Showing papers in "Nanotechnology in 2019"

A review on ZnO nanostructured materials: energy, environmental and biological applications.

Abstract: Zinc oxide (ZnO) is an adaptable material that has distinctive properties, such as high-sensitivity, large specific area, non-toxicity, good compatibility and a high isoelectric point, which favours it to be considered with a few exceptions. It is the most desirable group of nanostructure as far as both structure and properties. The unique and tuneable properties of nanostructured ZnO shows excellent stability in chemically as well as thermally stable n-type semiconducting material with wide applications such as in luminescent material, supercapacitors, battery, solar cells, photocatalysis, biosensors, biomedical and biological applications in the form of bulk crystal, thin film and pellets. The nanosized materials exhibit higher dissolution rates as well as higher solubility when compared to the bulk materials. This review significantly focused on the current improvement in ZnO-based nanomaterials/composites/doped materials for the application in the field of energy storage and conversion devices and biological applications. Special deliberation has been paid on supercapacitors, Li-ion batteries, dye-sensitized solar cells, photocatalysis, biosensors, biomedical and biological applications. Finally, the benefits of ZnO-based materials for the utilizations in the field of energy and biological sciences are moreover consistently analysed.

Magnetic nanoparticles in nanomedicine: a review of recent advances.

Abstract: Nanomaterials, in addition to their small size, possess unique physicochemical properties that differ from bulk materials, making them ideal for a host of novel applications. Magnetic nanoparticles (MNPs) are one important class of nanomaterials that have been widely studied for their potential applications in nanomedicine. Due to the fact that MNPs can be detected and manipulated by remote magnetic fields, it opens a wide opportunity for them to be used in vivo. Nowadays, MNPs have been used for diverse applications including magnetic biosensing (diagnostics), magnetic imaging, magnetic separation, drug and gene delivery, and hyperthermia therapy, etc. Specifically, we reviewed some emerging techniques in magnetic diagnostics such as magnetoresistive (MR) and micro-Hall (μHall) biosensors, as well as the magnetic particle spectroscopy, magnetic relaxation switching and surface enhanced Raman spectroscopy (SERS)-based bioassays. Recent advances in applying MNPs as contrast agents in magnetic resonance imaging and as tracer materials in magnetic particle imaging are reviewed. In addition, the development of high magnetic moment MNPs with proper surface functionalization has progressed exponentially over the past decade. To this end, different MNP synthesis approaches and surface coating strategies are reviewed and the biocompatibility and toxicity of surface functionalized MNP nanocomposites are also discussed. Herein, we are aiming to provide a comprehensive assessment of the state-of-the-art biological and biomedical applications of MNPs. This review is not only to provide in-depth insights into the different synthesis, biofunctionalization, biosensing, imaging, and therapy methods but also to give an overview of limitations and possibilities of each technology.

Two-dimensional non-layered selenium nanoflakes: facile fabrications and applications for self-powered photo-detector.

Abstract: Two-dimensional (2D) materials exhibit many interesting properties, but most 2D materials are exfoliated from layered bulk materials, limiting the development of the 2D material group. Recently, non-layered 2D materials have aroused great attention due to their excellent catalysis performance, favored compatibility with silicon substrates and high chemical activity. With high photoconductivity, high responsivity and fast response time, non-layered selenium (Se) exhibits important applications in the field of optoelectronics. In this work, we use a simple liquid phase exfoliation method to fabricate 2D Se nanoflakes from bulk Se which possesses a unique chain structure. The thickness of 2D Se nanoflakes was measured to be in the range of 5-10 nm. As-fabricated Se nanoflakes were used in a photodetector by the photoelectrochemical method, showing a high photocurrent density (1.28 μA cm-2) and photoresponsivity (10.45 μA W-1). In addition, the long-term photoelectric measurements indicate that the 2D Se-based photodetector has good time and cycle stability. Our results show that 2D Se has promising potential in liquid-based photo-detectors.

Nanoscale resistive switching memory devices: a review.

