Nanomaterials: a membrane-based synthetic approach

Superhydrophobic surfaces and coatings by electrochemical anodic oxidation and plasma electrolytic oxidation

The review provides a comprehensive account of superhydrophobic surfaces fabricated by electrochemical anodic oxidation (anodization). First, reported works on superhydrophobic polymers and metals made by using anodized metal oxide porous templates as moulds are presented (section 2). The next section provides a detailed description of the different fabrication approaches of superhydrophobic surfaces on anodized metallic substrates (section 3.1). The published information on superhydrophobic anodized surfaces in various applications, viz. anti-corrosion, anti-icing, oil separation, and biomedical are systematically covered (section 3.2). Superhydrophobic surfaces fabricated by plasma electrolytic oxidation are also presented (section 4). Future research perspectives debated. The collective information provided is helpful to further advance R & D in making pioneering superhydrophobic anodized nanoporous surfaces.

Quantum Leap from Gold and Silver to Aluminum Nanoplasmonics for Enhanced Biomedical Applications

Nanotechnology has been used in many biosensing and medical applications, in the form of noble metal (gold and silver) nanoparticles and nanostructured substrates. However, the translational clinical and industrial applications still need improvements of the efficiency, selectivity, cost, toxicity, reproducibility, and morphological control at the nanoscale level. In this review, we highlight the recent progress that has been made in the replacement of expensive gold and silver metals with the less expensive aluminum. In addition to low cost, other advantages of the aluminum plasmonic nanostructures include a broad spectral range from deep UV to near IR, providing additional signal enhancement and treatment mechanisms. New synergistic treatments of bacterial infections, cancer, and coronaviruses are envisioned. Coupling with gain media and quantum optical effects improve the performance of the aluminum nanostructures beyond gold and silver.

Template Synthesis of Well-Defined Rutile Nanoparticles by Solid-State Reaction at Room Temperature

Well-defined nanoparticles of rutile (with the size of 5 nm) were successfully prepared by the unusual solid-state transformation of an amorphous precursor in well-defined nanospace of a mesoporous silica template (SBA-15) at room temperature. An aqueous colloidal suspension of the rutile nanoparticles was successfully obtained by dissolution of SBA-15 and subsequent pH adjustment. The isolated rutile nanoparticles were used for H₂ evolution from an aqueous methanol solution by UV irradiation.

Assessing the cyto-genotoxic potential of model zinc oxide nanoparticles in the presence of humic-acid-like-polycondensate (HALP) and the leonardite HA (LHA)

The present study investigates the potential cyto-genotoxic effects of model zinc oxide nanoparticles (ZnO NPs) on human lymphocytes, with and/or without humic acids (HAs). Two types of HAs were studied, a natural well-characterized leonardite HA (LHA) and its synthetic-model, a humic-acid-like-polycondensate (HALP). The Cytokinesis Block Micronucleus (CBMN) assay was applied in cell cultures treated with different concentrations of ZnO NPs (0.5, 5, 10, 20 μg mL^-1) and under different concentrations of either HALP or LHA (ZnO NPs-HALP and ZnO NPs-LHA, at concentrations of 0.5-0.8, 5-8, 10-16, 20-32 and 0.5-2, 5-20, 10-40, 20-80 μg mL^-1, respectively). According to the results, ZnO NPs lacked genotoxicity but demonstrated cytotoxic potential. Binary mixtures of ZnO NPs-HAs (ZnO NPs-HALP or ZnO NPs-LHA) showed negligible alterations of micronuclei (MN) formation in challenged cells, with cytotoxic effects revealed only in case of cells treated with ZnO NPs-LHA at the concentration 5-20 μg mL^-1. Furthermore, no genotoxic phenomena were exerted neither by the ZnO NPs nor from their mixtures with HAs. These findings indicate [i] the cytotoxic activity of used ZnO NPs on human lymphocytes, and [ii] reveal the protective role of HAs against ZnO NPs mediated cytotoxicity.

Functional nanoarrays for investigating stem cell fate and function

Stem cells show excellent potential in the field of tissue engineering and regenerative medicine based on their excellent capability to not only self-renew but also differentiate into a specialized cell type of interest. However, the lack of a non-destructive monitoring system makes it challenging to identify and characterize differentiated cells before their transplantation without compromising cell viability. Thus, the development of a non-destructive monitoring method for analyzing cell function is highly desired and can significantly benefit stem cell-based therapies. Recently, nanomaterial-based scaffolds (e.g., nanoarrays) have made possible considerable advances in controlling the differentiation of stem cells and characterization of the differentiation status sensitively in real time. This review provides a selective overview of the recent progress in the synthesis methods of nanoarrays and their applications in controlling stem cell fate and monitoring live cell functions electrochemically. We believe that the topics discussed in this review can provide brief and concise guidelines for the development of novel nanoarrays and promote the interest in live cell study applications. A method which can not only control but also monitor stem cell fate and function will be a promising technology that can accelerate stem cell therapies.

