Functional Inorganic Nanomaterials Research Articles

Recent Advances in Direct Optical Patterning of Inorganic Materials and Devices

AbstractDirect patterning technology holds significant promise owing to its ability to streamline complex patterning processes, fostering affordable design and production of various devices. Direct optical lithographic techniques have recently been applied to diverse ranges of functional inorganic nanomaterials, providing a viable alternative to conventional photolithography. These techniques facilitate the fabrication of diverse thin‐film devices and enable 3D printability for inorganic microarchitectures. This review discusses the recent progress in the direct patterning of inorganic materials and associated device fabrication. The chemical design of inorganic building blocks is delved into, which entails the photochemistry of surface ligands or additives that respond to external stimuli and the different patterning methodologies predicated on these external stimuli. Moreover, device fabrication is introduced through direct patterning methods, highlighting examples from optoelectronic, electronic, and energy devices. Last, the prospects of this field are presented, focusing on materials and processes.

Stimuli-Responsive Surface Ligands for Direct Lithography of Functional Inorganic Nanomaterials.

ConspectusColloidal nanocrystals (NCs) have emerged as a diverse class of materials with tunable composition, size, shape, and surface chemistry. From their facile syntheses to unique optoelectronic properties, these solution-processed nanomaterials are a promising alternative to materials grown as bulk crystals or by vapor-phase methods. However, the integration of colloidal nanomaterials in real-world devices is held back by challenges in making patterned NC films with the resolution, throughput, and cost demanded by device components and applications. Therefore, suitable approaches to pattern NCs need to be established to aid the transition from individual proof-of-concept NC devices to integrated and multiplexed technological systems.In this Account, we discuss the development of stimuli-sensitive surface ligands that enable NCs to be patterned directly with good pattern fidelity while retaining desirable properties. We focus on rationally selected ligands that enable changes in the NC dispersibility by responding to light, electron beam, and/or heat. First, we summarize the fundamental forces between colloidal NCs and discuss the principles behind NC stabilization/destabilization. These principles are applied to understanding the mechanisms of the NC dispersibility change upon stimuli-induced ligand modifications. Six ligand-based patterning mechanisms are introduced: ligand cross-linking, ligand decomposition, ligand desorption, in situ ligand exchange, ion/ligand binding, and ligand-aided increase of ionic strength. We discuss examples of stimuli-sensitive ligands that fall under each mechanism, including their chemical transformations, and address how these ligands are used to pattern either sterically or electrostatically stabilized colloidal NCs. Following that, we explain the rationale behind the exploration of different types of stimuli, as well as the advantages and disadvantages of each stimulus.We then discuss relevant figures-of-merit that should be considered when choosing a particular ligand chemistry or stimulus for patterning NCs. These figures-of-merit pertain to either the pattern quality (e.g., resolution, edge and surface roughness, layer thickness), or to the NC material quality (e.g., photo/electro-luminescence, electrical conductivity, inorganic fraction). We outline the importance of these properties and provide insights on optimizing them. Both the pattern quality and NC quality impact the performance of patterned NC devices such as field-effect transistors, light-emitting diodes, color-conversion pixels, photodetectors, and diffractive optical elements. We also give examples of proof-of-concept patterned NC devices and evaluate their performance. Finally, we provide an outlook on further expanding the chemistry of stimuli-sensitive ligands, improving the NC pattern quality, progress toward 3D printing, and other potential research directions. Ultimately, we hope that the development of a patterning toolbox for NCs will expedite their implementation in a broad range of applications.

CuS Hybrid Hydrogel for Near-Infrared-Enhanced Infected Wound Healing: A Gelatin-Assisted Synthesis and Direct Incorporation Strategy

