Green synthesis of metal oxide nanostructures using naturally occurring compounds for energy, environmental, and bio-related applications

This review summarizes the synthesis and functional applications of metal oxide nanostructures synthesized using plant-derived phytochemicals for energy, environmental, and biomedical applications.

Hierarchically ordered structures of disk-cube triads containing hexa-peri-hexabenzocoronene and polyhedral oligomeric silsesquioxane

Obtaining nanoscale-ordered structures is important for the development of nanotechnology. We designed and synthesized a series of disk-cube triads containing one hexa-peri-hexabenzocoronene (HBC) and two polyhedral oligomeric silsesquioxane (POSS) moieties, HBC-2POSS. The two POSS units were linked via ester or amide bonds. With the amide linkage used, the hydrogen bonding that was introduced affected the balance between the π-π interaction of HBC cores and crystallization interaction of POSS units. Hierarchically ordered structures were obtained from HBC-2POSS triads owing to the synergistic effect of multiple secondary interactions: π-π interaction, hydrogen bonding, and crystallization interaction. As organic-inorganic hybrid materials, these HBC-2POSS triads are promising candidates for templates <10 nm.

A Generalizable Top-Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen-Nitrogen Exchange Reaction

A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top-down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen-nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two-step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium-ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom-up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high-performance nanostructured electrode materials that can meet the industrial demand of cost-effectiveness for mass production.

Green, Scalable, and Controllable Fabrication of Nanoporous Silicon from Commercial Alloy Precursors for High-Energy Lithium-Ion Batteries

Silicon is considered as one of the most favorable anode materials for next-generation lithium-ion batteries. Nanoporous silicon is synthesized via a green, facile, and controllable vacuum distillation method from the commercial Mg₂Si alloy. Nanoporous silicon is formed by the evaporation of low boiling point Mg. In this method, the magnesium metal from the Mg₂Si alloy can be recycled. The pore sizes of nanoporous silicon can be secured by adjusting the distillated temperature and time. The optimized nanoporous silicon (800 °C, 0.5 h) delivers a discharge capacity of 2034 mA h g^-1 at 200 mA g^-1 for 100 cycles, a cycling stability with more than 1180 mA h g^-1 even after 400 cycles at 1000 mA g^-1, and a rate capability of 855 mA h g^-1 at 5000 mA g^-1. The electrochemical properties might be ascribed to its porous structure, which may accommodate large volume change during the cycling process. These results suggest that the green, scalable, and controllable approach may offer a pathway for the commercialization of high-performance Si anodes. This method may also be extended to construct other nanoporous materials.

Generation of Well-Defined Micro/Nanoparticles via Advanced Manufacturing Techniques for Therapeutic Delivery

Micro/nanoparticles have great potentials in biomedical applications, especially for drug delivery. Existing studies identified that major micro/nanoparticle features including size, shape, surface property and component materials play vital roles in their in vitro and in vivo applications. However, a demanding challenge is that most conventional particle synthesis techniques such as emulsion can only generate micro/nanoparticles with a very limited number of shapes (i.e., spherical or rod shapes) and have very loose control in terms of particle sizes. We reviewed the advanced manufacturing techniques for producing micro/nanoparticles with precisely defined characteristics, emphasizing the use of these well-controlled micro/nanoparticles for drug delivery applications. Additionally, to illustrate the vital roles of particle features in therapeutic delivery, we also discussed how the above-mentioned micro/nanoparticle features impact in vitro and in vivo applications. Through this review, we highlighted the unique opportunities in generating controllable particles via advanced manufacturing techniques and the great potential of using these micro/nanoparticles for therapeutic delivery.

