Titanium Oxide/Silicon Moth-Eye Structures with Antireflection, p-n Heterojunctions, and Superhydrophilicity

Paper-Supported Photoelectrochemical Biosensor for Dual-Mode miRNA-106a Assay: Integration of Luminescence-Confined Upconversion-Actuated Fluorescent Resonance Energy Transfer and CRISPR/Cas13a-Powered Cascade DNA Circuits

Near-infrared (NIR)-responsive bioassays based on upconversion nanoparticle (UCNP) incorporating high-performance semiconductors have been developed by researchers, but most lack satisfactory ultrasensitivity for exceedingly trace amounts of target. Herein, for the first time, the CRISPR/Cas13a system is combined with cascade DNA circuits, fluorescent resonance energy transfer (FRET) effect, and luminescence-confined UCNPs-bonded CuInS2/ZnO p-n heterostructures-functionalized paper-working electrode to construct dual-signal-on paper-supported NIR-irradiated photoelectrochemical (PEC) (NIR-PEC) and upconversion luminescence (UCL) bioassay for high-sensitive quantification of miRNA-106a (miR-106a). By constructing an ideal FAM-labeled aminating molecular beacon (FAM-H2) model, a relatively good FRET ratio between the UCNP and FAM (≈85.3%) can be achieved. In the existence of miR-106a, the hairpin-structure FAM-H2 was unwound, bringing about the distance increase of UCNP and FAM and the restraint of FRET. Accordingly, both the NIR-PEC signal and the UCL intensity gradually recovered distinctly. Unlike conventional single-mode PEC sensors, with NIR excitation, the designed dual-mode sensing system could implement minimized misdiagnose assay and quantitative miR-106a determination with low detection limits, that is, 76.54 and 51.36 aM for NIR-PEC and UCL detection, respectively. This work not only broadens the horizon of application of the CRISPR/Cas13a strategy toward biosensing but also constructs a new structure of the UCNP-semiconductor in the exploration of efficient NIR-responsive tools and inspires the construction of a no-misdiagnosed and novel biosensor for dual-mode liquid biopsy.

A Simple Polypyrrole/Polyvinylidene Fluoride Membrane with Hydrophobic and Self-Floating Ability for Solar Water Evaporation

The traditional hydrophobic solarevaporator is generally obtained through the modification of alkyl or fluoroalkyl on the photothermal membrane. However, the modified groups can easily be oxidized in the long-term use process, resulting in the poor salt resistance and stability of photothermal membrane. In order to solve this problem, a simple polypyrrole/polyvinylidene fluoride membrane, consisting of an intrinsic hydrophobic support (polyvinylidene fluoride) and a photothermal material (polypyrrole), was fabricated by ultrasonically mixing and immersed precipitation. This photothermal membrane showed good self-floating ability in the process of water evaporation. In order to further improve the photothermal conversion efficiency, a micropyramid structure with antireflective ability was formed on the surface of membrane by template method. The micropyramids can enhance the absorption efficiency of incident light. The water evaporation rate reached 1.42 kg m⁻² h⁻¹ under 1 sun irradiation, and the photothermal conversion efficiency was 88.7%. The hydrophobic polyvinylidene fluoride ensures that NaCl cannot enter into membrane during the evaporation process of the brine, thus realizing the stability and salt resistance of polypyrrole/polyvinylidene fluoride in 3.5%wt and 10%wt NaCl solution.

Micro-Nano Machining TiO2 Patterns without Residual Layer by Unconventional Imprinting

Usually, the residual layer remains after patterning TiO2 sol. The existence of the TiO2 residual layer in the non-pattern region affects its application in microelectronic devices. Here, a simple method, based on room-temperature imprinting, to fabricate a residual-free TiO2 pattern is proposed. The thermoplastic polymer with Ti4+ salt was fast patterned at room temperature by imprinting, based on the different interfacial force. Then, the patterned thermoplastic polymer with Ti4+ salt was induced into the TiO2 lines without residual layer under the hydrothermal condition. This method provides a new idea to pattern metal oxide without residual layer, which is potentially applied to the gas sensor, the optical detector and the light emitting diode.

A novel photothermal, self-healing and anti-reflection water evaporation membrane

For the solar water evaporation system, there are no reports on the self-healing support, which is crucial for the sustainable use of solar evaporation membrane. In this work, a self-healing hydrogel is prepared via free radical copolymerization with covalent cross-linking and coordination cross-linking and is used as a photothermal water evaporation support. The photothermal material is then introduced into the hydrogel by physically doping acetylene carbon black. At the same time, inverted micro-pyramids are fabricated on the surface of the hydrogel by soft imprint to increase the utilization efficiency of incident light. The water evaporation rate of the composite membrane can reach 1.58 kg m-2 h-1, and the breaking elongation is 1580%. It can self-heal after it is completely broken, and can still be stretched 3 times its original length. The design of this self-healing photothermal membrane will provide a new idea for its application in a harsh outdoor environment.