Abstract: In this review the different concepts of nanoscale resistive switching memory devices are described and classified according to their I-V behaviour and the underlying physical switching mechanisms. By means of the most important representative devices, the current state of electrical performance characteristics is illuminated in-depth. Moreover, the ability of resistive switching devices to be integrated into state-of-the-art CMOS circuits under the additional consideration with a suitable selector device for memory array operation is assessed. From this analysis, and by factoring in the maturity of the different concepts, a ranking methodology for application of the nanoscale resistive switching memory devices in the memory landscape is derived. Finally, the suitability of the different device concepts for beyond pure memory applications, such as brain inspired and neuromorphic computational or logic in memory applications that strive to overcome the vanNeumann bottleneck, is discussed.

Nonradiating anapole states in nanophotonics: from fundamentals to applications.

Abstract: Nonradiating sources are nontrivial charge-current distributions that do not generate fields outside the source domain. The pursuit of their possible existence has fascinated several generations of physicists and triggered developments in various branches of science ranging from medical imaging to dark matter. Recently, one of the most fundamental types of nonradiating sources, named anapole states, has been realized in nanophotonics regime and soon spurred considerable research efforts and widespread interest. A series of astounding advances have been achieved within a very short period of time, uncovering the great potential of anapole states in many aspects such as lasing, sensing, metamaterials, and nonlinear optics. In this review, we provide a detailed account of anapole states in nanophotonics research, encompassing their basic concepts, historical origins, and new physical effects. We discuss the recent research frontiers in understanding and employing optical anapoles and provide an outlook for this vibrant field of research.

Aggregation effects on the magnetic properties of iron oxide colloids

Abstract: Magnetic nanoparticles (MNPs), and in particular iron oxide nanoparticles (mainly magnetite and maghemite), are being widely used in the form of aqueous colloids for biomedical applications. In such colloids, nanoparticles tend to form assemblies, either aggregates, if the union is permanent, or agglomerates, if it is reversible. These clustering processes have a strong impact on the MNPs' properties that are often not well understood. In this review, the causes and consequences of MNPs aggregation/agglomeration are reviewed and discussed. Special attention has been paid to the impact of the MNPs aggregation/agglomeration on their magnetic properties and heating properties, when exposed to an alternating magnetic field in the frame of magnetic hyperthermia. In addition, a model system with MNPs of two different sizes coated with three different molecules oleic acid, meso-2, 3-dimercaptosuccinic acid and poly(maleic anhydride-alt-1-octadecene) has been characterized and the results used to support the ideas reviewed.

Recent progress in 2D group IV-IV monochalcogenides: synthesis, properties and applications.

Abstract: Coordination-related, 2D structural phase transitions are a fascinating facet of 2D materials with structural degeneracy. Phosphorene and its new phases, exhibiting unique electronic properties, have received considerable attention. The 2D group IV-IV monochalcogenides (i.e. GeS, GeSe, SnS and SnSe) like black phosphorous possess puckered layered orthorhombic structure. The 2D group IV-IV monochalcogenides with advantages of earth-abundance, less toxicity, environmental compatibility and chemical stability, can be widely used in optoelectronics, piezoelectrics, photodetectors, sensors, Li-batteries and thermoelectrics. In this review, we summarized recent research progress in theory and experiment, which studies the fundamental properties, applications and fabrication of 2D group IV-IV monochalcogenides and their new phases, and brings new perspectives and challenges for the future of this emerging field.

Truncated titanium/semiconductor cones for wide-band solar absorbers.

Abstract: A truncated Ti and Si cones metasurface has been proposed for wide-band solar absorber (WSA), which produced a high average absorption of 94.7% in the spectral region from 500 to 4000 nm. A maximal enhancement factor of 166.0% was achieved by the WSA in comparison with the absorption of Ti/Si cylinder resonators based absorber. Under the standard solar radiance, a high full-spectrum solar absorption efficiency of 96.1% was obtained for the WSA in the energy range from 0.28 to 4.0 eV. The spectral bandwidth with absorption above 90% is up to 3.402 μm, which shows an enhancement factor of 165.0% than that of the WSA intercalated by the SiO2. Other semiconductors such as Ge, GaAs have been utilized to form the WSA, which also maintained the near-unity absorption in the wide-band spectrum. The plasmonic resonant response of the Ti material and the strong electromagnetic coupling capability of the Si resonator, and the plasmonic near-field coupling by the adjacent truncated cones were the main contributions for the impressive absorption behaviors. These findings pave a new way for achieving full-spectrum solar absorber via combining the Ti material and semiconductors, which could open potential approaches for active optoelectronic devices such as photo-detectors, hot-electron related modulators, and solar cells, etc.

