Facile Fabrication and Integration of Patterned Nanostructured TiO2 for Microsystems Applications

A simple technique to fabricate integrated crack‐free and crystalline nanostructured titania (ns‐titania) in microsystems devices is presented. In this technique, crack elimination is achieved by oxidizing Ti films, pre‐patterned below a threshold dimension, in aqueous hydrogen peroxide solution. Amorphous ns‐titania with walls of pores having thicknesses and pore diameters ranging from 25 nm–50 nm and 50 nm–200 nm, respectively, is formed after oxidation and transformed to anatase after thermal annealing. We demonstrate the functionality of ns‐titania formed and compatibility of this technique with microsystems device manufacturing practices by fabricating a prototype device for gas sensing using integrated ns‐titania features as sensing elements.     

纳米结构材料在太阳电池中的应用

各种纳米结构材料具有许多优异的光伏性质。例如量子阱具有良好的带隙可调谐能力,纳米薄膜具有较好的光吸收特性,量子点具有多激子产生能力,纳米线具有低反射特性等。重点评述了采用量子阱、纳米薄膜、各种一维纳米结构、纳米晶粒或量子点等不同纳米结构材料,制作的太阳电池的光伏性能及其近年研究进展。指出了各自的潜在优势与存在问题,并提出了设计与制作新型纳米结构太阳电池的若干技术对策,如选择合适的纳米结构材料、制备有序的量子点结构、设计叠层结构等一系列技术手段,借以提高太阳电池的光电转换效率。可以预期,高效率、低成本和长寿命的纳米结构太阳电池将会对未来光伏产业的发展产生重要影响。     

Nanostructured Antimony‐Doped Tin Oxide Layers with Tunable Pore Architectures as Versatile Transparent Current Collectors for Biophotovoltaics

Nanostructured transparent conducting oxide (TCO) layers gain increasing importance as high surface area electrodes enabling incorporation of functional redox species with high loading. The fabrication of porous TCO films, namely, antimony‐doped tin oxide (ATO), is reported using the self‐assembly of preformed ATO nanocrystals with poly(ethylene oxide‐b‐hexyl acrylate) (PEO‐b‐PHA) block copolymer. The high molar mass of the polymer and tunable solution processing conditions enable the fabrication of TCO electrodes with pore sizes ranging from mesopores to macropores. Particularly notable is access to uniform macroporous films with a nominal pore size of around 80 nm, which is difficult to obtain by other techniques. The combination of tunable porosity with a large conducting interface makes the obtained layers versatile current collectors with adjustable performance. While all the obtained electrodes incorporate a large amount of small redox molecules such as molybdenum polyoxometalate, only the electrodes with sufficiently large macropores are able to accommodate high amounts of bulky photoactive photosystem I (PSI) protein complexes. The 11‐fold enhancement of the current response of PSI modified macroporous ATO electrodes compared to PSI on planar indium tin oxide (ITO), makes this type of electrodes promising candidates for the development of biohybrid devices.     

Signal‐On Electrochemiluminescence Biosensors Based on CdS–Carbon Nanotube Nanocomposite for the Sensitive Detection of Choline and Acetylcholine

This work describes for the first time signal‐on electrochemiluminescence (ECL) enzyme biosensors based on cadmium sulfide nanocrystals (CdS NCs) formed in situ on the surface of multi‐walled carbon nanotubes (MWCNTs). The MWCNT–CdS can react with H₂O₂ to generate strong and stable ECL emission in neutral solution. Compared with pure CdS NCs, the MWCNT–CdS can enhance the ECL intensity by 5.3‐fold and move the onset ECL potential more positively for about 400 mV, which reduces H₂O₂ decomposition at the electrode surface and increases detection sensitivity of H₂O₂. Furthermore, the ECL intensity is less influenced by the presence of oxygen in solution. Benefiting from these properties, signal‐on enzyme‐based biosensors are fabricated by cross‐linking choline oxidase and/or acetylcholine esterase with glutaraldehyde on MWCNT–CdS modified electrodes for detection of choline and acetylcholine. The resulting ECL biosensors show wide linear ranges from 1.7 to 332 µM and 3.3 to 216 µM with lower detection limit of 0.8 and 1.7 µM for choline and acetylcholine, respectively. The common interferents such as ascorbic acid and uric acid in electrochemical enzyme‐based biosensors do not interfere with the ECL detection of choline and acetylcholine. Furthermore, both ECL biosensors possess satisfying reproducibility and acceptable stability.     