Optoelectronic fowl adenovirus detection based on local electric field enhancement on graphene quantum dots and gold nanobundle hybrid

An optoelectronic sensor is a rapid diagnostic tool that allows for an accurate, reliable, field-portable, low-cost device for practical applications. In this study, template-free In situ gold nanobundles (Au NBs) were fabricated on an electrode for optoelectronic sensing of fowl adenoviruses (FAdVs). Au NB film was fabricated on carbon electrodes working area using L(+) ascorbic acid, gold chroloauric acid and poly-l-lysine (PLL) through modified layer-by-layer (LbL) method. A scanning electron microscopic (SEM) image of the Au NBs revealed a NB-shaped Au structure with many kinks on its surface, which allow local electric field enhancement through light-matter interaction with graphene quantum dots (GQDs). Here, GQDs were synthesized through an autoclave-assisted method. Characterization experiments revealed blue-emissive, well-dispersed GQDs that were 2-3nm in size with the fluorescence emission peak of GQDs located at 405nm. Both Au NBs and GQDs were conjugated with target FAdVs specific antibodies that bring them close to each other with the addition of target FAdVs through antibody-antigen interaction. At close proximity, light-matter interaction between Au NBs and QDs produces a local electric signal enhancement under Ultraviolet-visible (UV-visible) light irradiation that allows the detection of very low concentrations of target virus even in complex biological media. A proposed optoelectronic sensor showed a linear relationship between the target FAdVs and the electric signal up to 10 Plaque forming unit (PFU)/mL with a limit of detection (LOD) of 8.75 PFU/mL. The proposed sensing strategy was 100 times more sensitive than conventional ELISA method.

Peptide-based biosensors: From self-assembled interfaces to molecular probes in electrochemical assays

Redox-tagged peptides have emerged as functional materials with multiple applications in the area of sensing and biosensing applications due to their high stability, excellent redox properties and versatility of biomolecular interactions. They allow direct observation of molecular interactions in a wide range of affinity and enzymatic assays and act as electron mediators. Short helical peptides possess the ability to self-assemble in specific configurations with the possibility to develop in highly-ordered, stable 1D, 2D and 3D architectures in a hierarchical controlled manner. We provide here a brief overview of the electrochemical techniques available to study the electron transfer in peptide films with particular interest in developing biosensors with immobilized peptide motifs, for biological and clinical applications.

RGD Peptide-Based Target Drug Delivery of Doxorubicin Nanomedicine

Preclinical Research Doxorubicin (DOX) is commonly used for the treatment of breast cancer and lymphoma. However, its clinical use has been severely limited due to cardiotoxicity, requiring the development of safer and more efficient pharmaceutical formulations of DOX. Advances in nanotechnology have provided new ways to administer chemotherapeutic drugs like DOX are conveyed into the body and to tumor sites. These Nanotechnology approaches have aided in the selective accumulation of DOX into tumor sites via the enhanced permeability and retention. However, the absence of active targeting ligands still hinders the effective delivery of DOX. Among all active targeting ligands developed to date, RGD peptide (Arginylglycylaspartic acid) occupies a unique position owing to its inherent safety, biocompatibility, and targeting ability. Accordingly, modification of DOX with RGD ligand is anticipated to improve transport of DOX into tumor cells. In this review, we discuss using RGD peptide for improving the therapeutic efficacy of DOX nanomedicine. Drug Dev Res 78 : 283-291, 2017. © 2017 Wiley Periodicals, Inc.

Tailoring Pore Size and Chemical Interior of near 1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal

A triazine based disc shaped molecule with two hydrolyzable units, imine and ester groups, was polymerized via acyclic diene metathesis in the columnar hexagonal (Colhex) LC phase. Fabrication of a cationic nanoporous polymer (pore diameter ∼1.3 nm) lined with ammonium groups at the pore surface was achieved by hydrolysis of the imine linkage. Size selective aldehyde uptake by the cationic porous polymer was demonstrated. The anilinium groups in the pores were converted to azide as well as phenyl groups by further chemical treatment, leading to porous polymers with neutral functional groups in the pores. The pores were enlarged by further hydrolysis of the ester groups to create ∼2.6 nm pores lined with -COONa surface groups. The same pores could be obtained in a single step without first hydrolyzing the imine linkage. XRD studies demonstrated that the Colhex order of the monomer was preserved after polymerization as well as in both the nanoporous polymers. The porous anionic polymer lined with -COOH groups was further converted to the -COOLi, -COONa, -COOK, -COOCs, and -COONH4 salts. The porous polymer lined with -COONa groups selectively adsorbs a cationic dye, methylene blue, over an anionic dye.