Single Entity Electrochemistry in Nanopore Electrode Arrays: Ion Transport Meets Electron Transfer in Confined Geometries

Electrochemical measurements conducted in confined volumes provide a powerful and direct means to address scientific questions at the nexus of nanoscience, biotechnology, and chemical analysis. How are electron transfer and ion transport coupled in confined volumes and how does understanding them require moving beyond macroscopic theories? Also, how do these coupled processes impact electrochemical detection and processing? We address these questions by studying a special type of confined-volume architecture, the nanopore electrode array, or NEA, which is designed to be commensurate in size with physical scaling lengths, such as the Debye length, a concordance that offers performance characteristics not available in larger scale structures.The experiments described here depend critically on carefully constructed nanoscale architectures that can usefully control molecular transport and electrochemical reactivity. We begin by considering the experimental constraints that guide the design and fabrication of zero-dimensional nanopore arrays with multiple embedded electrodes. These zero-dimensional structures are nearly ideal for exploring how permselectivity and unscreened ion migration can be combined to amplify signals and improve selectivity by enabling highly efficient redox cycling. Our studies also highlight the benefits of arrays, in that molecules escaping from a single nanopore are efficiently captured by neighboring pores and returned to the population of active redox species being measured, benefits that arise from coupling ion accumulation and migration. These tools for manipulating redox species are well-positioned to explore single molecule and single particle electron transfer events through spectroelectrochemistry, studies which are enabled by the electrochemical zero-mode waveguide (ZMW), a special hybrid nanophotonic/nanoelectronic architecture in which the lower ring electrode of an NEA nanopore functions both as a working electrode to initiate electron transfer reactions and as the optical cladding layer of a ZMW. While the work described here is largely exploratory and fundamental, we believe that the development of NEAs will enable important applications that emerge directly from the unique coupled transport and electron-transfer capabilities of NEAs, including in situ molecular separation and detection with external stimuli, redox-based electrochemical rectification in individually encapsulated nanopores, and coupled sorters and analyzers for nanoparticles.

Light-Activated Heterostructured Nanomaterials for Antibacterial Applications

An outbreak of a bacterial contagion is a critical threat for human health worldwide. Recently, light-activated heterostructured nanomaterials (LAHNs) have shown potential as antibacterial agents, owing to their unique structural and optical properties. Many investigations have revealed that heterostructured nanomaterials are potential antibacterial agents under light irradiation. In this review, we summarize recent developments of light-activated antibacterial agents using heterostructured nanomaterials and specifically categorized those agents based on their various light harvesters. The detailed antibacterial mechanisms are also addressed. With the achievements of LAHNs as antibacterial agents, we further discuss the challenges and opportunities for their future clinical applications.

Effect of thiolate-ligand passivation on the electronic structure and optical absorption properties of ultrathin one and two-dimensional gold nanocrystals

Gold nanomaterials, including one-dimensional (1D) gold nanorods (AuNRs) and nanowires (AuNWs) and two-dimensional (2D) gold nanoprisms with a large surface area and stability, have attracted widespread research interest. A large number of experimental and theoretical studies have shown that the properties of low dimensional gold nanomaterials depend on their anisotropic shape. In this work, we theoretically conceived a new type of gold nanomaterial, namely, thiolate (SR) monolayer passivated quasi-1D and quasi-2D gold nanocrystals and infinite superstructures, which were formed by the fusion of seed clusters Au₂₈(SR)₂₀, Au₃₆(SR)₂₄, Au₄₄(SR)₂₈ and Au₅₂(SR)₃₂ or the layer by layer growth of gold atoms along the [100] and/or [010] directions. By means of DFT and TD-DFT calculations, the structure and properties of these model gold nanocrystals and superstructures are studied in depth. It is found that the passivation of the monolayer of thiolate leads to significantly improved near-infrared absorption properties in comparison with the ligand free gold nanocrystals. Upon passivating the thiolate-monolayer, the ultrathin 1D gold nanowire and 2D gold nanosheet demonstrate a metal to semiconductor transition. The novel electronic structures, optical absorption and semiconductor-to-metal transition found in these thiolate-protected low-dimensional gold nanocrystals suggest that the passivation of the SR ligand is a promising way to tailor the properties of gold nanomaterials.

