Nano silicon structures are important materials for modern electronic devices and have been widely researched with regard to photoelectricity, thermoelectricity, and lithium-ion batteries. However, since the nano silicon structures fabricated by conventional methods cannot be separated from silicon substrates, reuse of the substrate is restricted. Here, we propose a simple fabrication method to separate the nano silicon structures from the silicon substrates, which allows the reuse of the substrates. The fabrication was processed at room temperature, which allows large-area fabrication and is not restricted by the substrate thickness. Honeycomb structures of different length scales observed on both the nano silicon structure and the substrate suggest that the separation occurred due to the amplification of the silicon crystal defects. The nano silicon structures comprised porous silicon with an excellent specific surface area of 480 m2 g−1 and a mean pore diameter of 5.7 nm. Moreover, the nano silicon structures show good potential as anode materials for lithium-ion batteries wherein the measured reversible capacity was 1,966 mAh g−1 after 100 cycles. Based on the proposed method and morphological characteristics, the fabricated nano silicon structures can be considered a low-cost material with suitable applications in the energy field.

Surface plasmon are widely used to promote the exciton generation and light absorption in solar cells and photodetectors. In this work, a feasible approach for UV–vis-NIR photodetection using plasmon-enhanced silicon nanowires (SiNWs) and amorphous TiO2 heterostructure is presented. The photodetector shows excellent photo response up to 3.3 orders of magnitude enhancement with rise/decay times of 77/51 μs. Under small external bias (1V), the photodetector exhibits very high responsivity up to 49 A W−1 over a broadband wavelength range from 300–1100 nm. All the experimental procedures are performed at room temperature in ambient conditions. Its simple fabrication route and excellent performance make this photodetector distinct from similar architectures. Our finding offers new opportunities to engineer plasmon-based nanostructures in chemical sensors, optoelectronics and nanophotonic devices and applications.

Meta-atoms interact with light in interesting ways and offer a large range of exciting properties. They exhibit optical properties inaccessible by natural atoms but their fabrication is notoriously difficult because of the precision required. In this perspective, we present the current research landscape in making meta-atoms, with a focus on the most promising self-assembly approaches and main challenges to overcome, for the development of materials with novel properties at optical frequencies.

One promising way to reduce the use of noble metal catalysts is to use extremely fine particle catalysts, such as subnanoclusters and single-atom catalysts. For practical use, suppression of diffusion and agglomeration of catalysts are needed. Heteroatom-doped graphene, which has high specific surface area, high chemical and mechanical stabilities, high electrical and thermal conductivities, and contains anchoring sites for catalysts, is promising catalyst support. Heteroatom-doped graphene can widely control the support effects. This review summarizes recent dopant structure characterization using spectroscopy and density functional theory calculations. The distribution of highly-dispersed metal catalysts and their diffusion properties are discussed. In addition, The effects of environmental conditions on catalyst dynamic behaviors are introduced. Finally, the outlook of heteroatom-doped graphene and new two-dimensional material supports is discussed.

TiO2 thin films with an inverse opal-like structure have attracted considerable attention recently owing to their high potential for a range of applications. In this study, we demonstrated the possibility to deposit TiO2 thin films with an inverse opal-like structure from TiO2 nanoparticle-based slurry paste using a conventional spin-coating process. In addition, we also showed that the photoelectrochemical (PEC) performance of as-fabricated inverse opal-like TiO2 films can be further improved by the dip-coating process. In particular, dip-coated and untreated inverse opal-like TiO2 films exhibit photocurrent densities of ∼66.5 μA cm−2 and ∼40.9 μA cm−2 at 1.23 V versus RHE, respectively. A detailed physicochemical analysis revealed that photocurrent density enhancement (∼38.5%) in dip-coated inverse opal-like films can be attributed to a variety of factors including improved interconnection between TiO2 nanoparticles, higher crystallinity, decreased light reflection, and reduced charge carriers recombination. We strongly believe that these findings will be useful in the development of highly efficient third-generation solar cells, photocatalytic systems, electrochromic devices, and gas sensors.