WS2 and MoS2 thin film gas sensors with high response to NH3 in air at low temperature

Abstract: Transition metal dichalcogenides (TMDs) have received immense research interest in particular for their outstanding electrochemical and optoelectrical properties. Lately, chemical gas sensor applications of TMDs have been recognized as well owing to the low operating temperatures of devices, which is a great advantage over conventional metal oxide based sensors. In this work, we elaborate on the gas sensing properties of WS2 and MoS2 thin films made by simple and straightforward thermal sulfurization of sputter deposited metal films on silicon chips. The sensor response to H2, H2S, CO and NH3 analytes in air at 30 °C has been assessed and both MoS2 and WS2 were found to have an excellent selectivity to NH3 with a particularly high sensitivity of 0.10 ± 0.02 ppm-1 at sub-ppm concentrations in the case of WS2. The sensing behavior is explained on the bases of gas adsorption energies as well as carrier (hole) localization induced by the surface adsorbed moieties having reductive nature.

ZnO nanowires for solar cells: a comprehensive review.

Abstract: As an abundant and non-toxic wide band gap semiconductor with a high electron mobility, ZnO in the form of nanowires (NWs) has emerged as an important electron transporting material in a vast number of nanostructured solar cells. ZnO NWs are grown by low-cost chemical deposition techniques and their integration into solar cells presents, in principle, significant advantages including efficient optical absorption through light trapping phenomena and enhanced charge carrier separation and collection. However, they also raise some significant issues related to the control of the interface properties and to the technological integration. The present review is intended to report a detailed analysis of the state-of-the-art of all types of nanostructured solar cells integrating ZnO NWs, including extremely thin absorber solar cells, quantum dot solar cells, dye-sensitized solar cells, organic and hybrid solar cells, as well as halide perovskite-based solar cells.

Light-weight and low-cost electromagnetic wave absorbers with high performances based on biomass-derived reduced graphene oxides

Abstract: Rational structure design of microwave absorption material is extremely significant from the perspectives of enhancing the electromagnetic microwave absorption (EMA) performance and adapting to cost-effective and sustainable industrial applications. Here, reduced graphene oxides (rGOs) with curl structures derived from corn stover are applied for the absorption of electromagnetic waves. The results suggest that biomass-rGO show the maximum reflection loss of -51.7 dB and an effective absorption bandwidth 13.5 GHz (4.5-18 GHz) at a thickness of 3.25 mm, implying the unique critical role of the microstructure in adjusting the EMA performance. Moreover, the successful conversion of waste biomass into widely used electromagnetic wave absorbing materials could solve the problems of environmental pollution caused by straw burning.

Few-layer bismuthene for femtosecond soliton molecules generation in Er-doped fiber laser

Abstract: Bismuthene, a mono-elemental two-dimensional material with a novel kind of few-layer structure purely consisting of bismuth, has been predicted to have a prominent optical response and enhanced stability in theory. In this paper, few-layer bismuthene is employed as the saturable absorber. The mode-locker is fabricated by dropping bismuthene on a microfiber in a passively mode-locked, Er-doped fiber laser. The single pulse can be obtained at 122.1 mW, with 621.5 fs pulse duration at 1557.5 nm central wavelength, 10.35 nm spectral width and fundamental repetition of 22.74 MHz. Thanks to the outstanding nonlinear effect and semimetal of the bismuthene, dual-pulses, octonary-pulses and fourteen-pulses soliton molecules with tightly and loosely temporal separation can be achieved for the first time, to the best of our knowledge. The preceding indicates that bismuthene will have wide potential in many applications, such as optical fiber communications, optical logical gate, and laser materials processing, etc.