Developing antibacterial hydrogels, with good mechanical strength and self-healing ability to resist bacterial invasion and accelerate skin regeneration, is critical for infected full-thickness skin wound treatment. Herein, we report a gelatin-assisted synthesis and direct incorporation strategy to construct a CuS hybrid hydrogel for infected wound healing applications. CuS nanodots (NDs) were synthesized directly inside a gelatin host matrix (Gel-CuS), and these tightly confined and evenly distributed CuS NDs displayed superb dispersibility and stability against oxidation. Gel-CuS was then used to crosslink with oxidized dextran (ODex) to form a Gel-CuS-8/ODex hydrogel (8 stands for the concentration of CuS, in mM) via a facile Schiff-base reaction, which exhibited improved mechanical properties, excellent adhesion and self-healing ability, suitable swelling and degradation behavior, and good biocompatibility. The Gel-CuS-8/ODex hydrogel can act as an efficient antibacterial agent due to its photothermal and photodynamic properties under a 1064 nm laser irradiation. Furthermore, in animal experiments, when being applied as wound dressing, the Gel-CuS-8/ODex hydrogel significantly promoted infected full-thickness cutaneous wound healing through improved epidermis and granulation tissue formation and accelerated generation of new blood vessels, hair follicles, and collagen deposition after proper near-infrared irradiation treatment. This work provides a promising strategy to synthesize functional inorganic nanomaterials tightly and evenly embedded inside modified natural hydrogel networks for wound healing applications.

Effective corrosion protection by PDA-BN@CeO2 nanocomposite epoxy coatings

Adding functional inorganic two-dimensional nanomaterials is an effective means to improve the long-term anti-corrosion ability of polymer coatings. Here, due to the mussels’ adhesive ability to various substrates, polydopamine (PDA) was used to modify hexagonal boron nitride (h-BN) and a novel PDA-BN@CeO2 nanohybrid was synthesized through an in situ hydrothermal approach. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) were employed to characterize the as-prepared nanomaterials. The results of salt spray test and electrochemical measurement showed that the composite coatings exhibited a notable superiority in enhancing the anti-corrosion performance, in which the |Z|0.01 Hz was nearly three orders of magnitude higher than that of the neat epoxy coatings when soaked for 35 days. The enhancement mechanism can be attributed to the synergistic effect of BN nanosheets extending the corrosion medium diffusion pathway and CeO2 acting as a corrosion inhibitor to block the contact of corrosion ions with the metal substrate. This study provides a new way for the development of h-BN-based anti-corrosion materials.

Direct Heat-Induced Patterning of Inorganic Nanomaterials.

Patterning functional inorganic nanomaterials is an important process for advanced manufacturing of quantum dot (QD) electronic and optoelectronic devices. This is typically achieved by inkjet printing, microcontact printing, and photo- and e-beam lithography. Here, we investigate a different patterning approach that utilizes local heating, which can be generated by various sources, such as UV-, visible-, and IR-illumination, or by proximity heat transfer. This direct thermal lithography method, termed here heat-induced patterning of inorganic nanomaterials (HIPIN), uses colloidal nanomaterials with thermally unstable surface ligands. We designed several families of such ligands and investigated their chemical and physical transformations responsible for heat-induced changes of nanocrystal solubility. Compared to traditional photolithography using photochemical surface reactions, HIPIN extends the scope of direct optical lithography toward longer wavelengths of visible (532 nm) and infrared (10.6 μm) radiation, which is necessary for patterning optically thick layers (e.g., 1.2 μm) of light-absorbing nanomaterials. HIPIN enables patterning of features defined by the diffraction-limited beam size. Our approach can be used for direct patterning of metal, semiconductor, and dielectric nanomaterials. Patterned semiconductor QDs retain the majority of their as-synthesized photoluminescence quantum yield. This work demonstrates the generality of thermal patterning of nanomaterials and provides a new path for additive device manufacturing using diverse colloidal nanoscale building blocks.

Uniting Drug and Delivery: Metal Oxide Hybrid Nanotherapeutics for Skin Wound Care.

