Vapor-Tailored Nanojunctions in Ultraporous ZnO Nanoparticle Networks for Superior UV Photodetection.

High quality nanojunctions are known to effectively improve the conductivity and structural robustness of ultraporous nanoparticle networks, surpassing the performance of natural van der Waals interfaces. Nevertheless, the traditional approach of forming these junctions by thermal annealing is incompatible with thermolabile polymers and slender metal electrodes found in modern wearable technologies. Herein, we present a low temperature, solvent vapor-based method to rapidly elicit high-quality metal-oxide nanojunctions in a fast, effortless, inexpensive, and easily scalable process; capable of generating necked interparticle interfaces in a matter of minutes. When applied to ultraporous-based ZnO Ultraviolet (UV) photodetectors, the vapor-tailoring process produces an incredible 128,000-fold improvement in responsivity (6.6 A.W-1) over untreated structures (51.2 µA.W-1), and a 5300-fold improvement in responsivity over thermally annealed structures; all while maintaining exceptionally low dark currents of 140 pA at a low bias voltage of 1 V. Most importantly, the exceptional performance enabled by room temperature synthesis suggests high potential adaptability of this process toward wearable UV sensors, shedding lights on the strategy of modifying weakly bonded porous nanostructures for improved physical properties.

Highly Porous ZnO/CNT Hybrid Microclusters for Superior UV Photodetection.

The formation of nanoscale junctions among nanoparticles in self-assembled nanostructures is crucial for improving both interfacial conductivity and structural integrity. However, the inherent reliance on weak van der Waals forces to hold nanoparticles together poses challenges in developing commercially viable devices due to their inefficient carrier transport characteristics. This study presents the successful integration of carbon nanotubes (CNTs) into highly porous nanomicrocluster arrays of ZnO, resulting in the formation of cohesive and crack-free highly porous ZnO/CNT heterojunction films. This integration marks a significant improvement in UV photodetection performance, demonstrating a record-high photocurrent to dark current ratio of 3.3 × 106 and an exceptional responsivity of 18.5 A/W at a low bias of 0.5 V and under an ultra low light density of 25 µW/cm2. These findings underscore the efficacy of this high-performance structure as a versatile and scalable platform technology for the rapid, cost-effective fabrication of hybrid photodetectors in wearable and portable devices.

Resorbable Membranes for Guided Bone Regeneration: Critical Features, Potentials, and Limitations.

Lack of horizontal and vertical bone at the site of an implant can lead to significant clinical problems that need to be addressed before implant treatment can take place. Guided bone regeneration (GBR) is a commonly used surgical procedure that employs a barrier membrane to encourage the growth of new bone tissue in areas where bone has been lost due to injury or disease. It is a promising approach to achieve desired repair in bone tissue and is widely accepted and used in approximately 40% of patients with bone defects. In this Review, we provide a comprehensive examination of recent advances in resorbable membranes for GBR including natural materials such as chitosan, collagen, silk fibroin, along with synthetic materials such as polyglycolic acid (PGA), polycaprolactone (PCL), polyethylene glycol (PEG), and their copolymers. In addition, the properties of these materials including foreign body reaction, mechanical stability, antibacterial property, and growth factor delivery performance will be compared and discussed. Finally, future directions for resorbable membrane development and potential clinical applications will be highlighted.

Wafer-Scale Growth of Sb2Te3 Films via Low-Temperature Atomic Layer Deposition for Self-Powered Photodetectors.

In this work, we demonstrate the performance of a silicon-compatible, high-performance, and self-powered photodetector. A wide detection range from visible (405 nm) to near-infrared (1550 nm) light was enabled by the vertical p-n heterojunction between the p-type antimony telluride (Sb2Te3) thin film and the n-type silicon (Si) substrates. A Sb2Te3 film with a good crystal quality, low density of extended defects, proper stoichiometry, p-type nature, and excellent uniformity across a 4 in. wafer was achieved by atomic layer deposition at 80 °C using (Et3Si)2Te and SbCl3 as precursors. The processed photodetectors have a low dark current (∼20 pA), a high responsivity of (∼4.3 A/W at 405 nm and ∼150 mA/W at 1550 nm), a peak detectivity of ∼1.65 × 1014 Jones, and a quick rise time of ∼98 µs under zero bias voltage. Density functional theory calculations reveal a narrow, near-direct, type-II band gap at the heterointerface that supports a strong built-in electric field leading to efficient separation of the photogenerated carriers. The devices have long-term air stability and efficient switching behavior even at elevated temperatures. These high-performance and self-powered p-Sb2Te3/n-Si heterojunction photodetectors have immense potential to become reliable technological building blocks for a plethora of innovative applications in next-generation optoelectronics, silicon-photonics, chip-level sensing, and detection.