Micro‐/Nanostructured Highly Crystalline Organic Semiconductor Films for Surface‐Enhanced Raman Spectroscopy Applications

The utilization of inorganic semiconductors for surface‐enhanced Raman spectroscopy (SERS) has attracted enormous interest. However, despite the technological relevance of organic semiconductors for enabling inexpensive, large‐area, and flexible devices via solution processing techniques, these π‐conjugated systems have never been investigated for SERS applications. Here for the first time, a simple and versatile approach is demonstrated for the fabrication of novel SERS platforms based on micro‐/nanostructured 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) thin films via an oblique‐angle vapor deposition. The morphology of C8‐BTBT thin films is manipulated by varying the deposition angle, thus achieving highly favorable 3D vertically aligned ribbon‐like micro‐/nanostructures for a 90° deposition angle. By combining C8‐BTBT semiconductor films with a nanoscopic thin Au layer, remarkable SERS responses are achieved in terms of enhancement (≈10⁸), stability (>90 d), and reproducibility (RSD < 0.14), indicating the great promise of Au/C8‐BTBT films as SERS platforms. Our results demonstrate the first example of an organic semiconductor‐based SERS platform with excellent detection characteristics, indicating that π‐conjugated organic semiconductors have a great potential for SERS applications.     

Fabrication and Characterization of Nanostructured and Thermosensitive Polymer Membranes for Wound Healing and Cell Grafting

Nanostructured, transparent, and thermosensitive membranes synthesized by bicontinuous microemulsion polymerization of N‐isopropylacrylamide (NIPAAm), methyl methacrylate (MMA), and 2‐hydroxyethyl methacrylate (HEMA) using a polymerizable nonionic surfactant, ω‐methoxy poly(ethylene oxide)₄₀ undecyl α‐methacrylate macromonomer have recently been reported. In this study, the synthesis and characterization of membranes with various compositions are presented in detail, focusing on the effects of environmental temperature and membrane composition on surface hydrophilicity, cell attachment, and detachment. The membranes synthesized with differing compositions have a nanoporous structure, and are transparent and thermosensitive in their swelling ratio and cell‐attachment characteristics. Decreasing the environmental temperature and the MMA content leads to an increase in the wettability of the membrane surface. In addition, both L929 murine neoplastic fibroblasts and primary human dermal fibroblasts can attach to and detach from the membranes with varying temperature. High cell‐attachment and ‐detachment efficiencies are achieved by optimizing membrane composition and environmental temperature. In addition, the membranes do not show significant cytotoxicity. These membranes have great potential for the construction of a new generation of dressings and cell‐delivery systems for wound healing.     

The Directional Peeling Effect of Nanostructured Rigiflex Molds on Liquid‐Crystal Devices: Liquid‐Crystal Alignment and Optical Properties

We report a new strategy, the directional peeling of a rigiflex mold with a nanostructure, to overcome several problems with general patterning techniques for liquid‐crystal (LC) alignment. These include difficulty in generating the pretilt angle and in controlling the LC rising‐up direction, formation of local domains, and weak optical properties. The directional peeling of the rigiflex mold results in pretilt‐angle formation and controls the LC rising‐up direction. In addition, a nanostructure with small spacing aligns the LC with a high order parameter because of a strong confinement effect and suppresses diffraction due to its small spacing. Eventually, the nanostructure achieves improvements in the optical properties. In summary, while recent patterning techniques for LC alignment only solve one problem, the directional peeling of the rigiflex mold with a nanostructure simultaneously overcomes several problems with LC alignment and optical properties.     