Wound care and soft tissue repair have been a major human concern for millennia. Despite considerable advancements in standards of living and medical abilities, difficult-to-heal wounds remain a major burden for patients, clinicians and the healthcare system alike. Due to an aging population, the rise in chronic diseases such as vascular disease and diabetes, and the increased incidence of antibiotic resistance, the problem is set to worsen. The global wound care market is constantly evolving and expanding, and has yielded a plethora of potential solutions to treat poorly healing wounds. In ancient times, before such a market existed, metals and their ions were frequently used in wound care. In combination with plant extracts, they were used to accelerate the healing of burns, cuts and combat wounds. With the rise of organic chemistry and small molecule drugs and ointments, researchers lost their interest in inorganic materials. Only recently, the advent of nano-engineering has given us a toolbox to develop inorganic materials on a length-scale that is relevant to wound healing processes. The robustness of synthesis, as well as the stability and versatility of inorganic nanotherapeutics gives them potential advantages over small molecule drugs. Both bottom-up and top-down approaches have yielded functional inorganic nanomaterials, some of which unite the wound healing properties of two or more materials. Furthermore, these nanomaterials do not only serve as the active agent, but also as the delivery vehicle, and sometimes as a scaffold. This review article provides an overview of inorganic hybrid nanotherapeutics with promising properties for the wound care field. These therapeutics include combinations of different metals, metal oxides and metal ions. Their production, mechanism of action and applicability will be discussed in comparison to conventional wound healing products.

In Vivo Biosynthesis of Inorganic Nanomaterials Using Eukaryotes-A Review.

Bionanotechnology, the use of biological resources to produce novel, valuable nanomaterials, has witnessed tremendous developments over the past two decades. This eco-friendly and sustainable approach enables the synthesis of numerous, diverse types of useful nanomaterials for many medical, commercial, and scientific applications. Countless reviews describing the biosynthesis of nanomaterials have been published. However, to the best of our knowledge, no review has been exclusively focused on the in vivo biosynthesis of inorganic nanomaterials. Therefore, the present review is dedicated to filling this gap by describing the many different facets of the in vivo biosynthesis of nanoparticles (NPs) using living eukaryotic cells and organisms—more specifically, live plants and living biomass of several species of microalgae, yeast, fungus, mammalian cells, and animals. It also highlights the strengths and weaknesses of the synthesis methodologies and the NP characteristics, bio-applications, and proposed synthesis mechanisms. This comprehensive review also brings attention to enabling a better understanding between the living organisms themselves and the synthesis conditions that allow their exploitation as nanobiotechnological production platforms as these might serve as a robust resource to boost and expand the bio-production and use of desirable, functional inorganic nanomaterials.

Direct Wavelength-Selective Optical and Electron-Beam Lithography of Functional Inorganic Nanomaterials.

Direct optical lithography of functional inorganic nanomaterials (DOLFIN) is a photoresist-free method for high-resolution patterning of inorganic nanocrystals (NCs) that has been demonstrated using deep UV (DUV, 254 nm) photons. Here, we expand the versatility of DOLFIN by designing a series of photochemically active NC surface ligands for direct patterning using various photon energies including DUV, near-UV (i-line, 365 nm), blue (h-line, 405 nm), and visible (450 nm) light. We show that the exposure dose for DOLFIN can be ∼30 mJ/cm2, which is small compared to most commercial photopolymer resists. Patterned nanomaterials can serve as highly robust optical diffraction gratings. We also introduce a general approach for resist-free direct electron-beam lithography of functional inorganic nanomaterials (DELFIN) which enables all-inorganic NC patterns with feature size down to 30 nm, while preserving the optical and electronic properties of patterned NCs. The designed ligand chemistries and patterning techniques offer a versatile platform for nano- and micron-scale additive manufacturing, complementing the existing toolbox for device fabrication.

National University of Singapore (Adv. Mater. 47/2018)

Advanced MaterialsVolume 30, Issue 47 1870354 Cover PictureFree Access National University of Singapore (Adv. Mater. 47/2018) First published: 19 November 2018 https://doi.org/10.1002/adma.201870354AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Graphical Abstract The National University of Singapore (NUS) is a research-intensive university located in the heart of South East Asia. This special issue of Advanced Materials highlights research activities focused on materials science and engineering currently being pursued at NUS. Through outstanding contributions from NUS's research community, this issue presents a multidisciplinary focus on the engineering of functional inorganic, organic, and polymeric nanomaterials, for applications in biomedicine, wearable electronics, photonics, energy, and environmental sustainability. Volume30, Issue47Special Issue: Multidisciplinary Materials Science at the National University of SingaporeNovember 22, 20181870354 RelatedInformation

Large-Scale Syntheses of Zinc Sulfide⋅(Diethylenetriamine)0.5 Hybrids as Precursors for Sulfur Nanocomposite Cathodes.