Improving linearity by introducing Al in HfO2 as a memristor synapse device

Abstract: Artificial synapse having good linearity is crucial to achieve an efficient learning process in neuromorphic computing. It is found that the synaptic linearity can be enhanced by engineering the doping region across the switching layer. The nonlinearity of potentiation and depression of the pure device is 36% and 91%, respectively; meanwhile, the nonlinearity after doping can be suppressed to be 22% (potentiation) and 60% (depression). Henceforth, the learning accuracy of the doped device is 91% with only 13 iterations; meanwhile, the pure device is 78%. A detailed conduction mechanism to understand this phenomenon is proposed.

Flexible capacitive pressure sensor with sensitivity and linear measuring range enhanced based on porous composite of carbon conductive paste and polydimethylsiloxane

Abstract: In recent years, the development of electronic skin and smart wearable body sensors has put forward high requirements for flexible pressure sensors with high sensitivity and large linear measuring range. However, it turns out to be difficult to increase both of them simultaneously. In this paper, a flexible capacitive pressure sensor based on a porous carbon conductive paste-polydimethylsiloxane composite is reported, the sensitivity and the linear measuring range of which were developed using multiple methods including adjusting the stiffness of the dielectric layer material, fabricating a microstructure and increasing the dielectric permittivity of the dielectric layer. The capacitive pressure sensor reported here has a relatively high sensitivity of 1.1 kPa-1 and a large linear measuring range of 10 kPa, making the product of the sensitivity and linear measuring range 11, which is higher than that of the most reported capacitive pressure sensors to our best knowledge. The sensor has a detection of limit of 4 Pa, response time of 60 ms and great stability. Some potential applications of the sensor were demonstrated, such as arterial pulse wave measuring and breath measuring, which shows it as a promising candidate for wearable biomedical devices. In addition, a pressure sensor array based on the material was also fabricated and it could identify objects in the shape of different letters clearly, which shows promising application in future electronic skins.

Single and double boron atoms doped nanoporous C2N-h2D electrocatalysts for highly efficient N2 reduction reaction: a density functional theory study.

Abstract: The electrocatalytical process is the most efficient way to produce ammonia (NH3) under ambient conditions, but developing a highly efficient and low-cost metal-free electrocatalysts remains a major scientific challenge. Hence, single atom and double boron (B) atoms doped 2D graphene-like carbon nitride (C2N-h2D) electrocatalysts have been designed (B@C2N and B2@C2N), and the efficiency of N2 reduction reaction (NRR) is examined by density functional theory calculation. The results show that the single and double B atoms can both be strongly embedded in natural nanoporous C2N with superior catalytic activity for N2 activation. The reaction mechanisms of NRR on the B@C2N and B2@C2N are both following an enzymatic pathway, and B2@C2N is a more efficient electrocatalyst with extremely low overpotential of 0.19 eV comparing to B@C2N (0.29 eV). In the low energy region, the hydrogenation of N2 is thermodynamically more favorable than the hydrogen production, thereby improving the selectivity for NRR. Based on these results, a new double-atom strategy may help guiding the experimental synthesis of highly efficient NRR electrocatalysts.

Effect of sulfur doping on fluorescence and quantum yield of graphene quantum dots: an experimental and theoretical investigation.