Recent Advances in Ethylene Gas Detection.

The real-time detecting and monitoring of ethylene gas molecules could benefit the agricultural, horticultural and healthcare industries. In this regard, we comprehensively review the current state-of-the-art ethylene gas sensors and detecting technologies, covering from preconcentrator-equipped gas chromatographic systems, Fourier transform infrared technology, photonic crystal fiber-enhanced Raman spectroscopy, surface acoustic wave and photoacoustic sensors, printable optically colorimetric sensor arrays to a wide range of nanostructured chemiresistive gas sensors (including the potentiometric and amperometric-type FET-, CNT- and metal oxide-based sensors). The nanofabrication approaches, working conditions and sensing performance of these sensors/technologies are carefully discussed, and a possible roadmap for the development of ethylene detection in the near future is proposed.

Nanostructured Gas Sensors: From Air Quality and Environmental Monitoring to Healthcare and Medical Applications.

In the last decades, nanomaterials have emerged as multifunctional building blocks for the development of next generation sensing technologies for a wide range of industrial sectors including the food industry, environment monitoring, public security, and agricultural production. The use of advanced nanosensing technologies, particularly nanostructured metal-oxide gas sensors, is a promising technique for monitoring low concentrations of gases in complex gas mixtures. However, their poor conductivity and lack of selectivity at room temperature are key barriers to their practical implementation in real world applications. Here, we provide a review of the fundamental mechanisms that have been successfully implemented for reducing the operating temperature of nanostructured materials for low and room temperature gas sensing. The latest advances in the design of efficient architecture for the fabrication of highly performing nanostructured gas sensing technologies for environmental and health monitoring is reviewed in detail. This review is concluded by summarizing achievements and standing challenges with the aim to provide directions for future research in the design and development of low and room temperature nanostructured gas sensing technologies.

A network analysis of angiogenesis/osteogenesis-related growth factors in bone tissue engineering based on in-vitro and in-vivo data: A systems biology approach.

The principal purpose of tissue engineering is to stimulate the injured or unhealthy tissues to revive their primary function through the simultaneous use of chemical agents, cells, and biocompatible materials. Still, choosing the appropriate protein as a growth factor (GF) for tissue engineering is vital to fabricate artificial tissues and accelerate the regeneration procedure. In this study, the angiogenesis and osteogenesis-related proteins' interactions are studied using their related network. Three major biological processes, including osteogenesis, angiogenesis, and angiogenesis regulation, were investigated by creating a protein-protein interaction (PPI) network (45 nodes and 237 edges) of bone regeneration efficient proteins. Furthermore, a gene ontology and a centrality analysis were performed to identify essential proteins within a network. The higher degree in this network leads to higher interactions between proteins and causes a considerable effect. The most highly connected proteins in the PPI network are the most remarkable for their employment. The results of this study showed that three significant proteins including prostaglandin endoperoxide synthase 2 (PTGS2), TEK receptor tyrosine kinase (TEK), and fibroblast growth factor 18 (FGF18) were involved simultaneously in osteogenesis, angiogenesis, and their positive regulatory. Regarding the available literature, the results of this study confirmed that PTGS2 and FGF18 could be used as a GF in bone tissue engineering (BTE) applications to promote angiogenesis and osteogenesis. Nevertheless, TEK was not used in BTE applications until now and should be considered in future works to be examined in-vitro and in-vivo.

One-Step Synthesis of Porous Transparent Conductive Oxides by Hierarchical Self-Assembly of Aluminum-Doped ZnO Nanoparticles.

