Table of contents

Self-catalyzed metal organic chemical vapor deposition (MOCVD) growth of Ga₂O₃ nanowires on GaN layers prepared on a sapphire substrate has been studied. Nanowire orientations are found to be growth temperature dominated. The vertical yields over total (VOT) curve shows a maximum peak beyond 70% around 480 °C, based on scanning electron microscope observations. X-ray diffraction patterns revealed a primary β-(-201) normal orientation of as grown nanowires all over the studied temperature interval. Further transmission electron microscopy characterization had confirmed β-(-201) normal axial orientation of these vertical nanowires, which have well crystallinity. The β-(010)//GaN(110) in-plane epitaxial relationship is consistent with reported Ga₂O₃ film/nanowire growth. Nanowires crystallized in β-[001] axial orientation were considered to be the inclined ones. Based on contrast experiments, the temperature dominated growth behavior is considered a thermodynamic process. The two observed crystalline orientation might have distinguishable but similar system energy, which results in coexistence of multi orientation nanowires over a large temperature span and an optimum temperature window for vertical β-(-201) normal orientation. The presented optimized β-Ga₂O₃ nanowire arrays with highest VOT close to 90% should effectively promote development of reliable high performance devices based on Ga₂O₃ nanowires.

Nanostructured mesoporous carbon materials have been an attractive material for electrochemical energy storage in the recent decades. However, the controllable synthesis of two-dimensional mesoporous carbon with tunable thickness and desired pore structure is highly challenging. Here, a series of graphene@mesoporous nitrogen-doped carbon (denoted as G@mesoNC) core–shell structured nanosheets with tunable thicknesses have been fabricated via a sample hydrothermal method by using cellulose as the green and cheap carbon precursor. The resultant G@mesoNC nanosheets exhibit a distinct sandwich-like structure with tunable thicknesses (from 10 to 30 nm), a large surface area (562 m² g⁻¹), a narrow pore size distribution (2.3 nm) and a high nitrogen content (7.95%). Significantly, when being used as the electrode for supercapaciors, the resultant G@mesoNC nanosheets showcase a high specific capacitance of 264 F g⁻¹. Most importantly, there is no substantial capacitance decay after 2500 cycles, indicating the perfect cyclic stability of G@mesoNC nanosheets. Our method paves a new way for synthesizing carbon electrodes for energy storage.

Advances in renewable and sustainable energy technologies critically depend on our ability to rationally design and process target materials with optimized performances. Advanced material design and discovery are ideally involved in material prediction, synthesis and characterization. Control of material crystallization enables the rational design and discovery of novel functional inorganic materials in multi-scale. Material processing can be adjusted by various physical fields and chemical effects at different energy states. Material microstructure, architecture and functionality can thus be modified by multiple design methodologies. In this review, we show typical examples using physical and chemical methods to shape inorganic functional materials and evaluate their specific applications in Na-air batteries, Li-ion batteries and supercapacitors. Furthermore, this review also provides insight into the understanding of synthesis-structure relationship of inorganic functional materials.

GaN has interesting prospects in applications for spectrum-tunable solid-state devices with photoelectric conversion function. Similarly, single nanowires or nanowire arrays (NWAs) proceed to exhibit good photon absorbance and photoemission characteristics as vacuum devices based on the external photoelectric effect. However, the collection of photoelectrons emitted from a nanowire surface has become the greatest impediment to the progress of GaN NWAs photocathodes. In this study, a field-assisted GaN NWA photocathode is proposed. The photoemission efficiency and electron collection efficiency of the field-assisted GaN NWA photocathode are derived. The results suggest that the external field can effectively enhance the photoemission capacity and electron collection efficiency of the photocathode. Based on the theoretical model, the structural parameters of NWAs and the field intensity are optimized. When the field intensity is 1 V μm⁻¹, the collected photocurrent of the GaN NWA photocathode reaches a maximum. For NWAs with an aspect ratio of 1:1, the optimal incident angle of light is 70°. This study provides a theoretical guide for the incorporation of an external field in a GaN NWA photocathode with the purpose of enhancing photoemission and electron collection capacity.