Abstract: Graphene quantum dots (GQDs) are one of the most promising luminescent carbon derived nanomaterials decorated with multiple useful functional groups and remarkable optoelectronic properties. Heteroatom doping of hexagonal carbon sheet of GQDs is an effective strategy to tailor their properties to meet desired application. In this work, sulfur doped GQDs (S-GQDs) were synthesized by simply pyrolyzing citric acid (CA) as a source of carbon and 3-Mercaptopropionic acid as a source of sulfur dopant. The optimal reaction conditions (ratio of the carbon to dopant source, temperature and time of reaction) were obtained while investigating their effect on the quantum yield and fluorescence properties of GQDs and, are hereby, reported for the first time. The as-synthesized S-GQDs were extensively characterized by different analytical techniques such as transmission electron microscopy (TEM), UV-vis Spectroscopy (UV), Fourier transform infrared spectroscopy, photoluminescence (PL) and x-ray Photoelectron Spectroscopy. S-GQDs were found uniform in size (∼4 nm) and spherical in shape with strong blue fluorescence. Further, for in-depth analysis of experimental results and underlying phenomena, theoretical studies based on density functional theory were performed for chemical structure optimization, possible sites of doping and density of states calculation. The synthesized S-GQDs exhibited excellent solubility in water, a stronger fluorescence and desirably higher quantum yield (57.44%) as compared to that of previously reported undoped GQDs. These successfully demonstrated unique and improved properties of S-GQDs present them as a potential candidate for biomedical, optical, electrical and chemical applications.

Solution-processed metal-oxide thin-film transistors: a review of recent developments.

Abstract: Driven by the rapid development of novel active-matrix displays, thin-film transistors (TFTs) based on metal-oxide (MO) semiconductors have drawn great attention during recent years. N-type MO TFTs manufactured through vacuum-based processes have the advantages of higher mobility compared to the amorphous silicon TFTs, better uniformity and lower processing temperature compared to the polysilicon TFTs, and visible light transparency which is suitable for transparent electronic devices, etc. However, the fabrication cost is high owing to the expensive and complicated vacuum-based systems. In contrast, solution process has the advantages of low cost, high throughput, and easy chemical composition control. In the first part of this review, a brief introduction of solution-processed MO TFTs is given, and the main issues and challenges encountered in this field are discussed. The recent advances in channel layer engineering to obtain the state-of-the-art solution-processed MO TFTs are reviewed and summarized. Afterward, a detailed discussion of the direct patterning methods is presented, including the direct photopatterning and printing techniques. Next, the effect of gate dielectric materials and their interfaces on the performance of the resulting TFTs are surveyed. The last topic is the various applications of solution-processed MO TFTs, from novel displays to sensing, memory devices, etc. Finally, conclusions are drawn and future expectations for solution-processed MO TFTs and their applications are described.

Novel mesoporous electrode materials for symmetric, asymmetric and hybrid supercapacitors.

Abstract: Electrochemical capacitors or supercapacitors have achieved great interest in the recent past due to their potential applications ranging from microelectronic devices to hybrid electric vehicles. Supercapacitors can provide high power densities but their inherently low energy density remains a great challenge. The high-performance supercapacitors utilize large electrode surface area for electrochemical double-layer capacitance and/or pseudocapacitance. To enhance the performance of supercapacitors, various strategies have been adopted such as electrode nanostructuring, hybrid electrode designs using nanocomposite electrodes and hybrid supercapacitor (HSC) configurations. Nanoarchitecturing of electrode-active materials is an effective way of enhancing the performance of supercapacitors as it increases the effective electrode surface area for enhanced electrode/electrolyte interaction. In this review, we focus on the recent developments in the novel electrode materials and various hybrid designs used in supercapacitors for obtaining high specific capacitance and energy density. A family of electrode-active materials including carbon nanomaterials, transition metal-oxides, transition metal-nitrides, transition metal-hydroxides, electronically conducting polymers, and their nanocomposites are discussed in detail. The HSC configurations for attaining enhanced supercapacitor performance as well as strategies to integrate with other microelectronic devices/wearable fabrics are also included.

An overview of photocatalysis facilitated by 2D heterojunctions.

Abstract: Two-dimensional (2D) photocatalysts have attracted considerable research interest in the past decades due to their unique optical, physical and chemical properties. Constructing 2D/2D heterojunctions with large interface area has been considered as an effective approach to enhance the transfer rate and the separation efficiency of the charge carriers, leading to dramatic increase in the photocatalytic performance of the photocatalysts. Here, the state-of-the-art progress on heterojunctions based on 2D materials is reviewed, including the photocatalysis principles using 2D heterojunctions, the categories of 2D heterojunctions and their application in different photocatalytic reactions, and the theoretical studies of the 2D heterojunctions. Moreover, the advantages and disadvantages of the 2D heterojunctions are also discussed. Finally, the ongoing challenges and opportunities for the future development of 2D photocatalysts with built-in heterojunctions are proposed.