Transparent conductive oxides (TCOs) are highly desirable for numerous applications ranging from photovoltaics to light-emitting diodes and photoelectrochemical devices. Despite progress, it remains challenging to fabricate porous TCOs (pTCOs) that may provide, for instance, a hierarchical nanostructured morphology for the separation of photoexcited hole/electron couples. Here, we present a facile process for the fabrication of porous architectures of aluminum-doped zinc oxide (AZO), a low-cost and earth-abundant transparent conductive oxide. Three-dimensional nanostructured films of AZO with tunable porosities from 10 to 98% were rapidly self-assembled from flame-made nanoparticle aerosols. Successful Al doping was confirmed by X-ray photoemission spectroscopy, high-resolution transmission electron microscopy, elemental mapping, X-ray diffraction, and Fourier transform infrared spectroscopy. An optimal Al-doping level of 1% was found to induce the highest material conductivity, while a higher amount led to partial segregation and formation of aluminum oxide domains. A controllable semiconducting to conducting behavior with a resistivity change of more than 4 orders of magnitudes from about 3 × 102 to 9.4 × 106 Ω cm was observed by increasing the AZO film porosity from 10 to 98%. While the denser AZO morphologies may find immediate application as transparent electrodes, we demonstrate that the ultraporous semiconducting layers have potential as a light-driven gas sensor, showing a high response of 1.92-1 ppm of ethanol at room temperature. We believe that these tunable porous transparent conductive oxides and their scalable fabrication method may provide a highly performing material for future optoelectronic devices.

Nanostructured Gas Sensors for Medical and Health Applications: Low to High Dimensional Materials.

Human breath has long been known as a system that can be used to diagnose diseases. With advancements in modern nanotechnology, gas sensors can now diagnose, predict, and monitor a wide range of diseases from human breath. From cancer to diabetes, the need to treat at the earliest stages of a disease to both increase patient outcomes and decrease treatment costs is vital. Therefore, it is the promising candidate of rapid and non-invasive human breath gas sensors over traditional methods that will fulfill this need. In this review, we focus on the nano-dimensional design of current state-of-the-art gas sensors, which have achieved records in selectivity, specificity, and sensitivity. We highlight the methods of fabrication for these devices and relate their nano-dimensional materials to their record performance to provide a pathway for the gas sensors that will supersede.

Nanostructured Chemiresistive Gas Sensors for Medical Applications.

Treating diseases at their earliest stages significantly increases the chance of survival while decreasing the cost of treatment. Therefore, compared to traditional blood testing methods it is the goal of medical diagnostics to deliver a technique that can rapidly predict and if required non-invasively monitor illnesses such as lung cancer, diabetes, melanoma and breast cancer at their very earliest stages, when the chance of recovery is significantly higher. To date human breath nalysis is a promising candidate for fulfilling this need. Here, we highlight the latest key achievements on nanostructured chemiresistive sensors for disease diagnosis by human breath with focus on the multi-scale engineering of both composition and nano-micro scale morphology. We critically assess and compare state-of-the-art devices with the intention to provide direction for the next generation of chemiresistive nanostructured sensors.

Optimally Hierarchical Nanostructured Hydroxyapatite Coatings for Superior Prosthesis Biointegration.

Bone osteogenesis is a complex phenomenon dependent on numerous microenvironmental cues, with their synchrony regulating cellular functions, such as mechanical signaling, survival, proliferation, and differentiation, as well as controlled regional specification of skeletal progenitor cell fate. Therefore, obtaining a mechanistic understanding of cellular response to a microenvironment is now coming into intense focus, which will facilitate the design of programmable biomaterials for regenerative medicine. State-of-the-art nanomaterial synthesis and self-assembly processes yield complex structures that mimic surface properties, composition, and partially the morphology of the extracellular matrix. However, determining key structural properties that control cell attachment has been challenging and contradictory results are reported regarding the mechanisms and roll of nanostructured materials. Here, we significantly improve osteogenesis on bioinert substrates, demonstrating an exemplary organic-inorganic interface for superior prosthesis biointegration. We identify critical microscale hierarchical features that drastically enhance the cellular response to the same nanoscale architecture. It was observed that hierarchical morphologies, with a porosity above 80%, promote early-stage osteoinduction, as indicated by extensive coating ingrowth and nanofilopodia formation. We determined that cellular integration was mediated by two-way recognition of specific nano- and microtopographical cues between the host tissue and cellular microenvironment. This has allowed us to detail a set of determinant features for the nanofabrication of advanced prosthesis coatings that may ultimately improve implant longevity.

Three-dimensional nano-heterojunction networks: a highly performing structure for fast visible-blind UV photodetectors.