A facile template-free strategy for synthesizing hydroxymethyl-poly(3,4-ethylenedioxythiophene) nanospheres

Hydroxymethyl-poly(3,4-ethylenedioxythiophene)(PEDOT-OH) nanospheres self-assembled using physical blowing method, which continually used a syringe, were successfully formed through aqueous solution polymerization under the oxidative initiators. The effect of blowing on the morphological properties of PEDOT-OH was precisely evaluated based on the different amount of initiator. The concentration of ammonium persulfate might be a driving force in the self-assembly process to create the PEDOT-OH nanospheres. The electrical and electrochemical properties of the resulting nanospheres were also characterized using four-point probe and cyclic voltammetry.

Soft-Matter Nanotubes: A Platform for Diverse Functions and Applications

Self-assembled organic nanotubes made of single or multiple molecular components can be classified into soft-matter nanotubes (SMNTs) by contrast with hard-matter nanotubes, such as carbon and other inorganic nanotubes. To date, diverse self-assembly processes and elaborate template procedures using rationally designed organic molecules have produced suitable tubular architectures with definite dimensions, structural complexity, and hierarchy for expected functions and applications. Herein, we comprehensively discuss every functions and possible applications of a wide range of SMNTs as bulk materials or single components. This Review highlights valuable contributions mainly in the past decade. Fifteen different families of SMNTs are discussed from the viewpoints of chemical, physical, biological, and medical applications, as well as action fields (e.g., interior, wall, exterior, whole structure, and ensemble of nanotubes). Chemical applications of the SMNTs are associated with encapsulating materials and sensors. SMNTs also behave, while sometimes undergoing morphological transformation, as a catalyst, template, liquid crystal, hydro-/organogel, superhydrophobic surface, and micron size engine. Physical functions pertain to ferro-/piezoelectricity and energy migration/storage, leading to the applications to electrodes or supercapacitors, and mechanical reinforcement. Biological functions involve artificial chaperone, transmembrane transport, nanochannels, and channel reactors. Finally, medical functions range over drug delivery, nonviral gene transfer vector, and virus trap.

Recent development and prospects of surface modification and biomedical applications of MXenes

MXenes, as a novel kind of two-dimensional (2D) materials, were first discovered by Gogotsi et al. in 2011. Owing to their multifarious chemical compositions and outstanding physicochemical properties, the novel types of 2D materials have attracted intensive research interest for potential applications in various fields such as energy storage and conversion, environmental remediation, catalysis, and biomedicine. Although many achievements have been made in recent years, there still remains a lack of reviews to summarize these recent advances of MXenes, especially in biomedical fields. Understanding the current status of surface modification, biomedical applications and toxicity of MXenes and related materials will give some inspiration to the development of novel methods for the preparation of multifunctional MXene-based materials and promote the practical biomedical applications of MXenes and related materials. In this review, we present the recent developments in the surface modification of MXenes and the biomedical applications of MXene-based materials. In the first section, some typical surface modification strategies were introduced and the related issues were also discussed. Then, the potential biomedical applications (such as biosensor, biological imaging, photothermal therapy, drug delivery, theranostic nanoplatforms, and antibacterial agents) of MXenes and related materials were summarized and highlighted in the following sections. In the last section, the toxicity and biocompatibility of MXenes in vitro were mentioned. Finally, the development, future directions and challenges about the surface modification of MXene-based materials for biomedical applications were discussed. We believe that this review article will attract great interest from the scientists in materials, chemistry, biomedicine and related fields and promote the development of MXenes and related materials for biomedical applications.

Recent advances in soft functional materials: preparation, functions and applications

Synthetic materials and biomaterials with elastic moduli lower than 10 MPa are generally considered as soft materials. Research studies on soft materials have been boosted due to their intriguing features such as light-weight, low modulus, stretchability, and a diverse range of functions including sensing, actuating, insulating and transporting. They are ideal materials for applications in smart textiles, flexible devices and wearable electronics. On the other hand, benefiting from the advances in materials science and chemistry, novel soft materials with tailored properties and functions could be prepared to fulfil the specific requirements. In this review, the current progress of soft materials, ranging from materials design, preparation and application are critically summarized based on three categories, namely gels, foams and elastomers. The chemical, physical and electrical properties and the applications are elaborated. This review aims to provide a comprehensive overview of soft materials to researchers in different disciplines.