Emerging memory technologies for neuromorphic computing.

Abstract: In this paper, we reviewed the recent trends on neuromorphic computing using emerging memory technologies. Two representative learning algorithms used to implement a hardware-based neural network are described as a bio-inspired learning algorithm and software-based learning algorithm, in particular back-propagation. The requirements of the synaptic device to apply each algorithm were analyzed. Then, we reviewed the research trends of synaptic devices to implement an artificial neural network.

Recent progress in the controlled synthesis of 2D metallic transition metal dichalcogenides

Abstract: Two-dimensional (2D) metallic transition metal dichalcogenides (MTMDCs), the complement of 2D semiconducting TMDCs, have attracted extensive attentions in recent years because of their versatile properties such as superconductivity, charge density wave, and magnetism. To promote the investigations of their fantastic properties and broad applications, the preparation of large-area, high-quality, and thickness-tunable 2D MTMDCs has become a very urgent topic and great efforts have been made. This topical review therefore focuses on the introduction of the recent achievements for the controllable syntheses of 2D MTMDCs (VS2, VSe2, TaS2, TaSe2, NbS2, NbSe2, etc). To begin with, some earlier developed routes such as chemical vapor transport, mechanical/chemical exfoliation, as well as molecular beam epitaxy methods are briefly introduced. Secondly, the scalable chemical vapor deposition methods involved with two sorts of metal-based feedstocks, including transition metal chlorides and transition metal oxidations mixed with alkali halides, are discussed separately. Finally, challenges for the syntheses of high-quality 2D MTMDCs are discussed and the future research directions in the related fields are proposed.

Binder free carbon nanofiber electrodes derived from polyacrylonitrile-lignin blends for high performance supercapacitors

Abstract: Lignin was blended with polyacrylonitrile (PAN) in different ratios and fabricated into carbon nanofiber electrodes by electrospinning followed by thermal stabilization, carbonization and subsequent activation by CO2 of the carbonized mats. These carbon fiber electrodes exhibit high surface area, high mesoporosity, high graphitic content and high electrical conductivity. Activated carbon nanofiber mats derived from PAN:Lignin 70:30 blends display a surface area of 2370 m2 g-1 with 0.635 cm3 g-1 mesopore volume. These results are due to the selective partial removal of carbonized lignin during the activation step. Coin cell supercapacitors employing these electrodes exhibit 128 Fg-1 specific capacitance, 59 Wh kg-1 energy density and a 15 kW kg-1 power density when operated at 3.5 V using an ionic liquid electrolyte. Since lignin is an inexpensive, abundant, and green polymer, incorporating it into carbon blends enhances the scalability of such materials in energy storage applications.

Laser micro-structured pressure sensor with modulated sensitivity for electronic skins.

Abstract: Micro-structured pressure sensors with broad pressure sensing range, high sensitivity and rapid response speeds are highly desired for epidermal electronic skin. The widely used methods to fabricate micro-structured pressure sensors are lithography and biomaterial-replicating, which are either complex in preparation procedure or uncontrollable in micro-structure morphology. In this work, laser micro-structured wearable pressure sensors with high-performance are developed for epidermal electronic skin. Laser micro-engineering, with scalability, high-efficiency, and controllability, is employed to prepare a series of micro-structures on elastomers for modulating and enhancing the sensitivity of the sensors. The device with micro-domes owns a sensitivity of -1.82 kPa-1, which is approximately 17 times better than the one based on long micro-ridges. Due to the reduced viscous properties of the elastomers by laser micro-engineering, the sensor based on micro-domes demonstrates rapid response/relaxation speeds of 0.036 and 0.052 s, respectively, and a detection limit of 0.001 kPa. Additionally, the device has a good durability (6,000 cycles) with a repeatability deviation of 1.44%, confirming its stability. Combined with near field communication technology, the sensor has been investigated as epidermal electronic skin for health monitoring.