Nanostructured metal sulfide-amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large-scale synthesis of metal sulfide-amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule-assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5 ) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li-S batteries.

Large‐Scale Syntheses of Zinc Sulfide⋅(Diethylenetriamine)0.5 Hybrids as Precursors for Sulfur Nanocomposite Cathodes

AbstractNanostructured metal sulfide–amine hybrid materials have attracted attention because of their unique properties and versatility as precursors for functional inorganic nanomaterials. However, large‐scale synthesis of metal sulfide–amine hybrid nanomaterials is limited by hydrothermal and solvothermal preparative reaction conditions; consequently, incorporation of such materials into functional nanomaterials is hindered. An amine molecule‐assisted refluxing method was used to synthesize highly uniform zinc sulfide⋅(diethylenetriamine)0.5 (ZnS⋅(DETA)0.5) hybrid nanosheets and nanobelts in a large scale. The obtained ZnS⋅(DETA)0.5 hybrid nanomaterials can be used as efficient precursors to fabricate functional ZnS nanomaterials and carbon encapsulated sulfur (S@C) nanocomposite cathodes for Li–S batteries.

Direct optical lithography of functional inorganic nanomaterials.

Photolithography is an important manufacturing process that relies on using photoresists, typically polymer formulations, that change solubility when illuminated with ultraviolet light. Here, we introduce a general chemical approach for photoresist-free, direct optical lithography of functional inorganic nanomaterials. The patterned materials can be metals, semiconductors, oxides, magnetic, or rare earth compositions. No organic impurities are present in the patterned layers, which helps achieve good electronic and optical properties. The conductivity, carrier mobility, dielectric, and luminescence properties of optically patterned layers are on par with the properties of state-of-the-art solution-processed materials. The ability to directly pattern all-inorganic layers by using a light exposure dose comparable with that of organic photoresists provides an alternate route for thin-film device manufacturing.

ChemInform Abstract: From Solid‐State Metal Alkoxides to Nanostructured Oxides: A Precursor‐Directed Synthetic Route to Functional Inorganic Nanomaterials

AbstractReview: 100 refs.

From solid-state metal alkoxides to nanostructured oxides: a precursor-directed synthetic route to functional inorganic nanomaterials

This review summarizes the construction of nanostructured solid-state metal alkoxides and their conversion into functional inorganic nanomaterials.

High‐Rate Continuous Synthesis of Nanocrystalline Perovskites and Metal Oxides in a Colliding Vapor Stream of Microdroplets

A high‐rate, continuous synthesis of functional nanomaterials using a home engineered reactor is reported. The reactor is able to produce low‐cost, kilogram‐scale BaTiO3 nanopowders with a nanocrystalline particle size less than 30 nm at mild temperatures (<100 °C) and ambient pressure. Nebulization and collision of warm microdroplets (60–80 °C) of Ba(OH)2 and Ti(O‐nBu)4 very quickly result in total hydrolysis and subsequent conversion to BaTiO3, yielding 1.3 kg/day of high purity, highly crystalline nanoparticles (25–30 nm). This synthesis procedure also enables high‐rate production of TiO2 anatase (2.9 kg/day). It therefore provides a general platform for processing and scaling up of functional inorganic nanomaterials under very mild conditions.

Surface-functionalized nanoparticles for biosensing and imaging-guided therapeutics

In this article, the very recent progress of various functional inorganic nanomaterials is reviewed including their unique properties, surface functionalization strategies, and applications in biosensing and imaging-guided therapeutics. The proper surface functionalization renders them with stability, biocompatibility and functionality in physiological environments, and further enables their targeted use in bioapplications after bioconjugation via selective and specific recognition. The surface-functionalized nanoprobes using the most actively studied nanoparticles (i.e., gold nanoparticles, quantum dots, upconversion nanoparticles, and magnetic nanoparticles) make them an excellent platform for a wide range of bioapplications. With more efforts in recent years, they have been widely developed as labeling probes to detect various biological species such as proteins, nucleic acids and ions, and extensively employed as imaging probes to guide therapeutics such as drug/gene delivery and photothermal/photodynamic therapy.