Holographic detection of nanoparticles using acoustically actuated nanolenses

The optical detection of nanoparticles, including viruses and bacteria, underpins many of the biological, physical and engineering sciences. However, due to their low inherent scattering, detection of these particles remains challenging, requiring complex instrumentation involving extensive sample preparation methods, especially when sensing is performed in liquid media. Here we present an easy-to-use, high-throughput, label-free and cost-effective method for detecting nanoparticles in low volumes of liquids (25 nL) on a disposable chip, using an acoustically actuated lens-free holographic system. By creating an ultrasonic standing wave in the liquid sample, placed on a low-cost glass chip, we cause deformations in a thin liquid layer (850 nm) containing the target nanoparticles (≥140 nm), resulting in the creation of localized lens-like liquid menisci. We also show that the same acoustic waves, used to create the nanolenses, can mitigate against non-specific, adventitious nanoparticle binding, without the need for complex surface chemistries acting as blocking agents.

A Review on Cancer Therapy Based on the Photothermal Effect of Gold Nanorod

Background:

Cancer causes millions of deaths and huge economic losses every year. The currently practiced methods for cancer therapy have many defects, such as side effects, low curate rate, and discomfort for patients.

Objective:

Herein, we summarize the applications of gold nanorods (AuNRs) in cancer therapy based on their photothermal effect-the conversion of light into local heat under irradiation.

Methods:

The recent advances in the synthesis and regulation of AuNRs, and facile surface functionalization further facilitate their use in cancer treatment. For cancer therapy, AuNRs need to be modified or coated with biocompatible molecules (e.g. polyethylene glycol) and materials (e.g. silicon) to reduce the cytotoxicity and increase their biocompatibility, stability, and retention time in the bloodstream. The accumulation of AuNRs in cancerous cells and tissues is due to the high leakage in tumors or the specific interaction between the cell surface and functional molecules on AuNRs such as antibodies, aptamers, and receptors.

Results:

AuNRs are employed not only as therapeutics to ablate tumors solely based on the heat produced under laser that could denature protein and activate the apoptotic pathway, but also as synergistic therapies combined with photodynamic therapy, chemotherapy, and gene therapy to kill cancer more efficiently. More importantly, other materials like TiO2, graphene oxide, and silicon, etc. are incorporated on the AuNR surface for multimodal cancer treatment with high drug loadings and improved cancer-killing efficiency. To highlight their applications in cancer treatment, examples of therapeutic effects both in vitro and in vivo are presented.

Conclusion:

AuNRs have potential applications for clinical cancer therapy.

Electrochemical Manipulation of Aligned Block Copolymer Templates

Block copolymers have a wide range of functions in advanced electrochemistry because of their ability to self-assemble into ordered nanometer-sized structures, resulting in their extensive usage as nanoporous templates that can be electrochemically manipulated. These highly ordered nanoporous templates are used as working electrodes for electrodeposition and electropolymerization to build nanoelectrode arrays and can serve as models to study the diffusion pathway of redox-active units with regard to chemical modification of pores. The block copolymer system allows different morphologies to be utilized, but the most exploited structures are standing cylinders of the minority block that are etched to expose highly aligned porous nanoelectrode array templates. This review starts with introducing alumina and track-etched membranes as pioneer porous templates transitioning to the production of block copolymer films as succeeding templates, with a particular focus on both poly(styrene)-block-poly(methylmethacrylate) (PS-b-PMMA) and poly(styrene)-block-poly(lactide) (PS-b-PLA). The aim is to give fundamental insights of electrochemistry where functionality extends beyond to applications in the nanoscience field of biosensors and plastic electronics.