Porous reduced graphene oxide/nickel foam for highly efficient solar steam generation

Abstract: Solar-driven water evaporation is considered to be an effective method for seawater desalination and wastewater purification. Here, we report a novel solar steam generation (SSG) system based on reduced graphene oxide (rGO)/nickel foam. Porous rGO foam acting as a photothermal conversion layer is fabricated by coating the rGO microsheets on the metallic nickel foam. The porous structure shows a rough surface, which can improve the harvest of light by scattering effect. On the other hand, the porous structure ensures the rapid flow of steam in the evaporation process. This SSG system based on rGO/nickel foam converts the absorbed solar energy into heat energy at the water-air interface and can effectively evaporate (∼83.4%) under low irradiation of 1 sun (1 kw m-2). The system shows great potential for the practical applications of water treatment at large-scale because of the high efficiency, simple preparation method and low cost.

Copper nanoparticles with near-unity, omnidirectional, and broadband optical absorption for highly efficient solar steam generation.

Abstract: Solar steam generation provides a renewable and environmentally friendly approach to solve the water shortage issue. The pursuit of efficient, stable, and cheap photothermal agents is thus of great significance. In this work, Cu nanoparticles (NPs) fabricated simply by a substitution reaction, exhibit a near-unity (~97.7%) light absorption, covering a broad incident angle and wavelength range (200–1300 nm). Thereby, a high photothermal conversion efficiency of 93% is achieved. The excellent photothermal performance offers a unique opportunity for the development of solar steam generation. By coating the Cu NPs on a cellulose membrane, a solar steam generation efficiency up to 73% is acquired at a low irradiation power density of 2 kW m−2 (1 kW m−2 = 1 sun). Moreover, the Cu NPs are recyclable with the high stability being resistant to heat, photoirradiation and corrosion of brine.

High performance supercapacitors using lignin based electrospun carbon nanofiber electrodes in ionic liquid electrolytes.

Abstract: Flexible, free standing and binder-free electrodes were fabricated by electrospinning from a series of lignin: polyvinyl alcohol (PVA) polymer blends, followed by heat treatment. PVA has the dual function of facilitating the electrospinning of lignin and acting as a sacrificial polymer. Upon stabilization, carbonization and CO2 activation, carbon nanofibers (ACNF) derived from the lignin:PVA 80:20 blend displayed a high surface area of 2170 m2 g-1 and a mesopore volume of 0.365 cm3 g-1. ACNFs derived from all the compositions show high degrees of graphitization based on Raman analysis. Pyr14TFSI ionic liquid (IL), modified by mixing with propylene carbonate and ethylene carbonate to reduce the viscosity and increase the ionic conductivity, was used as a high-performance electrolyte. The resulting IL mixture exhibited a four-fold increase in ionic conductivity compared to the neat IL Coin cell supercapacitors using electrodes derived from lignin:PVA 80:20 blends and this electrolyte displayed 87 F g-1 specific capacitance and 38 Wh kg-1 energy density which is the highest reported energy density for lignin:PVA blends to date.

Bifunctional heater-thermometer Nd3+-doped nanoparticles with multiple temperature sensing parameters.

Abstract: Achieving a combination of real-time diagnosis and therapy in a single platform with sensitive thermometry and efficient heat production is a crucial step towards controllable photothermal therapy. Here, Nd3+-doped Y2O3 nanoparticles prepared using the combined Pechini-foaming technique operating in the first and second biological windows were demonstrated as thermal sensors within the wide temperature range of 123-873 K, and as heaters with a temperature increase of 100 K. Thermal sensing was performed based on various approaches: luminescence intensity ratio (electronic levels; Stark sublevels), spectral line position and line bandwidth were used as temperature-dependent parameters. The applicability of these sensing parameters, along with relative thermal sensitivity and temperature resolution, are discussed and compared. The influence of Nd3+-doping concentration on thermometer and heater efficiency was also investigated.