Visible-blind ultraviolet photodetectors are a promising emerging technology for the development of wide bandgap optoelectronic devices with greatly reduced power consumption and size requirements. A standing challenge is to improve the slow response time of these nanostructured devices. Here, we present a three-dimensional nanoscale heterojunction architecture for fast-responsive visible-blind UV photodetectors. The device layout consists of p-type NiO clusters densely packed on the surface of an ultraporous network of electron-depleted n-type ZnO nanoparticles. This 3D structure can detect very low UV light densities while operating with a near-zero power consumption of ca. 4 × 10-11 watts and a low bias of 0.2 mV. Most notably, heterojunction formation decreases the device rise and decay times by 26 and 20 times, respectively. These drastic enhancements in photoresponse dynamics are attributed to the stronger surface band bending and improved electron-hole separation of the nanoscale NiO/ZnO interface. These findings demonstrate a superior structural design and a simple, low-cost CMOS-compatible process for the engineering of high-performance wearable photodetectors.

Low-Voltage High-Performance UV Photodetectors: An Interplay between Grain Boundaries and Debye Length.

Accurate detection of UV light by wearable low-power devices has many important applications including environmental monitoring, space to space communication, and defense. Here, we report the structural engineering of ultraporous ZnO nanoparticle networks for fabrication of very low-voltage high-performance UV photodetectors. A record high photo- to dark-current ratio of 3.3 × 105 and detectivity of 3.2 × 1012 Jones at an ultralow operation bias of 2 mV and low UV-light intensity of 86 µW·cm-2 are achieved by controlling the interplay between grain boundaries and surface depletion depth of ZnO nanoscale semiconductors. An optimal window of structural properties is determined by varying the particle size of ultraporous nanoparticle networks from 10 to 42 nm. We find that small electron-depleted nanoparticles (≤40 nm) are necessary to minimize the dark-current; however, the rise in photocurrent is tampered with decreasing particle size due to the increasing density of grain boundaries. These findings reveal that nanoparticles with a size close to twice their Debye length are required for high photo- to dark-current ratio and detectivity, while further decreasing their size decreases the photodetector performance.

Omnidirectional Self-Assembly of Transparent Superoleophobic Nanotextures.

Engineering surface textures that are highly transparent and repel water, oil, and other low surface energy fluids can transform our interaction with wet environments. Despite extensive progress, current top-down methods are based on directional line-of-sight fabrication mechanisms that are limited by scale and cannot be applied to highly uneven, curved, and enclosed surfaces, while bottom-up techniques often suffer from poor optical transparency. Here, we present an approach that enables the rapid, omnidirectional synthesis of flexible and up to 99.97% transparent superhydrophobic and -oleophobic textures on many variable surface types. These features are obtained by the spontaneous formation of a multi re-entrant morphology during the controlled self-assembly of nanoparticle aerosols. We also develop a mathematical model to explain and control the self-assembly dynamics, providing important insights for the rational engineering of functional materials. We envision that our findings represent a significant advance in imparting superoleophobicity and superamphiphobicity to a so-far inapplicable family of materials and geometries for multifunctional applications.

Flame-made ultra-porous TiO2 layers for perovskite solar cells.

We report methyl ammonium lead iodide (MAPbI3) solar cells with an ultra-porous TiO2 electron transport layer fabricated using sequential flame aerosol and atomic layer depositions of porous and compact TiO2 layers. Flame aerosol pyrolysis allows rapid deposition of nanostructured and ultra-porous TiO2 layers that could be easily scaled-up for high-throughput low-cost industrial solar cell production. An efficiency of 13.7% was achieved with a flame-made nanostructured and ultra-porous TiO2 electrode that was coated with a compact 2 nm TiO2 layer. This demonstrates that MAPbI3 solar cells with a flame-made porous TiO2 layer can have a comparable efficiency to that of the control MAPbI3 solar cell with the well-established spin-coated porous TiO2 layer. The combination of flame aerosol and atomic layer deposition provides precise control of the TiO2 porosity. Notably, the porosity of the as-deposited flame-made TiO2 layers was 97% which was then fine-tuned down to 87%, 56% and 35% by varying the thickness of the subsequent compact TiO2 coating step. The effects of the decrease in porosity on the device performance are discussed. It is also shown that MAPbI3 easily infiltrates into the flame-made porous TiO2 nanostructure thanks to their high porosity and large pore size.

Ultra-Porous Nanoparticle Networks: A Biomimetic Coating Morphology for Enhanced Cellular Response and Infiltration.