In this paper, we propose a dipole coupled magnetic quantum-dot cellular automata-based approximate nanomagnetic (APN) architectural design approach for subtractor and adder. In addition, we also introduce an APN architecture which offers runtime reconfigurability using a single design layout comprising only four nanomagnets. Subsequently, we propose the APN add/sub architecture by exploiting shape anisotropy and ferromagnetically coupled fixed input majority gate. The proposed APN architecture designs have been implemented using a micromagnetic simulation tool and performance has been compared with the state-of-the-art approach resulting in a ∼50%–80% reduction in the number of nanomagnets and clock cycles without degradation in the accuracy leading to area and energy efficiency.

We have fabricated at wafer level field-effect-transistors (FETs) having as channel graphene monolayers transferred on a HfZrO ferroelectric, grown by atomic layer deposition on a doped Si (100) substrate. These FETs display either horizontal or vertical carrier transport behavior, depending on the applied gate polarity. In one polarity, the FETs behave as a graphene FET where the transport is horizontal between two contacts (drain and grounded source) and is modulated by a back-gate. Changing the polarity, the transport is vertical between the drain and the back-gate and, irrespective of the metallic contact type, Ti/Au or Cr/Au, the source–drain bias modulates the height of the potential barrier between HfZrO and the doped Si substrate, the carrier transport being described by a Schottky mechanism at high gate voltages and by a space-charge limited mechanism at low gate voltages. Vertical transport is required by three-dimensional integration technologies to increase the density of transistors on chip.

Training of deep neural networks (DNNs) is a computationally intensive task and requires massive volumes of data transfer. Performing these operations with the conventional von Neumann architectures creates unmanageable time and power costs. Recent studies have shown that mixed-signal designs involving resistive crossbar architectures are capable of achieving acceleration factors as high as 30 000 × over the state of the art digital processors. These approaches involve utilization of non-volatile memory elements as local processors. However, no technology has been developed to-date that can satisfy the strict device requirements for the unit cell. This paper presents the superconducting nanowire-based processing element as a crosspoint device. The unit cell has many programmable non-volatile states that can be used to perform analog multiplication. Importantly, these states are intrinsically discrete due to quantization of flux, which provides symmetric switching characteristics. Operation of these devices in a crossbar is described and verified with electro-thermal circuit simulations. Finally, validation of the concept in an actual DNN training task is shown using an emulator.

In this work, the first observation of the space charge limited conduction mechanism (SCLC) in GaAsSb nanowires (NWs) grown by Ga-assisted molecular beam epitaxial technique, and the effect of ultra-high vacuum in situ annealing have been investigated. The low onset voltage of the SCLC in the NW configuration has been advantageously exploited to extract trap density and trap distribution in the bandgap of this material system, using simple temperature dependent current–voltage measurements in both the ensemble and single nanowires. In situ annealing in ultra-high vacuum revealed significant reduction in the trap density from 10¹⁶ cm⁻³ in as-grown NWs to a low level of 7 × 10¹⁴ cm⁻³ and confining wider trap distribution to a single trap depth at 0.12 eV. A comparison of current conduction mechanism in the respective single nanowires using conductive atomic force microscopy (C-AFM) further confirms the SCLC mechanism identified in GaAsSb ensemble device to be intrinsic. Higher current observed in current mapping by C-AFM, increased 4 K photoluminescence (PL) intensity along with reduced full-width half maxima and more symmetric PL spectra, and reduced asymmetrical broadening with increased TO/LO mode in room temperature Raman spectra for in situ annealed NWs again attest to effective annihilation of traps leading to the improved optical quality of NWs compared to as-grown NWs. Hence, the I–V–T analysis of the SCLC mechanism has been demonstrated as a simple approach to obtain information on growth induced traps in the NWs.

Semiconducting metal oxide gas sensors typically operate at a high temperature and consume hundreds of milliwatts of power. Therefore there is great demand for the development of a low-power gas-sensing technology that can sensitively and selectively detect the gas analytes present in the atmosphere. We report an ultralow-power nanosensor array platform, integrated with an independently controlled nanoheater of size 4 μm × 100 nm, which consumes ∼1.8 mW power when operated continuously at 300 °C. The heaters exhibit a fast thermal response time of less than 1 μs, and can be utilized to operate in duty cycle mode, leading to power saving. The active area of the nanosensor is 1 μm × 200 nm, defined by sensing electrodes with a nanogap of ∼200nm, leading to small form factor. As a proof of concept, each of the sensing elements in the array is functionalized with different sensing materials to demonstrate a low-power, sensitive and selective multiplexed gas-sensing technology for the simultaneous detection of CO (∼93.2% for 3 ppm at 300 °C), CO₂ (∼76.3% for 1000 ppm at 265 °C), NO₂ (∼2301% for 3 ppm at 150 °C) and SO₂ (∼94% for 3 ppm at 265 °C). The technology described here uses scalable crossbar architecture for sensor elements, thus enabling the integration of additional sensing materials and making it customizable for specific applications.