Enhanced extraordinary optical transmission and refractive-index sensing sensitivity in tapered plasmonic nanohole arrays.

Abstract: The phenomenon of extraordinary optical transmission (EOT) caused by light through metallic nanohole arrays has attracted significant attention due to its potential applications for monolithic color filters and ultrasensitive label-free biosensing. However, the EOT spectra of these nanohole arrays have multiple resonance peaks that are spectrally close to each other due to the multiple resonance modes generated by different media on the upper and lower surfaces of metal. In addition, owing to the absorption loss of metal and the scattering of holes, the EOT resonance peaks have low transmission coefficient for practical applications. In this work, utilizing a tapered nanohole arrays structure which is stacked by multiple cylindrical holes with the same depth but different radii, we show that tapered nanohole arrays can effectively suppress the excitation of multiple resonance peaks, and a single EOT peak emerges in the transmission spectrum and simultaneously exhibits significantly enhanced transmission (∼7 times) and narrow linewidth (∼15 nm). The enhanced EOT of tapered nanohole arrays can be also found in other wavelength regions and plasmonic materials. Benefiting from isolated transmission peak, high transmission efficiency and extremely narrow linewidth, a highly sensitive plasmonic nanosensor with sensitivity of 1580 nm/RIU and figure of merit of 105 can be attained. We believe that the tapered nanohole structure would enable applications for ultrasensitive sensors, switches and efficient filters.

Phonon thermal conduction in a graphene-C3N heterobilayer using molecular dynamics simulations.

Abstract: Two-dimensional (2D) graphene (GRA) and polyaniline (C3N) monolayers are attracting growing research interest due to their excellent electrical and thermal properties. In this work, in-plane and out-of-plane phonon thermal conduction of GRA-C3N heterobilayer are systematically investigated by using classical molecular dynamics simulations. Effects of system size, temperature and interlayer coupling strength on the in-plane thermal conductivity (k) and out-of-plane interfacial thermal resistance (R) are evaluated. Firstly, a monotonic increasing trend of k with increasing system size is observed, while a negative correlation between thermal conductivity and temperature is revealed. The interlayer coupling strength is found to have a weak effect on the in-plane thermal conductivity of the heterobilayer. Secondly, at T = 300 K and χ = 1, the predicted R of GRA → C3N and C3N → GRA are 1.29 × 10-7 K m2 W-1 and 1.35 × 10-7 K m2 W-1, respectively, which indicates that there is no significant thermal rectification phenomenon. It can also be observed that R decreases monotonically with increasing temperature and coupling strength due to the enhanced Umklapp phonon scattering and the phonon transmission probability across the interface. Phonon density of states, phonon dispersions and participation ratios are evaluated to reveal the mechanism of heat conduction in the heterobilayer. This work contributes the valuable thermal information to modulate the phonon behaviors in 2D heterobilayer based nanoelectronics.

Tailoring the capability of carbon nitride (C3N) nanosheets toward hydrogen storage upon light transition metal decoration.

Abstract: To nurture the full potential of hydrogen (H2) as a clean energy carrier, its efficient storage under ambient conditions is of great importance. Owing to the potential of material-based H2 storage as a promising option, we have employed here first principles density functional theory calculations to study the H2 storage properties of recently synthesized C3N monolayers. Despite possessing fascinating structural and mechanical properties C3N monolayers weakly bind H2 molecules. However, our van der Waals corrected simulations revealed that the binding properties of H2 on C3N could be enhanced considerably by suitable Sc and Ti doping. The stabilities of Sc and Ti dopants on a C3N surface has been verified by means of reaction barrier calculations and ab initio molecular dynamics simulations. Upon doping with C3N, the existence of partial positive charges on both Sc and Ti causes multiple H2 molecules to bind to the dopants through electrostatic interactions with adsorption energies that are within an ideal range. A drastically high H2 storage capacity of 9.0 wt% could be achieved with two-sided Sc/Ti doping that ensures the promise of C3N as a high-capacity H2 storage material.