Incorporation of Functionalized Palladium Nanoparticles within Ultrathin Nafion Films: A Nanostructured Composite for Electrolytic and Redox‐Mediated Hydrogen Evolution

A novel ultrathin Nafion‐palladium nanocomposite film is developed by incorporating positively charged Pd nanoparticles, stabilized with dimethylaminopyridine (DMAP), into Nafion Langmuir‐Schaefer (LS) films. The films show considerable activity for the redox‐catalyzed hydrogen‐evolution reaction, the rate of which scales with film thickness. The Nafion film can be deposited on both insulating (glass) and electrode (indium‐tin oxide) surfaces. The quantity of Pd nanoparticles immobilized can be controlled simply via the thickness of the Nafion film. The morphology of the films are investigated using AFM, which allows the number density of nanoparticles to be estimated for the thinnest (10 layers; 18 nm) films. Incorporation of nanoparticles is also determined with cyclic voltammetry and UV‐visible spectroscopy. The former method allows estimation of the electrochemically active surface area of Pd wired to the underlying electrode. A novel scanning electrochemical microscopy (SECM) approach is used to investigate the kinetics of the hydrogen evolution reaction (HER) catalyzed by Pd nanoparticles within the Nafion film, which allows the intrinsic activity to be determined. Single nanoparticle reactivities are extracted and are comparable to the activity of native nanoparticles on glass and to bulk Pd. It is found that neither Nafion encapsulation nor DMAP functionalization impair the electrocatalytic activity of these nanoparticles towards the HER. Nafion encapsulation thus provides a framework for the formation of interfaces, whose activity scales with film thickness. The creation of 3D materials opens up the possibility of carrying out redox‐mediated hydrogen evolution using solution species as the electron donor.     

A Universal Seeding Strategy to Synthesize Single Atom Catalysts on 2D Materials for Electrocatalytic Applications

Single‐atom catalysts (SACs) are attracting significant attention due to their exceptional catalytic performance and stability. However, the controllable, scalable, and efficient synthesis of SACs remains a significant challenge. Herein, a new and versatile seeding approach is reported to synthesize SACs supported on different 2D materials such as graphene, boron nitride (BN), and molybdenum disulfide (MoS₂). This method is demonstrated on the synthesis of Ni, Co, Fe, Cu, Ag, Pd single atoms as well as binary atoms of Ni and Cu codoped on 2D support materials with the mass loading of single atoms in the range of 2.8–7.9 wt%. In particular, the applicability of the new seeding strategy in electrocatalysis is demonstrate on nickel SACs supported on graphene oxide (SANi‐GO), exhibiting excellent catalytic performance for electrochemical CO₂ reduction reaction with a turnover frequency of 325.9 h^?1 at a low overpotential of 0.63 V and high selectivity of 96.5% for CO production. The facile, controllable, and scalable nature of this approach in the synthesis of SACs is expected to open new research avenues for the practical applications of SACs.     

Gold Nanoparticle–Colloidal Carbon Nanosphere Hybrid Material: Preparation,Characterization, and Application for an Amplified Electrochemical Immunoassay

A rapid microwave‐hydrothermal method has been developed to prepare monodisperse colloidal carbon nanospheres from glucose solution, and gold nanoparticles (AuNPs) are successfully assembled on the surface of the colloidal carbon nanospheres by a self‐assembly approach. The resulting AuNP/colloidal carbon nanosphere hybrid material (AuNP/C) has been characterized and is expected to offer a promising template for biomolecule immobilization and biosensor fabrication because of its satisfactory chemical stability and the good biocompatibility of AuNPs. Herein, as an example, it is demonstrated that the as‐prepared AuNP/C hybrid material can be conjugated with horseradish peroxidase‐labeled antibody (HRP‐Ab₂) to fabricate HRP‐Ab₂‐AuNP/C bioconjugates, which can then be used as a label for the sensitive detection of protein. The amperometric immunosensor fabricated on a carbon nanotube‐modified glass carbon electrode was very effective for antibody immobilization. The approach provided a linear response range between 0.01 and 250 ng mL^?1 with a detection limit of 5.6 pg mL^?1. The developed assay method was versatile, offered enhanced performances, and could be easily extended to other protein detection as well as DNA analysis.     