Copper nanoparticles (NPs) are considered as a promising alternative for silver and gold NPs in conductive inks for the application of printing electronics, since copper shows a high electrical conductivity but is significantly cheaper than silver and gold. In this study, copper NPs were synthesized in the gas phase by transferred arc discharge, which has demonstrated scale-up potential. Depending on the production parameters, copper NPs can be continuously synthesized at a production rate of 1.2–5.5 g h⁻¹, while their Brunauer–Emmett–Teller sizes were maintained below 100 nm. To investigate the suitability in electronic printing, we use ball milling technique to produce copper conductive inks. The effect of ball milling parameters on ink stability was discussed. In addition, the electrical resistivity of copper films sintered at 300 °C in reducing atmosphere was measured to be 5.4 ± 0.6 μΩ cm which is about three times higher than that of bulk copper (1.7 μΩ cm). This indicates that conductive inks prepared from gas-phase synthesized copper NPs are competitive to the conductive inks prepared from chemically synthesized copper NPs.

The article reports on an optimization of gold submicron structures based on modified recordable blank digital versatile discs for surface plasmon polaritions excitation, mainly in near-infrared region. We have examined internal layers of commercially available DVD+R, DVD-R, DVD+RW and DVD-RW optical discs and we have elaborated a simple, inexpensive approach providing sharp resonances with efficiency reaching 95% for collimated excitation laser beams. We have experimentally and numerically confirmed the SPPs intensity being up to 220 times the intensity of the excitation laser beam. We have also directly measured thermal energy loss accompanying SPPs excitation.

Design and synthesis of Pt-based nanocrystals with controlled structural diversity and complexity can potentially bring about multifunctional properties. In this work, we present a facile two-step strategy for the construction of the PtPdRh mesoporous octahedral nanocages (PtPdRh MONCs). This unique nanoarchitectonics rationally integrates multiple advantages (i.e. the octahedral shape, hollow cavity and mesoporous surface) into one catalyst, which facilitates the efficient utilization of noble metal atoms at both of the interior and exterior surfaces. As expected, the resultant PtPdRh MONCs could effectively catalyze the oxygen reduction reaction (ORR) under acidic conditions. The demonstrated ORR activity and catalytic durability are superior to the commercial Pt/C catalyst. The present study would provide a general guidance for architectural and compositional engineering of noble metal nanocrystals with desired functionalities and properties.

Flexible, heteroatoms-rich activated carbon nanofibers with fascinating cross-linked architectures are successfully gained in a facile and controllable way via electrospinning polyacrylonitrile (PAN) /dicyandiamide (DICY) composite nanofibers followed by carbonation and a CO₂ activation process. The unique inter-bonded structures and heteroatoms contents could be easily controlled by adjusting the preoxidation temperature applied in the calcining procedure and the addition of DICY. Significantly, the resultant samples display hierarchical pores with micro/meso/macropores, abundant N, O species doped and unique fiber–fiber interconnections, which considerably boost the electrochemical properties. As an electrode material, the activated N-doped cross-linked carbon nanofibers (ANCLCNFs) show a high capacitance of 323 F g⁻¹ with a current density of 0.5 A g⁻¹, excellent rate capacity (230.1 F g⁻¹ at 20 A g⁻¹) and long-term duration (over 95% after 10000 cycles). Furthermore, the symmetrical supercapacitor delivers a maximum energy density of 14.3 Wh kg⁻¹ at a power density of 162.5 W kg⁻¹.

