Amorphous silica nanoparticles (nSP50) exacerbate hepatic damage through the activation of acquired cell-mediated immunity

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. However, 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.

Evaluation of the Potential of Nanofluids Containing Different Ag Nanoparticle Size Distributions for Enhanced Solar Energy Conversion in Hybrid Photovoltaic-thermal (PVT) Applications

Hybridising photovoltaic and photothermal technologies into a single system that can simultaneously deliver heat and power represents one of the leading strategies for generating clean energy at more affordable prices. In a hybrid photovoltaic-thermal (PVT) system, the capability to modulate the thermal and electrical power output is significantly influenced by the spectral properties of the heat transfer fluid utilised. In this study, we report on one of the first experimental evaluations of the capability of a multimodal silver nanofluid containing various particle shapes and particle sizes to selectively modulate the solar energy for PVT applications. The diverse set of particle properties led up to a 50.4% enhancement in the solar energy absorbed by the nanofluid over the 300 nm – 550 nm spectral region, where silicon is known to exhibit poor photovoltaic conversion performances. This improved substantially the absorption of solar energy, with an additional 18 – 129 W m-2 of thermal power being generated by the PVT system. Along with the advancements made in the thermal power output of the PVT system, a decrease of 4.7 – 36.6 W m-2 in the electrical power generated by the photovoltaic element was noted. Thus, for every ~11 W m-2 increase of thermal power achieved through the addition of the nanoparticles, a reduction of ~3 W m-2 in the ability to generate clean electricity was sustained by the PVT. Despite the energy trade-offs involved under the conditions of the nanofluid, the PVT system cumulatively harvested 405 W m-2 of solar energy, which amounts to a total conversion efficiency of 45%. Furthermore, the economics of the additional energy harvested through merging of the two systems was found to reach an enhancement of 77% under certain European conditions.

Recent advances in g-C3N4 based gas sensors for the detection of toxic and flammable gases: a review

In recent years, many 2D nanomaterials like graphene, MoS2, phosphorene, and metal oxide nanosheets have been investigated for gas sensing applications due to their excellent properties. Amongst other 2D nanomaterials, graphitic carbon nitride (g-C3N4) has attracted significant attention owing to its simple synthesis process, tunable electronic properties, and exceptional physicochemical properties. Such remarkable properties assert g-C3N4 as a potential candidate for the next-generation high-performance gas sensors employed in the detection of toxic and flammable gases. Although several articles and reviews are available on g-C3N4 for their synthesis, functionalities, and applications for the detection of humidity. Few of them has focused their attention on gas sensing using g-C3N4. Thus, in this review, we have methodically summed up the recent advances in g-C3N4 and its composites-based gas sensor for the detection of toxic and flammable gases. Moreover, we have also incorporated the synthesis strategies and the comprehensive physics of g-C3N4 based gas sensors. Additionally, different approaches are presented for the enhancement of gas sensing/detecting properties of g-C3N4 based gas sensors. Finally, the challenges and future scope of g-C3N4 based gas sensors for real-time monitoring of gases have been discussed.

Engineering sensitivity and spectral range of photodetection in van der Waals materials and hybrids

Exploration of van der Waals heterostructures in the field of optoelectronics has produced photodetectors with very high bandwidth as well as ultra-high sensitivity. Appropriate engineering of these heterostructures allows us to exploit multiple light-to-electricity conversion mechanisms, ranging from photovoltaic, photoconductive to photogating processes. These mechanisms manifest in different sensitivity and speed of photoresponse. In addition, integrating graphene-based hybrid structures with photonic platforms provides a high gain-bandwidth product, with bandwidths >> 1 GHz. In this review, we discuss the progression in the field of photodetection in 2D hybrids. We emphasize the physical mechanisms at play in diverse architectures and discuss the origin of enhanced photoresponse in hybrids. Recent developments in 2D photodetectors based on room temperature detection, photon-counting ability, integration with Si and other pressing issues, that need to be addressed for these materials to be integrated with industrial standards have been discussed.

Bouncing dynamics of electrostatically actuated NEM switches

The aim of the present research is to understand the bouncing dynamic behavior of nano electromechanical (NEM) switches in order to improve the 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.