This study considers the dependence of the force caused by the dipolar interaction between small low-dimensional magnets such as single-molecule magnets and two-dimensional magnets on the distance between them within the framework of the dipolar Ising model with nearest-neighbor exchange interactions and long-range dipolar interactions. In particular, we focus on the rapid change in the force between ferromagnetic and antiferromagnetic plates, which arise from the transition of the spin states and explain that this behavior originates from the spin frustrations between magnetic plates. Furthermore, the size and temperature dependence of the interaction energy are investigated using a Monte Carlo simulation.

Because chemical reactions are largely governed by the movement of electrons, it is possible to control chemical reactions using electronic devices that provide functionality by controlling the movement of electrons in a solid. In this perspective, we discuss the concept of ‘field-effect surface chemistry,’ which controls chemical reactions on two-dimensional materials using field-effect transistors (FETs), a representative electronic device. The electrical voltages to be applied for the FET operation are the gate voltage and drain voltage. The former is expected to control the Fermi level and exert the effect of the electric field directly on the reactants, while the latter is expected to provide local heating by Joule heat and energy transfer to the reactants. Further, we discuss a sample structure that does not require any voltage but has the same effect as the gate voltage.

Presently carbon allotropes namely graphene, graphene oxide (GO) and reduced graphene oxide (RGO) are being extensively utilized for water purification applications. The presence of myriad types of oxygen functional groups in the GO, however, makes this material very hydrophilic, allowing it to absorb water and to swell in moist or watery environments and to significantly damage its intended performance. In contrast, fully reduced graphene oxide membranes are not stable due to fewer oxide groups which are mainly responsible for GO flakes stacking. In the present work, the aforementioned problems are overcome by optimizing the oxygenated functional groups to develop mildly reduced graphene oxide (MRGO) membrane over PVDF (polyvinylidene fluoride) support. GO is reduced by L-Ascorbic Acid (LAA) with different amounts of wt.% and an optimized MRGO membrane is achieved at 10 wt.% of LAA, which is stable and showing comparatively lower swelling than GO membrane. All related structural and optical characterizations like XRD, SEM, EDAX, Raman, FTIR, and Contact angle have been done to evaluate the effect of mild reduction of GO. The studies are indicative of their potential application in water purification.

Ammonium wastewater is a serious and common water pollutant that can have harmful effects on the environment. Freeze concentration, as an energy-efficient and environmentally friendly method, is used to treat ammonium wastewater by ice-water phase transition. The simulation results show that most of the ions are retained in the liquidphase, and it is reported for the first time that the probability of NH4 + (90%) remaining in the water is significantly higher than that of Cl− (67%). We have analyzed the influence of ions on ice/water structure from the perspective of structure and energy and explained the reason for the difference in the probability of NH4 + and Cl− remaining in the liquid phase. We find that the coordination number (CN) of NH4 + decreases from 6 to 4 when one NH4 + permeates the ice layer, indicating that the first hydration layer of ammonium ions underwent significant reorganization during this period. In contrast, a similar reduction in CN was not observed during the entry of Cl− into the ice layer. Moreover, the hydration energy shows that NH4 + prefers to stay in the liquid phase than in the ice phase because of the higher hydration energy difference compared with that of Cl−. The results of this work indicate that freeze concentration can efficiently remove NH4 + by ice-water phase transition, which greatly reduces the discharge of ammonium wastewater and pave the way for further study of the freezing process for wastewater treatment.

Carrier doping is an essential way to inject holes and electrons to electronic materials, which modulates their transport properties. While the substitution of heteroatoms essentially modulates the band structure of most semiconducting materials, chemical (molecular) doping can achieve relatively reliable carrier concentration modulation, particularly for nanocarbons and two-dimensional semiconductors. Compared to p-type counterparts, the stabilization of n-type carbon materials has been a challenge not only for basic science but also for various electronic device applications. This Mini-Review describes rational concepts for, and the results of, a stable n-type doping technique mainly for carbon nanotubes using molecular reactions and interactions. The stable n-type carbon nanotubes with controlled carrier concentration are implemented in complementary circuits and thermoelectric energy harvesters. The molecular and supramolecular n-type doping is not limited for carbon nanotubes, but is utilized in the fabrication of conducting transition metal dichalcogenides such as a molybdenum disulphide (MoS2) monolayer.