Pt Nanoparticles Sensitized Ordered Mesoporous WO3 Semiconductor: Gas Sensing Performance and Mechanism Study

In this study, a straightforward coassembly strategy is demonstrated to synthesize Pt sensitized mesoporous WO₃ with crystalline framework through the simultaneous coassembly of amphiphilic poly(ethylene oxide)‐b‐polystyrene, hydrophobic platinum precursors, and hydrophilic tungsten precursors. The obtained WO₃/Pt nanocomposites possess large pore size (≈13 nm), high surface area (128 m² g^?1), large pore volume (0.32 cm³ g^?1), and Pt nanoparticles (≈4 nm) in situ homogeneously distributed in mesopores, and they exhibit excellent catalytic sensing response to CO of low concentration at low working temperature with good sensitivity, ultrashort response‐recovery time (16 s/1 s), and high selectivity. In‐depth study reveals that besides the contribution from the fast diffusion of gaseous molecules and rich interfaces in mesoporous WO₃/Pt nanocomposites, the partially oxidized Pt nanoparticles that chemically and electronically sensitize the crystalline WO₃ matrix, dramatically enhance the sensitivity and selectivity.     

A Reusable Interface Constructed by 3‐Aminophenylboronic Acid‐Functionalized Multiwalled Carbon Nanotubes for Cell Capture,Release, and Cytosensing

A newly developed electrochemical cell sensor for the determination of K562 leukemia cells using 3‐aminophenylboronic acid (APBA)‐functionalized multiwalled carbon nanotubes (MWCNTs) films is demonstrated. The films are generated by the covalent coupling between the ? NH₂ groups in APBA and the ? COOH group in the acid‐oxidized MWCNTs. As a result of the sugar‐specific affinity interactions, the K562 leukemia cells are firmly bound to the APBA‐functionalized MWCNTs film via boronic acid groups. Compared to electropolymerized APBA films, the presence of MWCNTs not only provides abundant boronic acid domains for cell capture, their high electrical conductivity also makes the film suitable for electrochemical sensing applications. The resulting modified electrodes are tested as cell detection sensors. This work presents a promising platform for effective cell capture and constructing reusable cytosensors.     

Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and Viruses

A versatile sensing method based on monodisperse liquid crystal (LC) emulsion droplets detects and distinguishes between different types of bacteria (Gram +ve and ?ve) and viruses (enveloped and non‐enveloped). LCs of 4‐cyano‐4'‐pentylbiphenyl transition from a bipolar to radial configuration when in contact with Gram ?ve bacteria (E. coli) and lipid‐enveloped viruses (A/NWS/Tokyo/67). This transition is consistent with the transfer of lipid from the organisms to the interfaces of the micrometer‐sized LC droplets. In contrast, a transition to the radial configuration is not observed in the presence of Gram +ve bacteria (Bacillus subtilis and Micrococcus luteus) and non‐enveloped viruses (M13 helper phage). The LC droplets can detect small numbers of E. coli bacteria (1–5) and low concentrations (10⁴ pfu mL^?1) of A/NWS/Tokyo/67 virus. Monodisperse LC emulsions incubated with phosholipid liposomes (similar to the E. coli cell wall lipid) reveal that the orientational change is triggered at an area per lipid molecule of ～46 Ų on an LC droplet (～1.6 × 10⁸ lipid molecules per droplet). This approach represents a novel means to sense and differentiate between types of bacteria and viruses based on their cell‐wall/envelope structure, paving the way for the development of a new class of LC microdroplet‐based biological sensors.     

Transparent and Robust Silica Coatings with Dual Range Porosity for Enzyme‐Based Optical Biosensing

Hierarchically porous transparent silica coatings combine large specific surface area with enhanced pore accessibility for optical biosensing. This paper describes a versatile approach to fabricate optically transparent silica coatings with multiscale porosity. Thin films (around 1 μm in thickness) of an aqueous suspension of primary silica aggregates form a mesoporous, interconnected matrix, and sacrificial polymer particles template well‐defined, discrete macropores with high structural integrity. The total surface area achieved is around 200 m² g^?1 with mesopore sizes of 20–40 nm and macropores of 250 nm, with a total porosity of 84%. The macro/meso dual range of porosity allows enhanced biocatalyst loadings of l ‐lactate dehydrogenase for detection of lactate. The functionalized films showed a linear response within the range of interest of 1–20 × 10^?3m of lactate. These biosensing coatings therefore strongly enhance sensitivity, speed and reliability of optically based lactate detection as compared to classical thin films with monomodal mesopore structure. Particle‐based simulations and experiments reveal that both the location and connectivity of the macropores control the biosensing performance. The coatings and procedure presented here are versatile, scalable, inexpensive, and are therefore compatible with a wide range of deposition techniques suitable for industrial and health care applications.     