CuOx nanotubes via an unusual complexation induced block copolymer-like self-assembly of poly(acrylic acid)

Polyelectrolyte (PEL) mediated synthesis of functional inorganic nano-materials is attractive due to its versatility and compatibility inside aqueous media. Block copolymers are often employed to facilitate the formation of novel nanostructures. In this work, we report the synthesis of copper oxide (CuOx) crystals with an unexpected hollow nano-tubular morphology using only poly(acrylic acid) (PAA), i.e., a homopolymer. The quantification of the pH dependent binding limit of Cu2+ to PAA, which has often been given little emphasis previously, is found to be critical in understanding the formation mechanism of such nanotubes. Further quantification of the interdependent relationship of pH, α, and [Cu2+] : [COOH]0 using the pKa-α curves provided important insight. The formation of the CuOx nanotubes is believed to be due to an unusual copolymer-like self-assembly of PAA as a homopolymer in aqueous solution; caused by interactions between Cu2+ and charged PAA chains. Such a unique copolymer-like self-assembly behaviour of the PAA–Cu2+ complex manifests within a specific window of [Cu2+] : [COOH]0 ratio around the binding limit. Discussion is also carried out on the possibilities and potential limitations of applying this new concept to other PELs and metal ions.

Transmission electron microscopy as a tool to image bioinorganic nanohybrids: The case of phage‐gold nanocomposites

In recent years, bioinorganic nanohybrids composed of biological macromolecules and functional inorganic nanomaterials have revealed many unique properties that show promise for the future. Transmission electron microscopy (TEM) is a popular and relatively simple tool that can offer a direct visualization of the nanomaterials with high resolutions. When TEM is applied to visualize bioinorganic nanohybrids, a treatment of negative staining is necessary due to the presence of biological molecules in the nanohybrids except for those with densely packed inorganic materials. However, the conventional negative-staining procedure for regular biological samples cannot be directly applied to such bioinorganic nanohybrids. To image a specific bioinorganic nanohybrid, negative-staining factors such as negative stain type, working pH, staining time, and drying method, should be identified. Currently, no detailed studies have been done to investigate how to adjust negative-staining factors based on specific bioinorganic nanohybrids. In this study, bacteriophage-gold nanoparticle hybrids were chosen as a model to systematically study the effects of each factor on the negative staining of the nanohybrids. The best staining conditions for gold nanoparticle-phage nanohybrids were obtained and the effects of each factor on the negative staining of general nanohybrids were discussed. This work indicates that with proper staining it is possible to use TEM to visualize directly both biological and inorganic components without introducing any artifact.

Patterning Nanoparticles by Microcontact Printing and Further Growth of One‐Dimensional Nanomaterials

AbstractA general method for patterning various functional inorganic nanomaterials on SiOx/Si substrates by using microcontact printing (μCP) was developed. The application of hydrophobic poly(dimethylsiloxane) (PDMS) stamps is essential for the reproducibility of this process. By tuning the concentration of the nanoparticle solutions, we can control the thickness of the nanoparticle layers on surfaces. The patterned ZnO nanoparticles on surfaces are used as seeds to grow ZnO nanorod arrays, and the patterned Fe3O4 nanoparticles or Fe/Mo nanoclusters are used as catalysts for the patterned growth of carbon nanotube arrays. This shows that μCP is a facile method to pattern inorganic nanoparticles relying on PDMS stamps of designed surface affinity. Patterned 1Dnanomaterial arrays can subsequently be obtained by use of solution path seeded growth or catalyzed chemical vapor deposition.

Controlled Preparation of Inorganic Nanostructures on Substrates by Dip‐Pen Nanolithography

Controlled preparation of inorganic nanostructures on substrates is very important for various applications of functional inorganic nanomaterials. Dip-pen nanolithography (DPN), as an atomic force microscopy (AFM) based technique, can directly fabricate nanostructures with precise position and morphology control on the nanometer scale and meanwhile image the produced nanostructures in situ at high resolution. This Focus Review summarizes the challenges and progress in preparing inorganic nanostructures with DPN. The ink and reaction design, morphology and structure control, high-speed lithography, and the application of DPN-generated nanopatterns are all involved. The evolution and development of this technique, its superiorities, and unique properties are also discussed.