From molecules to macrostructures: recent development of bioinspired hard tissue repair

This review summarizes the bioinspired strategies for hard tissue repair, ranging from molecule-induced mineralization, to microscale assembly to macroscaffold fabrication.

Site-specific control of multiple mineralizations using a designed peptide and DNA

We have developed a site-specific method for precipitating multiple inorganic compounds using target DNA and a designed peptide consisting of a peptide nucleic acid (PNA) sequence and an inorganic compound-precipitating sequence. This system for controlled site-specific precipitation represents a powerful tool for use in nanobiotechnology and materials science.

Site-specific control of silica mineralization on DNA using a designed peptide

We developed a site-specific method for precipitating inorganic compounds using organic compounds, DNA, and designed peptides with peptide nucleic acids (PNAs). Such a system for site-specific precipitation represents a powerful tool for use in nanobiochemistry and materials chemistry.

Recent Advances for Flame Retardancy of Textiles Based on Phosphorus Chemistry

This paper aims at updating the progress on the phosphorus-based flame retardants specifically designed and developed for fibers and fabrics (particularly referring to cotton, polyester and their blends) over the last five years. Indeed, as clearly depicted by Horrocks in a recent review, the world of flame retardants for textiles is still experiencing some changes that are focused on topics like the improvement of its effectiveness and the replacement of toxic chemical products with counterparts that have low environmental impact and, hence, are more sustainable. In this context, phosphorus-based compounds play a key role and may lead, possibly in combination with silicon- or nitrogen-containing structures, to the design of new, efficient flame retardants for fibers and fabrics. Therefore, this review thoroughly describes the advances and the potentialities offered by the phosphorus-based products recently developed at a lab-scale, highlighting the current limitations, open challenges and some perspectives toward their possible exploitation at a larger scale.

Selective Plasma Etching of Polymeric Substrates for Advanced Applications

In today’s nanoworld, there is a strong need to manipulate and process materials on an atom-by-atom scale with new tools such as reactive plasma, which in some states enables high selectivity of interaction between plasma species and materials. These interactions first involve preferential interactions with precise bonds in materials and later cause etching. This typically occurs based on material stability, which leads to preferential etching of one material over other. This process is especially interesting for polymeric substrates with increasing complexity and a “zoo” of bonds, which are used in numerous applications. In this comprehensive summary, we encompass the complete selective etching of polymers and polymer matrix micro-/nanocomposites with plasma and unravel the mechanisms behind the scenes, which ultimately leads to the enhancement of surface properties and device performance.

Bottom-Up Synthesis and Sensor Applications of Biomimetic Nanostructures

The combination of nanotechnology, biology, and bioengineering greatly improved the developments of nanomaterials with unique functions and properties. Biomolecules as the nanoscale building blocks play very important roles for the final formation of functional nanostructures. Many kinds of novel nanostructures have been created by using the bioinspired self-assembly and subsequent binding with various nanoparticles. In this review, we summarized the studies on the fabrications and sensor applications of biomimetic nanostructures. The strategies for creating different bottom-up nanostructures by using biomolecules like DNA, protein, peptide, and virus, as well as microorganisms like bacteria and plant leaf are introduced. In addition, the potential applications of the synthesized biomimetic nanostructures for colorimetry, fluorescence, surface plasmon resonance, surface-enhanced Raman scattering, electrical resistance, electrochemistry, and quartz crystal microbalance sensors are presented. This review will promote the understanding of relationships between biomolecules/microorganisms and functional nanomaterials in one way, and in another way it will guide the design and synthesis of biomimetic nanomaterials with unique properties in the future.