We report on the potential use of the intrinsic ferromagnetic rare earth nitride (REN) semiconductors as ferromagnetic electrodes in tunnelling magnetoresistance and giant magnetoresistance device structures for non-volatile memory storage devices. Non-volatile memory elements utilising magnetic materials have been an industry standard for decades. However, the typical metallic ferromagnets and dilute magnetic semiconductors used lack the ability to independently tune the magnetic and electronic properties. In this regard, the rare earth nitride series offer an ultimately tuneable group of materials. Here we have fabricated two tri-layer structures using intrinsically ferromagnetic rare earth nitride semiconductors as the ferromagnetic layers. We have demonstrated both a non-volatile magnetic tunnel junction (MTJ) and an in-plane conduction device using GdN and DyN as the ferromagnetic layers, with a maximum difference in resistive states of ∼1.2% at zero-field. GdN and DyN layers were shown to be sufficiently decoupled and individual magnetic transitions were observed for each ferromagnetic layer.

Hot-electron photodetectors (HE PDs) are attracting a great deal of attention from plasmonic community. Many efficient HE PDs with various plasmonic nanostructures have been demonstrated, but their preparations usually rely on complicated and costly fabrication techniques. Planar HE PDs are viewed as potential candidates of cost-effective and large-area applications, but they likely fail in the simultaneous achievement of outstanding optical absorption and hot-electron collection. To reconcile the contradiction between optical and electrical requirements, herein, we propose a planar HE PD based on optical Tamm plasmons (TPs) consisted of an ultrathin gold film (10 nm) sandwiched between two distributed Bragg reflectors (DBRs). Simulated results show that strong optical absorption (>0.95) in the ultrathin Au film is realized. Electrical calculations show that the predicted peak photo-responsivity of proposed HE PD with double DBRs is over two times larger than that of conventional single-DBR HE PD. Moreover, the planar dual-DBR HE PDs exhibit a narrowband photodetection functionality and sustained performance under oblique incidences. The optical nature associated with TP resonance is elaborated.

Stable silver clusters can be prepared by a simple electroless reduction reaction taking place in water-in-oil emulsions. An emulsion containing AgNO3 in the water droplets was mixed with a similar emulsion containing aqueous NaBH4 droplets. The droplet diameter, based on Rayleigh scattering, was 41 nm and the mean number of Ag+ ions in each droplet varied from 2.0 to 21.7 as the concentration increased from 90 μM to 1 mM AgNO3. The low number of Ag+ ions in each droplet inhibits the growth of large nanoparticles and these emulsions do not show the large plasmon band observed for Ag nanoparticles obtained by the analogous reaction in bulk solution at the same Ag+ concentrations. Atomic force microscopy provides evidence of small Ag nanoclusters and a much lower number of larger nanoparticles. Electrospray mass spectrometry suggests that the clusters are mainly Ag4 species coordinated to water and BH4 −. The Ag nanocluster-containing emulsions are fluorescent and show an emission band with a peak wavelength of 427 nm and a Stokes shift of 81 nm from the first peak at 346 nm in the excitation spectrum. The intensity of fluorescence decreased as the [Ag(I)] increased and our most fluorescent samples were prepared from 90 μM AgNO3 because at higher concentrations more Ag nanoparticles are formed. DFT calculations on Agn clusters indicated that Ag4 species favour a planar rhombic geometry even in the presence of coordinating water molecules or BH4 −. However calculations of vertical excitation energies for Ag4 species do not match the experimental excitation spectra and this suggests the fluorescence arises from bright AgNCs of different nuclearity present at lower abundance in the mixture of species produced by the emulsion reaction. Calculated excitation energies for Ag6 give the best fit to the available data.

In the present study, the heat generation in gold nanodimer when irradiated at their localized surface plasmon resonances is investigated numerically. The theoretical calculations are performed employing the first principal approach to obtain the absorption cross-section of gold nanodimer for different parameter ranges. The heating mechanism is enumerated in terms of its temperature by solving the steady-state heat transfer equation which depends on the absorption cross-section and surface plasmon resonance wavelength. These surface plasmon resonances are quite sensitive to the distance between the dimer and have been tuned from visible to IR range by managing the distance between spheres from 0 to 6 nm. The computation of normalized electric field distribution of gold nanodimer under the plasmon resonance has been mapped using boundary element method(BEM) which enables visualization of the local hot spot that plays a significant role in optical heating applications. The work furnishes the basic understanding of the heating mechanism of gold nanodimer which can find application as plasmonic nanoheaters in several branches of science in visible and near-infrared regions of the electromagnetic spectrum.

