed Photonic Crystals

A four-dimensional screening anti-counterfeiting QR code composed of differently shaped photonic crystal (PC) dots has been fabricated that could display four images depending on different lighting conditions. By controlling the rheology of poly(dimethylsiloxane) (PDMS), three kinds of PC dots could be sequentially integrated into one pattern using the layer-by-layer printing strategy. The information can be encoded and stored in shapes and read out by the difference in optical properties.

Efficient Luminescence of Long Persistent Phosphor Combined with Photonic Crystal

In this paper, the luminescence properties of the long persistent phosphor (LPP) were apparently improved by combining with photonic crystal (PC). An optimized PC can double the afterglow intensity and prolong 1.7 times of the afterglow time of SrAl2O4: Eu, a commercially available LPP, without any dopants. These results were ascribed to the stopband effect of the PC. The PC combined LPP structure was beneficial for the applications of LPP in emergency indication which called for brighter afterglow intensity and longer afterglow time.

Oscillatory Reaction Induced Periodic C-Quadruplex DNA Gating of Artificial Ion Channels

Many biological ion channels controlled by biochemical reactions have autonomous and periodic gating functions, which play important roles in continuous mass transport and signal transmission in living systems. Inspired by these functional biological ion channel systems, here we report an artificial self-oscillating nanochannel system that can autonomously and periodically control its gating process under constant conditions. The system is constructed by integrating a chemical oscillator, consisting of BrO3-, Fe(CN)64-, H+, and SO32-, into a synthetic proton-sensitive nanochannel modified with C-quadruplex (C4) DNA motors. The chemical oscillator, containing H+-producing and H+-consuming reactions, can cyclically drive conformational changes of the C4-DNA motors on the channel wall between random coil and folded i-motif structures, thus leading to autonomous gating of the nanochannel between open and closed states. The autonomous gating processes are confirmed by periodic high-low ionic current oscillations of the channel monitored under constant reaction conditions. The utilization of a chemical oscillator integrated with DNA molecules represents a method to directly convert chemical energy of oscillating reactions to kinetic energy of conformational changes of the artificial nanochannels and even to achieve diverse autonomous gating functions in artificial nanofluidic devices.

Healable green hydrogen bonded networks for circuit repair, wearable sensor and flexible electronic devices

Healable materials have wide applications, particularly in flexible electronics. Developing healable materials with green preparations, manipulations and post-processes, and moderate healing conditions is still a challenge. Herein, inspired by the natural healing phenomena based on hydrogen bonding interaction, a green hydrogen bonded network (GHBN), a hydrogel consisting of eco-friendly materials and connected by hydrogen bonding interaction, that is healable, reshapable, injectable, conductive, renewable, cost-effective and eco-friendly is fabricated using amylopectin/water as the skeleton and free-moving ions as the current carrier. This ternary GHBN can heal rapidly in both mechanical and electrical fields at room temperature. The healing process lasts just 2–3 s without any specific environment, and the healing efficiency reaches 98%. The mechanisms of hydrogen bonded network formation and the healing process are well studied by computational simulations. The GHBN exhibits excellent performance in circuit repair, wearable sensors and flexible electronic devices. This study provides a new strategy to develop electrode materials using natural hydrogen bonded molecules as skeletons that may be applied as flexible electronics.

Single Nanochannel-Aptamer-Based Biosensor for Ultrasensitive and Selective Cocaine Detection

Ultrasensitive and selective detection of molecules at nano or sub-nanomolar level is very important for many areas such as early diagnosis and drug testing. Herein, we report a high-sensitive cocaine sensor based on a single nanochannel coupled with DNA aptamers. The single nanochannel-aptamer-based biosensor can recognize cocaine molecules with an excellent sensitivity and good selectivity. A linear relationship between target cocaine concentration and output ionic current is obtained in a wide concentration range of cocaine from 1 nM to 10 μM. The cocaine sensor also shows a detection limit down to 1 nM. This study provides a new avenue to develop new nanochannel-aptamer-based biosensors for rapid and ultratrace detection of a variety of illicit drugs.

Carbon Nanotube Networks as Nanoscaffolds for Fabricating Ultrathin Carbon Molecular Sieve Membranes

Carbon molecular sieve (CMS) membranes have shown great potential for gas separation owing to their low cost, good chemical stability, and high selectivity. However, most of the conventional CMS membranes exhibit low gas permeance due to their thick active layer, which limits their practical applications. Herein, we report a new strategy for fabricating CMS membranes with a 100 nm-thick ultrathin active layer using poly(furfuryl alcohol) (PFA) as a carbon precursor and carbon nanotubes (CNTs) as nanoscaffolds. CNT networks are deposited on a porous substrate as nanoscaffolds, which guide PFA solution to effectively spread over the substrate and form a continuous layer, minimizing the penetration of PFA into the pores of the substrate. After pyrolysis process, the CMS membranes with 100-1000 nm-thick active layer can be obtained by adjusting the CNT loading. The 322 nm-thick CMS membrane exhibits the best trade-off between the gas permeance and selectivity, a H2 permeance of 4.55 × 10-8 mol m-2 s-1 Pa-1, an O2 permeance of 2.1 × 10-9 mol m-2 s-1 Pa-1, and an O2/N2 ideal selectivity of 10.5, which indicates the high quality of the membrane produced by this method. This work provides a simple, efficient strategy for fabricating ultrathin CMS membranes with high selectivity and improved gas flux.