Plasmonic Metamaterials for Nanochemistry and Sensing

Plasmonic nanostructures were initially developed for sensing and nanophotonic applications but, recently, have shown great promise in chemistry, optoelectronics, and nonlinear optics. While smooth plasmonic films, supporting surface plasmon polaritons, and individual nanostructures, featuring localized surface plasmons, are easy to fabricate and use, the assemblies of nanostructures in optical antennas and metamaterials provide many additional advantages related to the engineering of the mode structure (and thus, optical resonances in the given spectral range), field enhancement, and local density of optical states required to control electronic and photonic interactions. Focusing on two of the many applications of plasmonic metamaterials, in this Account, we review our work on the sensing and nanochemistry applications of metamaterials based on the assemblies of plasmonic nanorods under optical, as well as electronic interrogation. Sensors are widely employed in modern technology for the detection of events or changes in their local environment. Compared to their electronic counterparts, optical sensors offer a combination of high sensitivity, fast response, immunity to electromagnetic interference, and provide additional options for signal retrieval, such as optical intensity, spectrum, phase, and polarization. Owing to the ability to confine and enhance electromagnetic fields on subwavelength scales, plasmonics has been attracting increasing attention for the development of optical sensors with advantages including both nanometer-scale spatial resolution and single-molecule sensitivity. Inherent hot-electron generation in plasmonic nanostructures under illumination or during electron tunneling in the electrically biased nanostructures provides further opportunities for sensing and stimulation of chemical reactions, which would otherwise not be energetically possible. We first provide a brief introduction to a metamaterial sensing platform based on arrays of strongly coupled plasmonic nanorods. Several prototypical sensing examples based on this versatile metamaterial platform are presented. Record-high refractive index sensitivity of gold nanorod arrays in biosensing based on the functionalization of the nanorod surface for selective absorption arises because of the modification of the electromagnetic coupling between the nanorods in the array. The capabilities of nanorod metamaterials for ultrasound and hydrogen sensing were demonstrated by precision coating of the nanorods with functional materials to create core-shell nanostructures. The extension of this metamaterial platform to nanotube and nanocavity arrays, and metaparticles provides additional flexibility and removes restrictions on the illumination configurations for the optical interrogation. We then discuss a nanochemical platform based on the electrically driven metamaterials to stimulate and detect chemical reactions in the tunnel junctions constructed with the nanorods by exploiting elastic tunneling for the activation of chemical reactions via generated hot-electrons and inelastic tunneling for the excitation of plasmons facilitating optical monitoring of the process. This represents a new paradigm merging electronics, plasmonics, photonics and chemistry at the nanoscale, and creates opportunities for a variety of practical applications, such as hot-electron-driven nanoreactors and high-sensitivity sensors, as well as nanoscale light sources and modulators. With a combination of merits, such as the ability to simultaneously support both localized and propagating modes, nanoporous texture, rapid and facile functionalization, and low cost and scalability, plasmonic nanorod metamaterials provide an attractive and versatile platform for the development of optical sensors and nanochemical platforms using hot-electrons with high performance for applications in fundamental research and chemical and pharmaceutical industries.

Multisegmented Metallic Nanorods: Sub-10 nm Growth, Nanoscale Manipulation, and Subwavelength Imaging

Multisegmented metallic nanorods (MS-M-NRs) have attracted increasing attention thanks to their integrated structures and complex functions. The integration of nanoscale segments in 1D enables maximum exposure of each segment and enhanced interaction between adjacent segments. Such structural integration will induce functional complexity in the nanorods, leading to superior properties for the individual components. Herein, recent progress on the development of MS-M-NRs is reviewed. Their precise fabrication, nanoscale manipulation, and subwavelength imaging, as well as simultaneous manipulation and imaging are discussed, respectively. Specifically, precise fabrication of MS-M-NRs focuses on porous anodic alumina (PAA) templated electrodeposition, which enables sub-10 nm growth of the segments and their interfaces/fronts. Nanoscale manipulation of MS-M-NRs introduces the fundamental methods that are employed for delicate movement control on the nanorods through internal or external stimulations. Subwavelength imaging of MS-M-NRs highlights the achievements on identification and location of constituent nanoscale segments/gaps based on their differences and interactions. Simultaneous manipulation and imaging of MS-M-NRs addresses the significance and potential applications of the nanorods with magnetic-plasmonic dual modulation. The development of MS-M-NRs will greatly contribute to materials science and nanoscience/nanotechnology.

Anisotropic nanomaterials for shape-dependent physicochemical and biomedical applications

This review contributes towards a systematic understanding of the mechanism of shape-dependent effects on nanoparticles (NPs) for elaborating and predicting their properties and applications based on the past two decades of research. Recently, the significance of shape-dependent physical chemistry and biomedicine has drawn ever increasing attention. While there has been a great deal of effort to utilize NPs with different morphologies in these fields, so far research studies are largely localized in particular materials, synthetic methods, or biomedical applications, and have ignored the interactional and interdependent relationships of these areas. This review is a comprehensive description of the NP shapes from theory, synthesis, property to application. We figure out the roles that shape plays in the properties of different kinds of nanomaterials together with physicochemical and biomedical applications. Through systematic elaboration of these shape-dependent impacts, better utilization of nanomaterials with diverse morphologies would be realized and definite strategies would be expected for breakthroughs in these fields. In addition, we have proposed some critical challenges and open problems that need to be addressed in nanotechnology.