In this study we are presenting the synthesis of MnO2 nanorods using hydrothermal method assisted by facile tri-ethanolamine-ethoxylate. Structural (x-ray diffraction, Rietveld refinement), functional (Fourier Transform Infrared spectroscopy and x-ray Photoelectron Spectroscopy) and morphological (Field emission scanning electron microscope, Transmission electron microscopy) characterization conform the β-MnO2 nanostructure with a rod-like morphology and uniform thickness. The morphological variations of the nanorod thickness can be easily controlled by simply monitoring the reaction temperature. Comparative investigations of β-MnO2 samples synthesized at two different reaction temperatures (viz. 100 C and 120 C) used as a supercapacitive electrode material have been performed with the aid of different electrochemical techniques. With different electrolytes (Li2SO4 and Na2SO4), supercapacitor device is tested using Cyclic voltammetry, impedance spectroscopy and galvanostatic charge discharge. Interestingly, the low temperature synthesized β-MnO2 nanorods sample exhibit superior electrochemical performance in 1 mol l−1 Li2SO4 electrolyte in terms of high specific capacitance (462 Fg−1 at10 mVs−1), energy density (9.72 WhKg−1), and outstanding cyclic stability (90.26% over 2000 cycles).

Graphene has received much attention in multiple fields due to its unique physical and electrical properties, especially in the microelectronic application. Nowadays, graphene can be catalytically produced on active substrates by chemical vapor deposition and then transferred to the target substrates. However, the widely used wet transfer technique often causes inevitable structural damage and surface contamination to the synthetic CVD graphene, thus hindering its application in high-performance devices. There have been numerous reviews on graphene growth and transfer techniques. Thus, this review is not intended to be comprehensive; instead, we focus on the advanced plasma treatment, which may play an important role in the quality improvement throughout the growth and transfer of graphene. Promising pathways for future applications are also provided.

Due to their innovative functions, the use of nanoparticles in various industries has been expanding. However, a key concern is whether nanoparticles induce unexpected biological effects. Although many studies have focused on innate immunity, information on whether nanoparticles induce biological responses through effects on acquired immunity is sparse. Here, to assess the effects of amorphous silica nanoparticles on acquired immunity, we analyzed changes in acute toxicities after pretreatment with amorphous silica nanoparticles (50 nm in diameter; nSP50). Pretreatment with nSP50 biochemically and pathologically exacerbated nSP50-induced hepatic damage in immunocompetent mice, while pretreatment with nSP50 did not exacerbate hepatic damage in immunodeficient mice. Consistent with this, the depletion of CD8+ cells with an anti-CD8 antibody in animals pretreated with nSP50 resulted in lower plasma levels of hepatic injury markers such as ALT and AST after an intravenous administration than treatment with an isotype-matched control antibody. Finally, stimulation of splenocytes promoted the release of IFN-γ in nSP50-pretreated mice regardless of the stimulator used. Moreover, the blockade of IFN-γ decreased plasma levels of ALT and AST levels in nSP50-pretreated mice. Collectively, these data show that nSP50-induced acquired immunity leads to exacerbation of hepatic damage through the activation of cytotoxic T lymphocytes.

The aim of the present research is to understand the bouncing dynamic behavior of nanoelectromechanical (NEM) switches in order to improve switch performance and reliability. It is well known that bouncing can dramatically degrade the switch performance and life; hence, in the present study, the bouncing dynamics of a cantilever-based NEM switch has been studied in detail. To this end, the repulsive van der Waals force is incorporated into a nano-switch model to capture the contact dynamics. Intermolecular forces, surface effects, and gas rarefication effects were also included in the proposed model. The Euler–Bernoulli beam theory and an approximate approach based on Galerkin’s method have been employed to predict transient dynamic responses. In the present study, performance parameters such as initial contact time, permanent contact time, major bounce height, and the number of bounces, were quantified in the presence of interactive system nonlinearities. The performance parameters were used to investigate the influence of surface effects and rarefication effects on the performance of an electrostatically actuated switch. Recommended operating conditions are suggested to avoid excessive bouncing for these types of NEM switches.