Orthopedic treatments are amongst the most common cause of surgery and are responsible for a large share of global healthcare expenditures. Engineering materials that can hasten bone integration will improve the quality of life of millions of patients per year and reduce associated medical costs. Here, we present a novel hierarchical biomimetic coating that mimics the inorganic constituent of mammalian bones with the aim of improving osseointegration of metallic implants. We exploit the thermally-driven self-organization of metastable core-shell nanoparticles during their aerosol self-assembly to rapidly fabricate robust, ultra-porous nanoparticle networks (UNN) of crystalline hydroxyapatite (HAp). Comparative analysis of the response of osteoblast cells to the ultra-porous nanostructured HAp surfaces and to the spin coated HAp surfaces revealed superior osseointegrative properties of the UNN coatings with significant cell and filopodia infiltration. This flexible synthesis approach for the engineering of UNN HAp coatings on titanium implants provides a platform technology to study the bone-implant interface for improved osseointegration and osteoconduction.

Ultraporous superhydrophobic gas-permeable nano-layers by scalable solvent-free one-step self-assembly.

Superhydrophobic materials with excellent humidity tolerance, high porosity and light transmittance are being investigated for numerous applications including moisture-sensitive catalysts and perovskite solar cells. Here, we report the one-step solvent-free synthesis of ultraporous superhydrophobic nano-layers by the on-the-fly functionalization of nanoparticle aerosols. Short exposure of surfaces to hot Mn3O4, ZnO and TiO2 aerosols results in ultraporous nanoparticle networks with repulsive dewetting state approaching ideal Cassie-Baxter superhydrophobicity. In addition to showcasing sliding angles of ca. 0° and very low contact angle hysteresis of 3° ± 2°, these optimal nano-layers have up to 98% porosity and pore size of several micrometres, a key feature to enable efficient penetration of gases to the substrate surface. The stability of this ultraporous superhydrophobic morphology is demonstrated by rapidly applying Moses effect-functionality to substrates that parts water up to 5 mm high. This scalable synthesis method offers a flexible and rapid approach for the production of numerous moisture-resistant devices including gas sensors, catalysts and perovskite solar cells.

Scalable Synthesis of Efficient Water Oxidation Catalysts: Insights into the Activity of Flame-Made Manganese Oxide Nanocrystals.

Chemical energy storage by water splitting is a promising solution for the utilization of renewable energy in numerous currently impracticable needs, such as transportation and high temperature processing. Here, the synthesis of efficient ultra-fine Mn3O4 water oxidation catalysts with tunable specific surface area is demonstrated by a scalable one-step flame-synthesis process. The water oxidation performance of these flame-made structures is compared with pure Mn2O3 and Mn5O8, obtained by post-calcination of as-prepared Mn3O4 (115 m(2) g(-1)), and commercial iso-structural polymorphs, probing the effect of the manganese oxidation state and synthetic route. The structural properties of the manganese oxide nanoparticles were investigated by XRD, FTIR, high-resolution TEM, and XPS. It is found that these flame-made nanostructures have substantially higher activity, reaching up to 350 % higher surface-specific turnover frequency (0.07 µmolO2 m(-2) s(-1)) than commercial nanocrystals (0.02 µmolO2 m(-2) s(-1)), and production of up to 0.33 mmolO2 molMn (-1) s(-1). Electrochemical characterization confirmed the high water oxidation activity of these catalysts with an initial current density of 10 mA cm(-2) achieved with overpotentials between 0.35 and 0.50 V in 1 m NaOH electrolyte.

Ultraporous Electron-Depleted ZnO Nanoparticle Networks for Highly Sensitive Portable Visible-Blind UV Photodetectors.

A hierarchical nano- and microstructured morphology for visible-blind UV photo-detectors is developed, which provides record-high milliampere photocurrents, nanoampere dark currents, and excellent selectivity to ultralow UV light intensities. This is a significant step toward the integration of high-performance UV photodetectors in wearable devices.

Self-assembly dynamics and accumulation mechanisms of ultra-fine nanoparticles.

The self-assembly of nanomaterials into three-dimensional hierarchical structures is a fundamental step impacting a large number of synthetic and natural processes. These range from the scalable fabrication of nano-devices such as batteries, sensors and third generation solar cells to the uptake and accumulation of particulate pollution in the lung alveoli. Here, we show that the Dynamic behavior of ultra-fine particles (UFP < 100 nm) diverges significantly from that of sub- and micro equivalents. For freely diffusing bodies, this leads to the formation of stochastically reproducible films that approach the morphology and density of ballistically deposited ones. A novel deposition mechanism and regime are proposed that successfully capture the full spectrum of size-dependent self-assembly dynamics. These findings are a significant step toward the engineering of scalable parallel nano-fabrication approaches, and the understanding of the interaction of unbound nanostructures with their surrounding.