Nondestructive Characterization of Stem Cell Neurogenesis by a Magneto-Plasmonic Nanomaterial-Based Exosomal miRNA Detection

The full realization of stem cell-based treatments for neurodegenerative diseases requires precise control and characterization of stem cell fate. Herein, we report a multifunctional magneto-plasmonic nanorod (NR)-based detection platform to address the limitations associated with the current destructive characterization methods of stem cell neurogenesis. Exosomes and their inner contents have been discovered to play critical roles in cell-cell interactions and intrinsic cellular regulations and have received wide attention as next-generation biomarkers. Moreover, exosomal microRNAs (miRNA) also offer an essential avenue for nondestructive molecular analyses of cell cytoplasm components. To this end, our developed nondestructive, selective, and sensitive detection platform has (i) an immunomagnetic active component for exosome isolation and (ii) a plasmonic/metal-enhanced fluorescence component for sensitive exosomal miRNA detection to characterize stem cell differentiation. In a proof-of-concept demonstration, our multifunctional magneto-plasmonic NR successfully detected the expression level of miRNA-124 and characterized neurogenesis of human-induced pluripotent stem cell-derived neural stem cells in a nondestructive and efficient manner. Furthermore, we demonstrated the versatility and feasibility of our multifunctional magneto-plasmonic NRs by characterizing a heterogeneous population of neural cells in an ex vivo rodent model. Collectively, we believe our multifunctional magneto-plasmonic NR-based exosomal miRNA detection platform has a great potential to investigate the function of cell-cell interactions and intrinsic cellular regulators for controlling stem cell differentiation.

Self-Limiting Growth of Two-Dimensional Palladium between Graphene Oxide Layers

The ability of different materials to display self-limiting growth has recently attracted an enormous amount of attention because of the importance of nanoscale materials in applications for catalysis, energy conversion, (opto)electronics, and so forth. Here, we show that the electrochemical deposition of palladium (Pd) between graphene oxide (GO) sheets result in the self-limiting growth of 5-nm-thick Pd nanosheets. The self-limiting growth is found to be a consequence of the strong interaction of Pd with the confining GO sheets, which results in the bulk growth of Pd being energetically unfavorable for larger thicknesses. Furthermore, we have successfully carried out liquid exfoliation of the resulting Pd-GO laminates to isolate Pd nanosheets and have demonstrated their high efficiency in continuous flow catalysis and electrocatalysis.

Improving the Stability of Metal Halide Perovskite Quantum Dots by Encapsulation

Metal halide perovskite quantum dots (PQDs), with excellent optical properties and spectacular characteristics of direct and tunable bandgaps, strong light-absorption coefficients, high defect tolerance, and low nonradiative recombination rates, are highly attractive for modern optoelectronic devices. However, the stability issue of PQDs remains a critical challenge of this newly emerged material despite the recent rapid progress. Here, the encapsulation strategies to improve the stability of PQDs are comprehensively reviewed. A special emphasis is put on the effects of encapsulation, ranging from the improvement of chemical stability, to the inhibition of light-induced decomposition, to the enhancement of thermal stability. Particular attention is devoted to summarizing the encapsulation approaches, including the sol-gel method, the template method, physical blending, and microencapsulation. The selection principles of encapsulation materials, including the rigid lattice or porous structure of inorganic compounds, the low penetration rate of oxygen or water, as well as the swelling-deswelling process of polymers, are addressed systematically. Special interest is put on the applications of the encapsulated PQDs with improved stability in white light-emitting diodes, lasers, and biological applications. Finally, the main challenges in encapsulating PQDs and further investigation directions are discussed for future research to promote the development of stable metal halide perovskite materials.

Nanoconfinement of the Low-Temperature Dark Conglomerate: Structural Control from Focal Conics to Helical Nanofilaments

The helical nanofilament (HNF) and low-temperature dark conglomerate (DC) liquid-crystal (LC) phases of bent-core molecules show the same local layer structure but present different bulk morphologies. The DC phase is characterized by the formation of nanoscale toric focal conics, whereas the HNF phase is constructed of bundles of twisted layers. Although the local layer structure is similar in both phases, materials that form these phases tend to form one morphology in preference to the other. Targeted control of the nanostructures would provide pathways to potential applications and insight into how conditions drive a specific phase formation. Here, W624, a compound known to form the DC phase is confined in nanometer scale channels of porous anodized aluminum oxide (AAO) membranes. Within each nanochannel, the DC phase is suppressed forming the HNF structure instead, indicating the nanoscale spatial limitation can control the phase structure of the DC phase.