Light-Trapping SERS Substrate with Regular Bioinspired Arrays for Detecting Trace Dyes

Recently, few studies have focused on the light-trapping surface-enhanced Raman scattering (SERS) substrate combined with Si micropyramids and Ag (or Au). However, the Si micropyramids possess no ordered period, which not only affects the repeatability of the SERS signal but also affects the theoretical exploration. Here, the ordered micropyramids with strong light-trapping capability were fabricated by utilizing unconventional nanosphere lithography and anisotropy wet etching technique. Then, the Ag nanobowls were assembled on the ordered micropyramids to form the SERS substrate with bioinspired compound-eyes structure by utilizing the liquid-solid interface self-assembly and transfer technique. Especially, the evidence for the contribution of antireflective Si micropyramids to Raman enhancement was first presented. For this bioinspired SERS substrate, the lowest concentration of R6G that can be detected is 10^-13 M with the level of a single molecule, and the relative standard deviation (RSD) is 3.68%. Meanwhile, the quantitative analysis and qualitative analysis can be realized. Especially, simultaneous trace detection of four common dyes (R6G, CV, MG, and MB) in food can be realized, suggesting that this SERS substrate will have a good application prospect in the field of optical sensors.

Bioinspired Microstructured Materials for Optical and Thermal Regulation

Precise optical and thermal regulatory systems are found in nature, specifically in the microstructures on organisms' surfaces. In fact, the interaction between light and matter through these microstructures is of great significance to the evolution and survival of organisms. Furthermore, the optical regulation by these biological microstructures is engineered owing to natural selection. Herein, the role that microstructures play in enhancing optical performance or creating new optical properties in nature is summarized, with a focus on the regulation mechanisms of the solar and infrared spectra emanating from the microstructures and their role in the field of thermal radiation. The causes of the unique optical phenomena are discussed, focusing on prevailing characteristics such as high absorption, high transmission, adjustable reflection, adjustable absorption, and dynamic infrared radiative design. On this basis, the comprehensive control performance of light and heat integrated by this bioinspired microstructure is introduced in detail and a solution strategy for the development of low-energy, environmentally friendly, intelligent thermal control instruments is discussed. In order to develop such an instrument, a microstructural design foundation is provided.

An electrochromic supercapacitor based on an MOF derived hierarchical-porous NiO film

Nickel oxide (NiO) is a promising candidate for future electrochromic supercapacitors due to its pronounced electrical properties and low cost. Unfortunately, the weak interaction between NiO films and conductive substrates results in poor cycling stability. In addition, the long color-switching time and low capacitance by the small lattice spacing in dense NiO impede its practical applications seriously. Herein, a hierarchical porous NiO film/ITO glass bifunctional electrode has been prepared via the solvothermal and subsequent calcination process of growing MOF-74 in situ on ITO, which shows outstanding cycle reversibility, excellent capacitance, high coloration efficiency and short color-switching time. Because of the strong binding force between the NiO film and substrate, and large surface areas with a hierarchical porous structure which are beneficial to the ion transport, the NiO film demonstrates perfect capacitive and electrochromic properties. As a bifunctional electrode, the NiO film shows a specific capacitance of 2.08 F cm-2 at 1 mA cm-2, large optical modulation of 41.08% and about 86% of optical modulation retention after 10 000 cycles. Furthermore, we assembled a bifunctional device whose energy condition can be roughly estimated according to the color state of the device. This finding can provide us with a new application of MOFs in the dual device of electrochromic supercapacitors.

Design and Fabrication of Moth-Eye Subwavelength Structure with a Waist on Silicon for Broadband and Wide-Angle Anti-Reflection Property

Reflection loss on the optical component surface is detrimental to performance. Several researchers have discovered that the eyes of moths are covered with micro- and nanostructured films that reduce broadband and wide-angle light reflection. This research proposes a new type of moth-eye subwavelength structure with a waist, which is equivalent to a gradient refractive index film layer with high–low–high hyperbolic-type fill factor distribution. The diffraction order characteristics of a moth-eye subwavelength structure are first analyzed using a rigorous coupled wave analysis. The moth-eye structural parameters are optimized within the spectral range of 2–5 μm using the finite-difference time-domain method. The experimental fabrication of the moth-eye structure with a waist array upon a silicon substrate is demonstrated by using three-beam laser interferometric lithography and an inductively coupled plasma process. The experimental and simulation results show good agreement. The experimental results show that the reflectivity of the moth-eye structure with a waist is less than 1.3% when the incidence angle is less than 30°, and less than 4% when the incidence angle is less than 60°. This research can guide the development of AR broadband optical components and wide-angle applications.

Preparation of Nano-TiO₂-Coated SiO₂ Microsphere Composite Material and Evaluation of Its Self-Cleaning Property

In order to improve the dispersion of nano-TiO₂ particles and enhance its self-cleaning properties, including photocatalytic degradation of pollutants and surface hydrophilicity, we prepared nano-TiO₂-coated SiO₂ microsphere composite self-cleaning materials (SiO₂–TiO₂) by co-grinding SiO₂ microspheres and TiO₂ soliquid and calcining the ground product. The structure, morphology, and self-cleaning properties of the SiO₂–TiO₂ were characterized. The characterization results showed that the degradation efficiency of methyl orange by SiO₂–TiO₂ was 97%, which was significantly higher than that obtained by pure nano-TiO₂. The minimum water contact angle of SiO₂–TiO₂ was 8°, indicating strong hydrophilicity and the good self-cleaning effect. The as-prepared SiO₂–TiO₂ was characterized by the nano-TiO₂ particles uniformly coated on the SiO₂ microspheres and distributed in the gap among the microspheres. The nano-TiO₂ particles were in an anatase phase with the particle size of 15–20 nm. The nano-TiO₂ particles were combined with SiO₂ microspheres via the dehydroxylation of hydroxyl groups on their surfaces.

Photoactive PANI/TiO2/Si composite coatings with 3D bio-inspired structures

We showed that 3D compound-eye coatings with excellent photo-activity could be obtained by anisotropic wet etching, hydrothermal synthesis and chemical oxidation.