Table of contents

Energetic materials (EMs) are a group of distinctive materials that release an enormous amount of amassed chemical energy in a short time when incited by external mechanical or thermal factors. They comprise of propellants, explosives, and pyrotechnics. Unlike conventional micro-energetic materials, nano energetic materials (nEMs), due to their smaller particle size ranging from 1–100 nm, exhibit higher specific surface area (~10–50 m² g⁻¹), reduced ignition temperatures from 2350 K to approx.1000 K for particle size from 100 μm to 100 nm respectively, higher energy densities (up to 50 MJ kg⁻¹), burning rates ~30.48 mm s⁻¹ at 6.894 kPa with specific impulses up to 542 s (5320 m s⁻¹), low impact sensitivity (<4–35 J). Such exceptional properties of nano energetic composites, i.e., thermites (a combination of metal-fuel/metal oxide particles), find applications, namely in, munitions, pyrotechnics, energetic micro-electromechanical system (MEMS) chips. This review provides valuable insight into the synthesis methods of nano energetic composite systems (e.g., Al/CuO, Al/KMnO₄, Al/Fe₂O₃, Al/SnO₂, Silicon-based systems), their characteristic properties, behavior under certain conditions and applications. Furthermore, the review converses about the advancements made in the last few decades by many researchers, along with the technological gaps that need to be addressed for futuristic applications.

Chiral nanostructures are asymmetric nanoarchitectures that cannot be superimposed with their mirrored-symmetric counterparts, which have attracted considerable attention due to their special photophysical properties and potential applications in plasmonics, spectroscopy and nanosensors. In particular, Self-Assembly of chiral nanostructures with symmetric or asymmetric objects might exhibit exceptional optical activity because those chiral superstructures can manipulate chiral states of light that leads to circular dichroism (CD) effect. This review highlights recent advances on the self-assembly of plasmonic chiral superstructures from simpler dimeric, and trimeric chiral nanoassemblies to complicated chiral nanoarchitectures, especially emphasizes the resulted superior optical activity and the corresponding principles.

Nowadays, the deadly viruses (including the latest coronavirus) and pathogens transmission became the major concern worldwide. Efforts have been made to combat with these fatal germs transmitted by the airborne, human-to-human contacts and contaminated surfaces. Thus, the antibacterial and antiviral materials have been widely researched. Meanwhile, the development of diverse nanomaterials with the antiviral traits provided several benefits to counter the threats from the surface and airborne viruses especially during the Covid-19 pandemic. Based on these facts, this paper overviewed the advantages of various nanomaterials that can disinfect and deactivate different lethal viruses transmitted through the air and surfaces. The past development, recent progress, future trends, environmental impacts, biocidal effects and prospects of these nanomaterials for the antiviral coating applications have been emphasized.

In recent times, there has been rapid progress and achievement in the development of nanoparticle production in a microfluidic environment. Microfluidics technology harnesses the fluid mechanics to generate nanoparticles with a unique size and finely controllable shape that can be used for various applications like drug delivery, biological sciences, healthcare, and food industries. The nanoparticles are generally distinguished from fine particles to coarse particles due to their smaller size and unique material properties like chemical, physical, biological, and optical. However, the conventional methods require bulky instruments, expensive autoclaves, consume more power, high thermal loss, and require more time for the synthesis. Further, it is very challenging to automate, integrate, and miniaturize the conventional device on a single platform for synthesizing micro-and nanoscale particles. There has been considerable advancement in the development of microfluidic devices in the last few years for nanoparticle synthesis. The microfluidic device unveils several features such as portability, transparency in operation, controllability, and stability with a marginal reaction volume. The microfluidic-based nanoparticle synthesis also allows rapid processing and increased efficiency of the technique by using minimum peripherals for its operation. In this review article, we have discussed the microfluidic devices that are used for synthesizing various nanoparticles for different applications. This review summarizes the value-chain to develop microfluidic devices, including designs, fabrication techniques, and other related methodologies, to create nanoparticles in a controlled and selective manner.

In additive manufacturing, indirect laser sintering is used to process and fabricate ceramic materials using a polymer–ceramics green body. The mechanical strength of the green body is important to hold the shape and to enable the use of laser with low power density during the laser sintering process. Because the microstructure of the green body will considerably affect the density of the final product, this study demonstrated a feasible controlled formation of Poly (methylmethacrylate) (PMMA)–Al₂O₃ composite particles by an electrostatic assembly method that was used for the fabrication of the green body with improved mechanical properties, which were determine using an indentation test. The controllable homogeneous decoration of desired submicron-sized PMMA particles on Al₂O₃ particles allowed an effective use of PMMA additives while exhibiting considerable mechanical property improvement of the green body compared to poly(vinyl alcohol)-bonded Al₂O₃. The findings of this study show good potential of green body formation with improved strength for ceramics fabrication via indirect laser sintering.