Lithium-sulfur (Li/S) batteries are promising portable energy storage devices if the defects of insufficient conductivity and obvious shuttle effect can be effectively suppressed. In this work, a unique caddice-like ball carbon nanotubes/CoO (CNTs/CoO) microspheres have been synthesized through a facile spray drying and following calcination method. By using cobalt acetate (Co(CHCOO)₂) as a cobalt source, polymethyl methacrylate (PMMA) as a pore former and CNTs as the supporting frame, the as-prepared CNTs/CoO microspheres endowed with enriched interconnected pores and abundant scattered CoO nanoparticles on CNT walls. CNTs provided physical adsorption platforms for adsorption of polysulfides while ensuring the conductivity of the overall material. Polycrystalline CoO nanoparticles are uniformly deposited on CNT walls, providing additional confinement of polysulfides by strong chemical adsorption. In addition, the different content of CoO in the microspheres was regulated by the amount of added cobalt source during the preparation process. With both physical entrapment by CNTs and strong chemical interaction with CoO nanocrystals, this unique design can effectively promote the active material utilization and inhibit the shuttle effect. When employed as the sulfur host, an excellent electrochemical performance was achieved on the resulting sulfur-impregnated CNTs/CoO (S-CNTs/CoO) composite with the sulfur content of 73.0%. The obtained S-CNTs/CoO microspheres delivered an exceptional initial discharge capacity of 1340 mAh g⁻¹ and a prominent cycling stability of 1116 mAh g⁻¹ after 100 cycles at 0.2 C, as well as a superb rate capability of 600 mAh g⁻¹ and 506 mAh g⁻¹ at 2.0 C and 3.0 C, respectively. The results revealed that the S-CNTs/CoO composite was an enviable cathode material and showed an excellent potentiality in the application of Li/S batteries.

In this study, a novel photocatalyst composed of N-doped TiO₂ (N-TiO₂) and (Ca, Y)F₂:Yb³⁺, Tm³⁺ was prepared by simple dealloying followed by a hydrothermal method. The composite exhibits a homogeneous nanoporous structure consisting of large quantities of the spindle-like N-doped TiO₂ nanorods, on which the (Ca, Y)F₂:Yb³⁺, Tm³⁺ particles with a diameter of around 5 nm are uniformly dispersed. In addition, morphology and property of the N-TiO₂ can be controlled by adjusting the dealloying period. Results show that a short immersion time leads to a small size, large surface area and low band gap. As a result, the N-TiO₂/(Ca, Y)F₂:Yb³⁺, Tm³⁺ composite after dealloying for 48 h (TiO₂-48-C) exhibits higher degradation rates (65.6% for 10 h irradiation by 980 nm NIR) than others after dealloying for 60 h (TiO₂-60-C) and 72 h (TiO₂-72-C), indicating its excellent potential for practical applications.

Fabrication of practical devices based on the transient metal dichalcogenides (TMDs) can be successively extended to various areas of the applications if the large area growth technology can be intentionally controlled and the characteristics of the layers can be easily predicted. In present work we presented the principles of the technology control based on the single key variable that can be directly related to the sequence of the technological processes. The atomically thin MoS₂ layers were used as a model material and the layers were obtained by the CVD synthesis of the molybdenum precursor. Our thorough study demonstrated that the method allowed to deliberately choose the number of the MoS₂ two-dimensional (2D)-layers between 1 and 10 by simply choosing the precursor deposition time. The optical properties of the layers were characterised by the optical transitions that corresponded to the known band structure of the MoS₂ layers. Fused calibration diagram was proposed as the practical tool for the technology control and it was proved to be highly successive in relating the 2D-properties of the films with the initial stage of the fabrication technology. The method can be adapted to the wafer size TMDs growth on the diverse substrates.

Nanotubes are prone to collapsing under compression due to the competition between the bending stiffness of the walls and the van der Waals interactions. The different radial morphologies during collapse may affect the electrical properties of nanotube, which may find promising potential applications in strain engineering. In this paper, the finite-deformation model is introduced to determine the radial morphologies, energy barrier and radial deformability of a nanotube under compression, in which the adhesion interactions are analytically obtained. The analytical solutions of the radial morphologies during compression are consistent with the molecular dynamics simulations results, indicating the effectiveness of the finite-deformation model. The analytical results reveal that both the energy barrier and the radial deformability show a decreasing tendency with the increase of the nanotube diameter.

