Two-photon excitation provides a means of activating chemical or physical processes with high spatial resolution in three dimensions and has made possible the development of three-dimensional fluorescence imaging, optical data storage, and lithographic microfabrication. These applications take advantage of the fact that the two-photon absorption probability depends quadratically on intensity, so under tight-focusing conditions, the absorption is confined at the focus to a volume of order λ3 (where λ is the laser wavelength). Any subsequent process, such as fluorescence or a photoinduced chemical reaction, is also localized in this small volume. Although three-dimensional data storage and microfabrication have been illustrated using two-photon-initiated polymerization of resins incorporating conventional ultraviolet-absorbing initiators, such photopolymer systems exhibit low photosensitivity as the initiators have small two-photon absorption cross-sections (δ). Consequently, this approach requires high laser power, and its widespread use remains impractical. Here we report on a class of π;-conjugated compounds that exhibit large δ (as high as 1, 250 × 10−50 cm4 s per photon) and enhanced two-photon sensitivity relative to ultraviolet initiators. Two-photon excitable resins based on these new initiators have been developed and used to demonstrate a scheme for three-dimensional data storage which permits fluorescent and refractive read-out, and the fabrication of three-dimensional micro-optical and micromechanical structures, including photonic-bandgap-type structures.

Two-photon polymerization initiators for three-dimensional optical data storage and microfabrication

The key challenge to developing renewable and clean energy technologies lies in the rational design and synthesis of efficient and earth-abundant catalysts for a wide variety of electrochemical reactions. This review presents materials design strategies for constructing improved electrocatalysts based on MOF precursors/templates, with special emphasis on component manipulation, morphology control, and structure engineering. Guided by these strategies, recently developed MOF-derived materials have exhibited remarkable activity, selectivity, and stability for various energy-conversion processes, manifesting great potential for replacing precious-metal-based catalysts in next-generation energy devices. Existing challenges and opportunities regarding MOF-derived electrocatalysts are also discussed. It is anticipated that by extending current materials design strategies to a wider range of MOF precursors for various energy-related electrocatalytic reactions, significant advances toward achieving highly efficient electrocatalysts can be made.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/aenm.201700518

Design Strategies toward Advanced MOF-Derived Electrocatalysts for Energy-Conversion Reactions

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters. Over the last decade, different nanomaterials have been exploited to design highly efficient biosensors for the detection of analyte biomolecules. The discovery of graphene has spectacularly accelerated research on fabricating low-cost electrode materials because of its unique physical properties, including high specific surface area, high carrier mobility, high electrical conductivity, flexibility, and optical transparency. Graphene and its oxygenated derivatives, including graphene oxide (GO) and reduced graphene oxide (rGO), are becoming an important class of nanomaterials in the field of biosensors. The presence of oxygenated functional groups makes GO nanosheets strongly hydrophilic, facilitating chemical functionalization. Graphene, GO and rGO nanosheets can be easily combined with various types of inorganic nanoparticles, including metals, metal oxides, semiconducting nanoparticles, quantum dots, organic polymers and biomolecules, to create a diverse range of graphene-based nanocomposites with enhanced sensitivity for biosensor applications. This review summarizes the advances in two-dimensional (2D) and three-dimensional (3D) graphene-based nanocomposites as emerging electrochemical and fluorescent biosensing platforms for the detection of a wide range of biomolecules with enhanced sensitivity, selectivity and a low limit of detection. The biofunctionalization and nanocomposite formation processes of graphene-based materials and their unique properties, surface functionalization, enzyme immobilization strategies, covalent immobilization, physical adsorption, biointeractions and direct electron transfer (DET) processes are discussed in connection with the design and fabrication of biosensors. The enzymatic and nonenzymatic reactions on graphene-based nanocomposite surfaces for glucose- and cholesterol-related electrochemical biosensors are analyzed. This review covers a very broad range of graphene-based electrochemical and fluorescent biosensors for the detection of glucose, cholesterol, hydrogen peroxide (H2O2), nucleic acids (DNA/RNA), genes, enzymes, cofactors nicotinamide adenine dinucleotide (NADH) and adenosine triphosphate (ATP), dopamine (DA), ascorbic acid (AA), uric acid (UA), cancer biomarkers, pathogenic microorganisms, food toxins, toxic heavy metal ions, mycotoxins, and pesticides. The sensitivity and selectivity of graphene-based electrochemical and fluorescent biosensors are also examined with respect to interfering analytes present in biological systems. Finally, the future outlook for the development of graphene based biosensing technology is outlined.

/pdf/a-review-on-graphene-based-nanocomposites-for-3tflsf8hnn.pdf

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

As emerging crystalline porous organic-inorganic hybrid materials, metal-organic frameworks (MOFs) have been widely used as sacrificial precursors for the synthesis of carbon materials, metal/metal compounds, and their composites with tunable and controllable nanostructures and chemical compositions for electrochemical energy applications. Herein, recent progress of MOF-derived nanomaterials for various electrochemical energy storage and conversion applications including Li-ion batteries, Li-S batteries, Na-ion batteries, supercapacitors, water splitting, and oxygen reduction reaction is reviewed. Structural and compositional design of MOF-derived nanomaterials is systematically summarized, which may hopefully offer inspirations and guidances for future development of MOF-derived nanomaterials for more efficient and more durable electrochemical energy applications.