Plasmonics with Metallic Nanowires

The purpose of this review is to introduce and present the concept of metallic nanowires as building-blocks of plasmonically active structures. In addition to concise description of both the basic physical properties associated with the electron oscillations as well as energy propagation in metallic nanostructures, and methods of fabrication of metallic nanowires, we will demonstrate several key ideas that involve interactions between plasmon excitations and electronic states in surrounding molecules or other emitters. Particular emphasis will be placed on the effects that involve not only plasmonic enhancement or quenching of fluorescence, but also propagation of energy on lengths that exceed the wavelength of light.

Nano-Delivery Materials: Review of Development and Application in Drug/Gene Transport

As the nanotechnology rapidly develops, the combination of nanotechnology and biotechnology to build nanoparticles with biological functionalization has brought new opportunities for the development and application of biomedical diagnosis. Many new non-viral drug/gene vectors were constructed by using nanoparticles as drug/gene carriers, especially by making conventional inorganic materials into nanoparticles and performing functional modifications. In this paper, the physical and chemical properties, preparation methods and application in drug/gene transport of several nanomaterials including mesoporous silica nanoparticles, gold nanoparticles, dendrimers, graphene oxide and carbon nanotubes are reviewed respectively. At the same time, the merit and dismerit of different nanocarriers and their application scenarios are compared. It has been found that the excellent biocompatibility and large specific surface area of inorganic nanomaterials have great potential for drug/gene delivery. Although there are many bottlenecks and challenges for nanomaterials to settle during drug delivery development and industrial production, the improvement of inorganic nanomaterials and the development of new nanocarriers can promote the wider progress of nanocarriers in drug/gene transport.

Magnetically Aligned Nanorods in Alginate Capsules (MANiACs): Soft Matter Tumbling Robots for Manipulation and Drug Delivery

Soft, untethered microrobots composed of biocompatible materials for completing micromanipulation and drug delivery tasks in lab-on-a-chip and medical scenarios are currently being developed. Alginate holds significant potential in medical microrobotics due to its biocompatibility, biodegradability, and drug encapsulation capabilities. Here, we describe the synthesis of MANiACs-Magnetically Aligned Nanorods in Alginate Capsules-for use as untethered microrobotic surface tumblers, demonstrating magnetically guided lateral tumbling via rotating magnetic fields. MANiAC translation is demonstrated on tissue surfaces as well as inclined slopes. These alginate microrobots are capable of manipulating objects over millimeter-scale distances. Finally, we demonstrate payload release capabilities of MANiACs during translational tumbling motion.

A new prototype melt-electrospinning device for the production of biobased thermoplastic sub-microfibers and nanofibers

Sub-microfibers and nanofibers have a high surface-to-volume ratio, which makes them suitable for diverse applications including environmental remediation and filtration, energy production and storage, electronic and optical sensors, tissue engineering, and drug delivery. However, the use of such materials is limited by the low throughput of established manufacturing technologies. This short report provides an overview of current production methods for sub-microfibers and nanofibers and then introduces a new melt-electrospinning prototype based on a spinneret with 600 nozzles, thereby providing an important step towards larger-scale production. The prototype features an innovative collector that achieves the optimal spreading of the fiber due to its uneven surface, as well as a polymer inlet that ensures even polymer distribution to all nozzles. We prepared a first generation of biobased fibers with diameters ranging from 1.000 to 7.000 μm using polylactic acid and 6% (w/w) sodium stearate, but finer fibers could be produced in the future by optimizing the prototype and the composition of the raw materials. Melt electrospinning using the new prototype is a promising method for the production of high-quality sub-microfibers and nanofibers.

Rational Design of Photoelectrodes with Rapid Charge Transport for Photoelectrochemical Applications

Photoelectrode materials are the heart of photoelectrochemical (PEC) cells, which hold great promise to address global energy and environmental issues by converting solar energy into electricity or chemical fuels. In recent decades, significant research efforts have been devoted to the design and construction of photoelectrodes for the efficient generation and utilization of charge carriers to boost PEC performance. Herein, insights from a literature study on the relationship between the architecture and charge dynamics of photoelectrodes are presented. After briefly introducing the fundamental theories of charge dynamics in nanostructured photoelectrodes, the development of photoelectrode design in 1D polycrystalline nanotube arrays, 1D single-crystalline nanowire arrays, and hierarchical and mesoporous nanowire arrays is reviewed with a focus on the interplay between architecture and charge transport properties. For each design, commonly used synthetic approaches and the corresponding charge transport properties are discussed. Subsequently, the applications of these photoelectrodes in PEC systems are summarized. In conclusion, future challenges in the rational design of photoelectrode architecture are presented. The basic relationships between the architectures and charge dynamics of photoelectrode materials discussed here are expected to provide pertinent guidance and a reference for future advanced material design targeting improved light energy conversion systems.