Bottom-up constructions of hierarchical TiO₂ are effective to enhance their photoactivity towards degradations of organic pollutants. Thanks to highly active facets, {001} exposed anatase TiO₂ microcrystals attract much attention in photocatalysis; yet their efficiency is limited by the large crystal size. Herein, we report a facile solution approach to deposit anatase TiO₂ mesocrystals only on {101} facets of anatase TiO₂ microcrystals. The selective surface decoration enhances the photoactivity through replacing the less active {101} facets with more active TiO₂ mesocrystals; whilst the highly active {001} facets remain untouched. When utilized to assist photodegradation of phenol in water under UV light illumination, the hierarchical TiO₂ exhibited a reaction rate constant doubled that of the pristine {001} exposed TiO₂ microcrystals. The present tactic to selectively decorate TiO₂ microcrystals may give hints to other applications involving facet-dependent properties.

In the present work, a fluorescent gold nanoclusters (GNCs)/superparamagnetic (Fe₃O₄/GNCs) nanoprobe was prepared via a facile approach for the selective detection and imaging of human leukemica cancer cells (HL-60). (γ-Mercaptopropyl)trimethoxysilane (MPS) was used as a stabilizer to prepare functionalized GNCs. The prepared GNCs@MPS was then self-assembly decorated on the surface of Fe₃O₄@SiO₂ nanoparticles followed by poly(ethylene glycol) dimethacrylate (PGD) addition at room temperature to form Fe₃O₄/GNCs nanoprobe. Surface functionalization of the Fe₃O₄/GNCs with the thiol-modified KH1C12 aptamer was done through thiol-en click reaction between PGD and the thiol group of the aptamer. An extensive characterization of the Fe₃O₄/GNCs revealed strong red fluorescence (λ_em = 627 nm), T₂-based contrast agent for MRI and excellent colloidal and photo stability in buffer medium. So, the aptamer-functionalized Fe₃O₄/GNCs nanoprobe (Fe₃O₄/GNCs/Aptamer) is capable to uptake and dual-image HL-60 cancer cells from a mixture. Furthermore, the MRI signal intensity of the pictures decreased linearly with an increase in the concentrations of the nanoprobe. It is also enable to detect cancer cells from a range of concentrations 10 up to 200 cells μL⁻¹. The fluorescent/magnetic characteristics of the nanoprobe are of great significance for MRI-based and fluorescence imaging and collection of HL-60 cancer cells which implies potential help for the development of early diagnosis of highly malignant human leukemia.

We study the topological properties of finite-size S-shaped graphene junctions with distinctive edge features subjected to the perpendicular magnetic field, using the tight-binding model. The quantum confinement and edge effects induced by the specific junction give rise to significant modifications in the Hofstadter spectra of the bent flakes, when compared to those of their perfect forms. Moreover, the results show that in absence of a magnetic field, the sharpest zigzag-edged corners support the edge states rather than the others, but the magnetic field leads to the localization of the edge states along the whole perimeter of the flakes. Furthermore, based on the Green's function method, we investigate the electron transport through our proposed junctions. We show that, under magnetic flux, one can effectively control the energy gap and the conductance around the Fermi energy. Moreover, the transitions between metallic, semimetallic, and semiconducting phases are possible by the magnetic flux in the S-shaped junctions.

The sensitivity of circularly polarized x-ray resonant magnetic scattering (CXRMS) to chiral asymmetry has been demonstrated. The study was performed on a 2D array of Permalloy (Py) square nanomagnets of 700 nm lateral size arranged in a chess pattern, in a square lattice of 1000 nm lattice parameter. Previous x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM) images on this sample showed the formation of vortices at remanence and a preference in their chiral state. The magnetic hysteresis loops of the array along the diagonal axis of the squares indicate a non-negligible and anisotropic interaction between vortices. The intensity of the magnetic scattering using circularly polarized light along one of the diagonal axes of the square magnets becomes asymmetric in intensity in the direction transversal to the incident plane at fields where the vortex states are formed. The asymmetry sign is inverted when the direction of the applied magnetic field is inverted. The result is the expected in the presence of an unbalanced chiral distribution. The effect is observed by CXRMS due to the interference between the charge scattering and the magnetic scattering.