Metal-organic framework-derived materials for electrochemical energy applications

The energy consumption of hydrogen production from electrolytic water splitting originates from the oxygen evolution reaction (OER). Development of efficient and cost-effective OER electrocatalysts has become a high-priority research task. In this regard, layered double hydroxides (LDHs) as one of the promising OER electrocatalysts have been intensely researched due to their unique 2D layered structure and excellent physicochemical properties. Herein, this review aims to summarize recent strategies to design LDHs, including nanostructuring, hybrid LDHs with conductive materials, partial substitution of cations, interlayer anion replacement, vacancy creation, and combination of computational methods and operando techniques. Specifically, a thorough literature overview in the developments of LDHs to improve OER performance is appraised in detail, based on the compositional difference of transition metal components. Challenges and future directions in designing LDHs as OER electrocatalysts are discussed. The provided discussion will be favorable to explore and develop better catalysts and device units for practical applications and will offer a basic understanding of the OER process along with key issues to evaluate the performance.

Recent advances in layered double hydroxide electrocatalysts for the oxygen evolution reaction

Temperature-sensitive and solvent-resistance hydrogel sensor for ambulatory signal acquisition in “moist/hot environment”

Ionogels with self-healing properties have become more and more desirable because they can improve the reliability, safety, and fatigue-resistant performance of flexible devices. However, the self-healing property of ionogels is usually susceptible to water molecules, and the application of ionogel sensors is limited to the atmospheric environment. Inspired by gelatinous jellyfish, herein, an underwater self-healing ionogel was prepared via one-step photoinitiated polymerization of acrylic acid 2,2,2-trifluoroethyl ester and N-isopropylacrylamide (NIPAm) in a hydrophobic ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIm][TFSI]). The dynamic physical interactions (hydrogen bonding and ion-dipole interactions) endowed the ionogel with remarkable transparency, underwater self-healing (up to 96%), toughness (3.93 MJ m-3), and underwater adhesion. And the cross-linking ionogel could be green recycled by ethanol for further application. Especially, the ionogel-based sensor presented excellent strain and pressure sensing sensitivity, rapid responsiveness (140 ms), and ultrastability. The ionogel could be further assembled into an optical camouflage sensor to detect and distinguish different human motions in real time with high sensitivity, stability, and repeatability, as well as for underwater electrocardiography monitoring wirelessly. This ionogel provides a promising strategy for the development of underwater self-healing sensors.

Underwater Self-Healing and Recyclable Ionogel Sensor for Physiological Signal Monitoring.

The invention relates to a high-strength polymer membrane, a preparation method and novel application of a diluting agent A thermally induced phase separation method is adopted; meanwhile, the diluting agent with relatively low toxicity and a carbon-carbon double bond is adopted, and is used as a plasticizer in a processing and molding process of a polymer; the plasticizer and the polymer are subjected to melting grafting reaction; less diluting agent is grafted into a polymer chain, so that the prepared polymer porous membrane has very high strength and flexibility Therefore, a prepared flat plate membrane or hollow fiber membrane has relatively high mechanical properties; the tensile strength can reach 10MPa, and the pure water flux is 1000l/(m *h) or more

High-strength polymer membrane, preparation method and application of diluting agent

The development of fast and economical hydrogel manufacturing methods is crucial for expanding the application of hydrogels. However, the commonly used rapid initiation system is not conducive to the performance of hydrogels. Therefore, the research focuses on how to improve the preparation speed of hydrogels and avoid affecting the properties of hydrogels. Herein, a redox initiation system with nanoparticle-stabilized persistent free radicals was introduced to rapidly synthesize high-performance hydrogels at room temperature. A redox initiator composed of vitamin C and ammonium persulfate rapidly provides hydroxyl radicals at room temperature. Simultaneously, three-dimensional nanoparticles can stabilize free radicals and prolong their lifetime, thereby increasing the free radical concentration and accelerating the polymerization rate. And casein enabled the hydrogel to achieve impressive mechanical properties, adhesion, and electrical conductivity. This method greatly facilitates the rapid and economical synthesis of high-performance hydrogels and presents broad application prospects in the field of flexible electronics.

/pdf/in-situ-rapid-synthesis-of-hydrogels-based-on-a-redox-2bowgx9j.pdf

Qian Wang

Papers

Temperature-sensitive and solvent-resistance hydrogel sensor for ambulatory signal acquisition in “moist/hot environment”

Underwater Self-Healing and Recyclable Ionogel Sensor for Physiological Signal Monitoring.

High-strength polymer membrane, preparation method and application of diluting agent

In situ rapid synthesis of hydrogels based on a redox initiator and persistent free radicals

Photocatalysis in energy application: What’s next?