Gold nanoparticles (GNPs) have served as an excellent candidate for biomedical applications. GNPs can be conjugated with carboxyl-polyethylene glycol-thiol (PEG) as a stealth coating which prolongs circulation time [Lipka J et al 2010 Biodistribution of PEG-modified gold nanoparticles following intratracheal instillation and intravenous injection. Biomaterials, 31 , 6574–6581, Janát-Amsbury M et al 2011 Geometry and surface characteristics of gold nanoparticles influence their biodistribution and uptake by macrophages. Eur. J. Pharm. Biopharm, 77 , 417–423] and increases cellular uptake.[He B et al 2017 Increased cellular uptake of peptide-modified PEGylated gold nanoparticles. Biochem. Biophys. Res. Commun., 494 , 339–345, Soenen S. J et al 2014 , The cellular interactions of PEGylated gold nanoparticles: effect of PEGylation on cellular uptake and cytotoxicity. Part. Part. Syst. Charact., 31 , 794–800, Guo J et al 2016 Bioconjugated gold nanoparticles enhance cellular uptake: A proof of concept study for siRNA delivery in prostate cancer cells. Int. J. Pharm., 509 , 16–27. Brandenberger C et al 2010 Quantitative evaluation of cellular uptake and trafficking of plain and polyethylene glycol‐coated gold nanoparticles. Small, 6 , 1669–1678. To examine the biological effects of PEG-coated GNPs, we investigated their cytotoxicity on human cervical cancer C33A cells as compared to citrate-capped GNPs. Our results indicated that PEGylated GNPs markedly induce apoptosis and necrosis causing cell shrinkage and cell membrane asymmetry. 30 nm citrate-capped GNPs were synthesized in aqueous solution using a citrate-reduction method. GNPs were functionalized with PEG (MW = 7500 g mol−1. The GNPs were characterized using scanning electron microscopy (SEM), confirming that the as-synthesized GNPs have a diameter of 30 nm. Dynamic light scattering (DLS) determined that the hydrodynamic diameter of PEGylated GNPs was 78.82 nm, and that of citrate-capped GNPs was 43.82 nm. Zeta potential measurements showed an increase in colloidal stability for PEGylated GNPs as compared to citrate GNPs, with a zeta potential of −33.33 mV observed for citrate-capped GNPs and a zeta potential of −43.38 mV observed for PEGylated GNPs. The PEGylated GNPs were found to effectively induce early and late-stage apoptosis in C33A cells with a significant reduction in total cell viability of 32.3%. Based on the apoptotic activity in C33A cells, PEGylated GNPs may serve as a promising radiosensitizer for cancer treatments.

Super paramagnetic iron oxide nanoparticles (SPIONs) (∼12 nm) were synthesized as the magnetic core for an imprinted polymer (MIP) shell using 4-vinylpyridine as the functional monomer and trimethylolpropane trimethacrylate (TRIM) as the cross-linker, bringing the average size up to ∼45 nm. Five targets were imprinted—the Selective Androgen Receptor Modulators (SARMs) andarine, ligandrol and RAD-140; and the steroids estradiol and gestrinone. All MMIPs produced good selectivity when loaded with a non-target molecule, with all calculated selectivity factors above the 1.2 recommended threshold and also demonstrated good affinity/capacity. The rebinding of the target molecules from a complex matrix was also explored by using spiked river water samples. The SARMs-based MMIPs were able to rebind 99.56, 87.63 and 72.78% of their target molecules (andarine, ligandrol and RAD-140, respectively), while the steroidal-based MMIPs were able to rebind 64.54 and 55.53% of their target molecules (estradiol and gestrinone, respectively) at a nominal loading of 20 ≈μg in 50 mg of NPs. This work highlights the potential of these bi-functional materials for trace material clean-up of complex samples and/or subsequent analysis and opens up possibilities for further simple, rapid-to-synthesise materials for targeted clean-up.