One-dimensional photonic crystals: fabrication, responsiveness and emerging applications in 3D construction

Classical usages of one-dimensional photonic crystals and emerging applications in 3D construction.

Dynamics of formation of Ru, Os, Ir and Au metal nanocrystals on doped graphitic surfaces

The fabrication of precious metal (ruthenium, osmium, gold, and iridium) nanocrystals from single atoms has been studied in real-time.

Facet-Controlled Synthetic Strategy of Cu2O-Based Crystals for Catalysis and Sensing

Shape-dependent catalysis and sensing behaviours are primarily focused on nanocrystals enclosed by low-index facets, especially the three basic facets ({100}, {111}, and {110}). Several novel strategies have recently exploded by tailoring the original nanocrystals to greatly improve the catalysis and sensing performances. In this Review, we firstly introduce the synthesis of a variety of Cu₂O nanocrystals, including the three basic Cu₂O nanocrystals (cubes, octahedra and rhombic dodecahedra, enclosed by the {100}, {111}, and {110} facets, respectively), and Cu₂O nanocrystals enclosed by high-index planes. We then discuss in detail the three main facet-controlled synthetic strategies (deposition, etching and templating) to fabricate Cu₂O-based nanocrystals with heterogeneous, etched, or hollow structures, including a number of important concepts involved in those facet-controlled routes, such as the selective adsorption of capping agents for protecting special facets, and the impacts of surface energy and active sites on reaction activity trends. Finally, we highlight the facet-dependent properties of the Cu₂O and Cu₂O-based nanocrystals for applications in photocatalysis, gas catalysis, organocatalysis and sensing, as well as the relationship between their structures and properties. We also summarize and comment upon future facet-related directions.

λ/20 axial control in 2.5D polymerized structures fabricated with DLW lithography

An astonishing λ/20 height control is accomplished in 2.5D photopolymerized structures by taking advantage of the induced expansion of the resin. Our nanofabrication method is a one-pot approach with two processing steps: (i) regular 2.5D photopolymerization of the resin monomer by using multiphoton direct laser writing (DLW) lithography and (ii) spatially-selective irradiation of the photopolymerized features before development resulting in a nanometer-controlled height increase of the structure. The UV-visible-NIR sub-wavelength axial feature size (~40 nm) of this method allows fabricating devices with applications in multiple technological fields such as nanoelectronics and photonics.

Low-cost fabrication technologies for nanostructures: state-of-the-art and potential

In the last decade, some low-cost nanofabrication technologies used in several disciplines of nanotechnology have demonstrated promising results in terms of versatility and scalability for producing innovative nanostructures. While conventional nanofabrication technologies such as photolithography are and will be an important part of nanofabrication, some low-cost nanofabrication technologies have demonstrated outstanding capabilities for large-scale production, providing high throughputs with acceptable resolution and broad versatility. Some of these nanotechnological approaches are reviewed in this article, providing information about the fundamentals, limitations and potential future developments towards nanofabrication processes capable of producing a broad range of nanostructures. Furthermore, in many cases, these low-cost nanofabrication approaches can be combined with traditional nanofabrication technologies. This combination is considered a promising way of generating innovative nanostructures suitable for a broad range of applications such as in opto-electronics, nano-electronics, photonics, sensing, biotechnology or medicine.

Controllable growth of organic nanostructures from 0D to 1D with different optical properties

Controllable nano/microstructures from 0D to 1D were fabricated by adjusting the growth rate. The difference in symmetry between two molecules results in distinct self-assembly behaviours and different optical properties.