We have investigated the response of the high entropy alloy of CoNiCrFeMn to the bombardment under extreme irradiation flux by means of molecular dynamics simulations. Compared to pristine Ni single crystalline, the CoNiCrFeMn HEA had less point defects during a single primary knock-on atom process. The average depth of defects was shallower. For consecutive bombardments, the CoNiCrFeMn HEA demonstrated much higher surface irradiation resistance than pristine Ni. Under the irradiation flux of 5.59 × 10²⁷ n/(m^2*s), the number of defects in Ni gradually increased and was proportional to the number of bombardments, till the formation of dislocation which led to a boost of the defects. On the contrary, the number of defects in CoNiCrFeMn HEA was much less and stable, appearing to be insensitive to the number of bombardments and suggesting good radiation resistance. Such radiation resistance of CoNiCrFeMn HEA was attributed to the lattice distortion and sluggish diffusion of atoms, which could enhance the recombination of defects. Under the irradiation flux of 1.68 × 10²⁸ n/(m^2*s), the boost of the defects in Ni occurred at lower number of bombardments. In addition, under both the irradiation flux of 5.59 × 10²⁷ and 1.68 × 10²⁸ n/(m^2*s), CoNiCrFeMn HEA had a smaller number of point defects and the defects were well dispersed. Our results showed that compared with Ni matrix, CoNiCrFeMn HEA had higher surface bombardment tolerance. This study might be helpful in the design of first-wall materials under the extreme irradiation flux.

Self-healing polymer materials (SHPM) have aroused great interests in recent years. Ideal SHPM should have not only simple operations, but also high elongations at break, tensile strain and self-healing properties at room temperature. Herein, the amidated carbon fibers (CFs) reinforced self-healing polymer composites were designed by hydrogen bonding interaction between functionalized CFs and hyperbranched polymers. The amidated CFs were prepared by transformation of hydroxyl to acylamino through a one-step amidation. By introducing amidated CFs, amidated CFs self-healing polymer composites (called AD-CF) exhibited many desirable characteristics compared to pure polymer composites, such as a better elasticity, lower healing temperatures, and higher self-healing efficiencies. The stress–strain test was selected to carefully study the self-healing property of the AD-CF. The observed same recovery condition, i.e. without any mechanical breakdown after the 10 sequential cycles of cutting and healing indicates no aging of the AD-CF. The ability of AD-CF to exhibit a soft state and rapid self-healing at room temperature makes it possible for much wider applications.

Zinc oxide (ZnO) one-dimensional nanostructures are extensively used in ultra-violet (UV) detection. To improve the optical sensing capability of ZnO, various nickel oxide (NiO) based p–n junctions have been employed. ZnO/NiO heterojunction based sensing has been limited to UV detection and not been extended to the visible region. In the present work, p-NiO/n-ZnO composite nanowire (NW) heterojunction based UV-visible photodetector is fabricated. A porous anodic aluminum oxide template based electrochemical deposition method is adopted for well separated and vertically aligned growth of composite NWs. The photoresponse is studied in an out of plane contact configuration. The fabricated photodetector shows fast response under UV-visible light with a rise and decay time of tens of ms. The wide spectral photoresponse is analyzed in terms of conduction from defect states of ZnO and interfacial defects during p–n junction formation. Light interaction with heterojunction along the length of the composite NW results in enhanced visible photoresponse of the detector and is further supported by simulation.

InSb/InAs sub-monolayer (SML) nanostructures such as SML quantum dots offer sharper emission spectra, a better modal gain and a larger modulation bandwidth compared to its Stranski–Krastanov counterpart. In this work, the Sb distribution of SML InSb layers grown by migration enhanced epitaxy has been analyzed by transmission electron microscopy (TEM) techniques. The analysis of the material by diffraction contrast in 002 dark field conditions and by atomic column resolved high angle annular dark field-scanning TEM reveal the presence of a low Sb content InSbAs continuous layer with scarce Sb-rich InSbAs agglomerates. The intensity profiles obtained by both techniques point to Sb segregation during growth. This segregation has been quantified using the Muraki segregation model obtaining a high segregation coefficient R of 0.81 towards the growth direction. The formation of a continuous InSbAs wetting layer as a result of a SML deposition of Sb on the InAs surface is discussed.