Planar narrowband Tamm plasmon-based hot-electron photodetectors with double distributed Bragg reflectors

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.

Analysis of the charging kinetics in silver nanoparticles-silica nanocomposite dielectrics at different temperatures

Dielectric nanocomposite materials are now involved in a large panel of electrical engineering applications ranging from micro-/nano-electronics to power devices. The performances of all these systems are critically dependent on the evolution of the electrical properties of the dielectric parts, especially under temperature increase. In this study we investigate the impact of a single plane of silver nanoparticles (AgNPs), embedded in a thin silica (SiO2) layer close to the surface, on the electric field distribution, the charge injection and the charge dynamic processes for different AgNPs-based nanocomposites and various temperatures in the range 25°C – 110°C. The electrical charges are injected locally by using an Atomic Force Microscopy (AFM) tip and the related surface potential profile is probed by Kelvin Probe Force Microscopy (KPFM). To get deeper in the understanding of the physical phenomena, the electric field distribution in the AgNPs-based nanocomposites is computed by using a Finite Element Modeling (FEM). The results show a strong electrostatic coupling between the AFM tip and the AgNPs, as well as between the AgNPs when the AgNPs-plane is embedded in the vicinity of the SiO2-layer surface. At low temperature (25°C) the presence of an AgNPs-plane close to the surface, i.e., at a distance of 7 nm, limits the amount of injected charges. Besides, the AgNPs retain the injected charges and prevent from charge lateral spreading after injection. At 110°C the amount of injected charge is increased in the nanocomposites compared to low temperatures. Moreover, the speed of lateral charge spreading is increased for the AgNPs-based nanocomposites. These findings imply that the lateral charge transport is favored in the nanocomposite structures by the closely situated AgNPs because of the strong electrostatic coupling between them.

Study of thermoplasmonic properties of gold nanodimer in visible -infrared region of electromagnetic spectrum

In the present study, the heat generation in gold nanodimers 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 6nm. 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.

Role of Nanostructuring of Sensing Materials in Performance of Electrical Gas Sensors by Combining with Extra Strategies

Nanostructuring, including tailoring dimensionality, size and morphology, and nanopatterning, is well recognized to play an increasingly important role in sensing units/chips of electrical gas sensors. As two predominant and fundamental configurations, chemiresistor- and field emission transistor (FET)-based electrical gas sensors are receiving increasing attention for fundamental research and practical applications. Herein, state-of-the-art overviews of electrical gas sensors are presented with emphasis on the role of nanostructuring in sensing units for both chemiresistors and FETs types, the strategies for their performance enhancement, and some key sensing mechanisms involved. Nanostructuring of sensing units and their dependence of the performance of chemiresistor- and FET-based gas sensors are discussed according to zero- (0D), one-(1D), two- (2D), and three-dimension (3D), respectively. Other types of gas sensors are also mentioned briefly. Some particular strategies such as loading external heat and light sources, electrical field, and mechanical forces for providing extra freedom to improve and optimize the performance are introduced in detail. Finally, a summary and future perspectives about gas sensors are given with some novel strategies, ideas, and solutions that could make it possible to meet the requirements of rapid industrialization, informatization, intelligentization, and population expansion.

Effect of point defects and nanopores on the fracture behaviors in single-layer MoS2 nanosheets

Point defects and nanopores are inevitable and particularly noticeable in single-layer (SL) MoS2. Molecular dynamics (MD) simulations have been done to comprehensively study the influences of point defects and nanopores on tensile deformation behaviors of SLMoS2 nanosheets, and the dependences of fracture properties on defect type and concentration, pore size, temperature and strain rate are discussed. The formation energy of S vacancy (VS) is the lowest one, but that of VMoS6 is the highest one, corresponding to the highest and lowest fracture stress, respectively. The local stress concentration around point defects and nanopores might lead to the early bond breaking and subsequent nucleation of cracks and brittle fracture upon tensile loading. A modified Griffith criterion is proposed to describe the defect concentration and pore size dependent fracture stress and strain. These findings provide us an important guideline for the structural design of 2D materials in future applications.