Synthesis of small Fe2O3 nanocubes and their enhanced water vapour adsorption–desorption properties

Uniform ordered Fe₂O₃ nanocubes showed an excellent humidity-controlling ability, due to their appropriate pore size distribution near the condensation critical radius.

The conquest of middle-earth: combining top-down and bottom-up nanofabrication for constructing nanoparticle based devices

The development of top-down nanofabrication techniques has opened many possibilities for the design and realization of complex devices based on single molecule phenomena such as e.g. single molecule electronic devices. These impressive achievements have been complemented by the fundamental understanding of self-assembly phenomena, leading to bottom-up strategies to obtain hybrid nanomaterials that can be used as building blocks for more complex structures. In this feature article we highlight some relevant published work as well as present new experimental results, illustrating the versatility of self-assembly methods combined with top-down fabrication techniques for solving relevant challenges in modern nanotechnology. We present recent developments on the use of hierarchical self-assembly methods to bridge the gap between sub-nanometer and micrometer length scales. By the use of non-covalent self-assembly methods, we show that we are able to control the positioning of nanoparticles on surfaces, and to address the deterministic assembly of nano-devices with potential applications in plasmonic sensing and single-molecule electronics experiments.

Gas sensors based on semiconducting nanowire field-effect transistors

One-dimensional semiconductor nanostructures are unique sensing materials for the fabrication of gas sensors. In this article, gas sensors based on semiconducting nanowire field-effect transistors (FETs) are comprehensively reviewed. Individual nanowires or nanowire network films are usually used as the active detecting channels. In these sensors, a third electrode, which serves as the gate, is used to tune the carrier concentration of the nanowires to realize better sensing performance, including sensitivity, selectivity and response time, etc. The FET parameters can be modulated by the presence of the target gases and their change relate closely to the type and concentration of the gas molecules. In addition, extra controls such as metal decoration, local heating and light irradiation can be combined with the gate electrode to tune the nanowire channel and realize more effective gas sensing. With the help of micro-fabrication techniques, these sensors can be integrated into smart systems. Finally, some challenges for the future investigation and application of nanowire field-effect gas sensors are discussed.

Nanodevices for studying nano-pathophysiology

Nano-scaled devices are a promising platform for specific detection of pathological targets, facilitating the analysis of biological tissues in real-time, while improving the diagnostic approaches and the efficacy of therapies. Herein, we review nanodevice approaches, including liposomes, nanoparticles and polymeric nanoassemblies, such as polymeric micelles and vesicles, which can precisely control their structure and functions for specifically interacting with cells and tissues. These systems have been successfully used for the selective delivery of reporter and therapeutic agents to specific tissues with controlled cellular and subcellular targeting of biomolecules and programmed operation inside the body, suggesting a high potential for developing the analysis for nano-pathophysiology.

Patterned Ni-P alloy films prepared by "reducing-discharging" process and the hydrophobic property

Patterned hydrophobic Ni-P alloy films consisting of orderly and regular micro-nanoscale particles were fabricated through the synergistic effect of electrochemical deposition and chemical deposition. Ni-P alloy films were deposited for different times and characterized by scanning electron microscope (SEM). It was confirmed that the addition of reducing agent induced the formation of nanoscale particles, in contrast with pure Ni film deposited by single electrochemical deposition. As "point-discharge effect", the current density was higher at the edge of the nanoscale particles, and Ni ions would be deposited at the particles through the "point-discharge effect". Then the Ni-P alloy films grew by "reducing-discharging" process. The X-ray photoelectron spectroscopy (XPS) was used to detect the composition and valence states of these alloy films. The existence of oxidation state of element P in these films corresponding to that in H2PO3(-), also gave direct evidence for the occurrence of chemical deposition, during the electrochemical deposition process. The prolongation of deposition time could provide more time for the patterned morphology to grow up. The surface roughness, evaluated by surface profilometer, increased as the deposition time extension. And these films showed gradually increased hydrophobic properties with the increase in deposition time.