Over the last two decades, iron oxide based nanoparticles ferrofluids have attracted significant attention for a wide range of applications. For the successful use of these materials in biotechnology and energy, surface coating and specific functionalization is critical to achieve high dispersibility and colloidal stability of the nanoparticles in the ferrofluids. In view of this, the magnetic behavior of clusters of ultra-small MnFe₂O₄ nanoparticles covered by bovine serum albumin, which is known as a highly biocompatible and environmentally friendly surfactant, is investigated by magnetization measurements, and numerical simulations at an atomic and mesoscopic scale. The coating process with albumin produces a change in the structure, actual size and shape distribution of clusters of exchange coupled particles, giving rise to a distribution of blocking temperatures. The coated system exhibits a superspin glass (SSG) behavior with the SSG freezing temperatures similar to the uncoated ones, providing evidence that the strength of the dipolar interactions is not affected by the presence of the albumin. The DFT calculations show that the albumin coating reduces the surface anisotropy and the saturation magnetization in the nanoparticles leading to lower values of the coercive field in agreement with the experimental findings. Our results clearly demonstrate that the albumin coated clusters of MnFe₂O₄ particles are ideal systems for energy and biomedical applications since colloidal and thermal stability as well as biosafety is obtained through the albumin coating.

In this paper, we present high-performance and versatile inkjet-printed paper photo-actuators based on two-dimensional (2D) nanomaterials. As a rapid fabrication method, inkjet printing of 2D materials is used to promptly fabricate photo-actuators in a bi-layer paper/polymer structure. Water-based and biocompatible inks based on graphene and molybdenum disulfide are developed based on liquid phase exfoliation and differential centrifugation technique. It is shown that incorporation of 2D materials with inkjet printing techniques and liquid phase exfoliation can lead to rapid fabrication of photo-actuators with huge opto-mechanical energy release and versatility with a broad range of applications due to specific design and methods presented in this paper.

Helical graphene nanoribbons (HGNRs) are a special structure made of single-layer graphene, which are of interest in the nanotechnology because of their unique mechanical features. Here we propose an asymmetrical nonlinear spring model (ANSM) for designing different HGNRs used in the dynamic nano-indentation testing. Both nonlinear static and dynamics behaviors of HGNRs are studied using molecular dynamics (MD) simulations and the ANSM, respectively. The interlayer van der Waals interactions, which play a key role in the mechanical behaviors of HGNRs, are quantitatively considered in the ANSM with quadratic and cubic nonlinearities. The response-frequency curves of forced vibrations in HGNRs show clear softening-type nonlinearity. In particular, a remarkable transformation from softening-type to hardening-type nonlinearity occurs with increasing contact stiffness in nonlinear dynamics behaviors of HGNRs. Checking against present static and linear dynamics results of MD simulations shows that the ANSM has high accuracy. The present study provides valuable physical insights for designing and assembling HGNR-based resonators.

Electronic properties of graphene/ZnO interface have been theoretically investigated by applying first principles density functional theory calculations. This interface is demonstrated to have interesting electrical, optical and chemical properties and therefore, is employed in different applications. In our investigation the interface between graphene and different ZnO surfaces such as polar Zn-terminated $\left(0001\right)$ and O-terminated $\left(000\bar{1}\right)$ surfaces as well as nonpolar $(10\bar{1}0)$ surface are considered. Different interface properties such as equilibrium atomic structure, binding energy, charge transfer and band alignment are calculated for these interfaces. The calculated binding energies between graphene and different ZnO surfaces are within the range of van der Waals or physical adsorption. The results clearly reveal the essential role of oxygen density at the interface. The O- and Zn-terminated ZnO surfaces show the lowest and highest binding energies, respectively. The amount of charge transfer and the direction of interfacial dipole are also dominated by the number of oxygen atoms at the graphene/ZnO interface. Calculations for the interfacial band alignment reveal that a high/low density of oxygen atoms at the interface results in a Schottky/Ohmic contact. It is also shown that inducing oxygen vacancies at an oxygen rich interface leads to the lowering of the Schottky barrier.

Introducing disorder into a periodic nanostructure can lead to specific optical behaviors. We present a method of anodic oxidation by adjusting the applied voltage and process time to introduce disorder to TiO₂ nanotubes. The surface morphology of TiO₂ was numerically investigated according to the morphologies measured with a scanning electron microscope by imaging processing and a statistical method. TiO₂ nanotubes obtained under different fabrication conditions have various tube radii ranging from 20–40 nm and wall thicknesses ranging from 20–70 nm. We also evaluated the degree of disorder of the tube radius of the TiO₂ nanotubes. The reflected scattering light distributions of laser sources were optically measured at different observing distances, which indicate that the presence of nanotubes enhances the scattering effect, reducing the scattered light intensity by more than 75%, and provide the relationship between the scattering effect and surface morphology of nanotubes. This discovery offers TiO₂ nanotubes important application prospects in optical limiting and light confinement, such as stealth coating.