Wettability and Applications of Nanochannels

Wettability in nanochannels is of great importance for understanding many challenging problems in interface chemistry and fluid mechanics, and presents versatile applications including mass transport, catalysis, chemical reaction, nanofabrication, batteries, and separation. Recently, both molecular dynamic simulations and experimental measurements have been employed to study wettability in nanochannels. Here, wettability in three types of nanochannels comprising 1D nanochannels, 2D nanochannels, and 3D nanochannels is summarized both theoretically and experimentally. The proposed concept of "quantum-confined superfluid" for ultrafast mass transport in nanochannels is first introduced, and the mostly studied 1D nanochannels are reviewed from molecular simulation to water wettability, followed by reversible switching of water wettability via external stimuli (temperature and voltage). Liquid transport and two confinement strategies in nanochannels of melt wetting and liquid wetting are also included. Then, molecular simulation, water wettability, liquid transport, and confinement in nanochannels are introduced for 2D nanochannels and 3D nanochannels, respectively. Based on the wettability in nanochannels, broad applications of various nanochannels are presented. Finally, the perspective for future challenges in the wettability and applications of nanochannels is discussed.

Synthesis of calcium-deficient hydroxyapatite nanowires and nanotubes performed by template-assisted electrodeposition

Hydroxyapatite (HA) has received much interest for being used as bone substitutes because of its similarity with bioapatites. In form of nanowires or nanotubes, HA would offer more advantages such as better biological and mechanical properties than conventional particles (spherical). To date, no study had allowed the isolated nanowires production with simultaneously well-controlled morphology and size, narrow size distribution and high aspect ratio (length on diameter ratio). So, it is impossible to determine exactly the real impact of particles' size and aspect ratio on healing responses of bone substitutes and characteristics of these ones; their biological and mechanical effects can never be reproducible. By the template-assisted pulsed electrodeposition method, we have for the first time succeeded to obtain such calcium-deficient hydroxyapatite (CDHA) particles in aqueous baths with hydrogen peroxide by both applying pulsed current density and pulsed potential in cathodic electrodeposition. After determining the best conditions for CDHA synthesis on gold substrate in thin films by X-ray diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDX), we have transferred those conditions to the nanowires and nanotubes synthesis with high aspect ratio going until 71 and 25 respectively. Polycrystalline CDHA nanowires and nanotubes were characterized by Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). At the same time, this study enabled to understand the mechanism of nanopores filling in gold covered polycarbonate membrane: here a preferential nucleation on gold in membranes with 100 and 200 nm nanopores diameters forming nanowires whereas a preferential and randomly nucleation on nanopores walls in membranes with 400 nm nanopores diameter forming nanotubes.

Synthesis and modelling of the mechanical properties of Ag, Au and Cu nanowires

The recent interest to nanotechnology aims not only at device miniaturisation, but also at understanding the effects of quantised structure in materials of reduced dimensions, which exhibit different properties from their bulk counterparts. In particular, quantised metal nanowires made of silver, gold or copper have attracted much attention owing to their unique intrinsic and extrinsic length-dependent mechanical properties. Here we review the current state of art and developments in these nanowires from synthesis to mechanical properties, which make them leading contenders for next-generation nanoelectromechanical systems. We also present theories of interatomic interaction in metallic nanowires, as well as challenges in their synthesis and simulation.

Metal Nanotube/Nanowire-Based Unsupported Network Electrocatalysts

Combining 1D metal nanotubes and nanowires into cross-linked 2D and 3D architectures represents an attractive design strategy for creating tailored unsupported catalysts. Such materials complement the functionality and high surface area of the nanoscale building blocks with the stability, continuous conduction pathways, efficient mass transfer, and convenient handling of a free-standing, interconnected, open-porous superstructure. This review summarizes synthetic approaches toward metal nano-networks of varying dimensionality, including the assembly of colloidal 1D nanostructures, the buildup of nanofibrous networks by electrospinning, and direct, template-assisted deposition methods. It is outlined how the nanostructure, porosity, network architecture, and composition of such materials can be tuned by the fabrication conditions and additional processing steps. Finally, it is shown how these synthetic tools can be employed for designing and optimizing self-supported metal nano-networks for application in electrocatalysis and related fields.