New Nanostructured TiO2 for Direct Electrochemistry and Glucose Sensor Applications

A new, slack, and uniformly porous TiO₂ material is synthesized by a simple, carbon nanotube (CNT) template‐assisted hydrothermal method and is further explored for protein immobilization and biosensing. Results demonstrate that the material has a large specific surface area and a unique nanostructure with a uniform pore‐size distribution. Glucose oxidase (GOD) immobilized on the material exhibits facile, direct electrochemistry and good electrocatalytic performance without any electron mediator. The fabricated glucose oxidase sensor shows good stability and high sensitivity, which indicates that the slack porous TiO₂ is an attractive material for use in the fabrication of biosensors, particularly enzymatic sensors, because of its direct electrochemistry, high specific surface area, and unique nanostructure for efficient immobilization of biomolecules.     

Branched and Dendritic Polymer Architectures: Functional Nanomaterials for Therapeutic Delivery

Barriers to therapeutic transport in biological systems can prevent accumulation of drugs at the intended site, thus limiting the therapeutic effect against various diseases. Advances in synthetic chemistry techniques have recently increased the accessibility of complex polymer architectures for drug delivery systems, including branched polymer architectures. This article first outlines drug delivery concepts, and then defines and illustrates all forms of branched polymers including highly branched polymers, hyperbranched polymers, dendrimers, and branched–linear hybrid polymers. Many new types of branched and dendritic polymers continue to be reported; however, there is often confusion about how to accurately describe these complex polymer architectures, particularly in the interdisciplinary field of nanomedicine where not all researchers have in‐depth polymer chemistry backgrounds. In this context, the present review describes and compares different branched polymer architectures and their application in therapeutic delivery in a simple and easy‐to‐understand way, with the aim of appealing to a multidisciplinary audience.     

A Smart Nanoprobe Based On Fluorescence‐Quenching PEGylated Nanogels Containing Gold Nanoparticles for Monitoring the Response to Cancer Therapy

A biocompatible, caspase‐3‐responsive, and fluorescence‐quenching smart apoptosis nanoprobe based on a PEGylated nanogel that contains gold nanoparticles (GNPs) (fluorescence quenchers) in the cross‐linked polyamine gel core and fluorescein isothiocyanate (FITC)‐labeled DEVD peptides at the tethered PEG chain ends is prepared for monitoring the cancer response to therapy. FITC–DEVD–nanogel–GNP shows very little fluorescence in the absence of activated caspase‐3 (normal cells) through the fluorescence resonance energy transfer (FRET) process between the GNPs and the FITC molecules, while pronounced fluorescence signals are observed in apoptotic cells because of the cleavage of the DEVD peptide by activated caspase‐3 present in the cells, which results in the release of FITC molecules. Thus, remarkable quenching and dequenching of fluorescence signals in response to activated caspase‐3 is observed. Apoptotic cells are detected in human hepatocyte (HuH‐7) multicellular tumor spheroids (MCTSs), a commonly used three‐dimensional in vitro model mimicking the in vivo biology of tumors, as early as one day post‐treatment with staurosporine, an apoptosis‐inducing agent; while growth inhibition (i.e., change in size) of the HuH‐7 MCTSs is only observed after a delay of three days (i.e., on day 4). This demonstrates the effectiveness of the FITC–DEVD–nanogel–GNP probe as a smart nanoprobe for real‐time monitoring as well as a more rapid assessment of the early response to cancer therapy.     

Nanostructured Hybrid Materials for the Selective Recovery and Enrichment of Rare Earth Elements

The importance of rare‐earth elements (REEs) in the global economy is booming as they are used in numerous advanced technologies. Industrially, the extraction and purification of REEs involve multiple liquid–liquid extraction (LLE) steps as they exhibit very similar complexation properties with most common ligands. In order to substantially improve this process and provide a greener alternative to LLE, functional porous hybrid materials, demonstrating enhanced selectivity towards heavier REEs compared to commercially‐available products, are proposed. In addition, because of the grafting procedure used in the synthesis, the proposed materials demonstrate a higher degree of reusability, increasing their marketable potential.