The electronic properties of an infinite row of freestanding, aligned side-by-side, pentacene molecules are derived as a function of the intermolecular overlap integral and the chemical potential shift. We use a semiclassical approximation and a first principles tight binding method to obtain conductance and mobility of this one-dimensional crystal as a function of temperature and gate voltage. For two values of the intermolecular overlap, energy bands show a metallic behavior. For all the other values, a bandgap is present and evolves with the intermolecular overlap following a typical modulation. The magnitude of the scattering parameters estimated by the observed conductivity is coherent with the existing literature values. These findings could be relevant for the implementation of organic-based sensors.

The influence of alumina nanofiller and gamma irradiation on the surface potential variation of epoxy-alumina nanocomposites was investigated. The surface potential decay rate of nanocomposites has increased and the trap depth decreased with alumina nanoparticles addition to the matrix as well as upon exposure to gamma irradiation, Surface roughness was estimated using the wavelets and fractal technique. Daubechies wavelet of order 4 (db4) wavelet was chosen as the most suitable mother wavelet for surface roughness measurement. Multi resolution signal decomposition (MRSD) analysis of surface profile has revealed that with increasing wt% of alumina nanofiller in the nanocomposites, reduction in surface roughness of nanocomposites was observed. Upon gamma irradiation, the surface roughness factor at each level of MRSD has increased marginally. Fractal dimension and lacunarity were calculated for unaged and gamma ray irradiated samples and it exhibits inverse correlation.

Methicillin-resistant Staphylococcus aureus (MRSA) causes mastitis in dairy cattle with serious economic and public health significance. This study developed nanoemulsions of Linum usitatissimun oil loaded with Achyrocline satureioides (macela) extract and investigated their in vitro antimicrobial activity against MRSA. Macela-nanoemulsions (NE-ML) were prepared using high-pressure homogenization (HPH) with different proportions of flaxseed oil, Tween 80 and crude extract. Four majoritarian flavonoids were identified in the macela extract: 3-O methylquercetin, achyrobichalcone, quercetin and luteolin (187.3 ± 0.1, 155.4 ± 11.6, 76.3 ± 0.1 and 30.4 ± 0.0 μg ml⁻¹, respectively). NE-ML nanoemulsions were successfully obtained by the HPH method and showed a milky aspect with yellowish color. The mean particle size was around 200 nm with monodisperse distribution (PdI < 0.2), remaining stable for 160 days at room temperature. When analyzed on a LUMiSizer high-end dispersion analyzer, low values were found (≤0.5), indicating high stability index, mainly for NE-ML1:5 (0.2). The encapsulation efficiency of macela-nanoemulsions was greater than 94%, considering the four chemical compounds from extract. Minimum inhibitory concentration (MIC) against planktonic bacteria, inhibition of biofilm formation (MBIC), and eradication of MRSA biofilms (MBEC) were determined through in vitro tests on microplates. The MIC of NE-ML against planktonic MRSA showed values ranging from 1.2 to 10% (v/v), while blank-nanoemulsions (NE-B, without macela extract) showed values ranging from 6 to 50% (v/v). MBIC and MBEC of NE-ML were 25 and 80% (v/v), respectively. MBIC showed a mass reduction greater than 64%, and MBEC showed a mass reduction greater than 73%. Macela-nanoemulsions (NE-ML), mainly NE-ML1:5, showed high antimicrobial activity and appeared to represent a new alternative of sustainable antimicrobial product for the control of MRSA. Since this innovative nanoemulsion can impact animal health, future research should include in vitro and in vivo studies to evaluate intramammary therapy and control of MRSA infections in organic and agroecological milk production systems.

This paper describes the development of a novel method of producing nanocomposites consisting of gold nanoclusters anchored on graphene oxide nanosheets in a cost-effective and reproducible manner. The novelty of the technique hinges on the covalent functionalization of atomically precise subnanometer gold clusters protected by glutathione (Au₁₅SG₁₃ and Au₂₅SG₁₈) on to graphene oxide (GO) nanosheets according to the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride crosslinking method, using the existing carboxylic groups present both at the surfaces of the nanoclusters and the GO nanosheets. The atomic precision of glutathione-protected gold nanoclusters was evidenced by electrospray ionization mass spectrometry. The formed hybrid nanocomposites were characterized by TEM measurements and exhibit nonlinear optical properties characteristic of GO, in particular a strong second harmonic scattering response as well as a multi-photon excited fluorescence spectrum characterized by a broad band in the visible range between 350 and 700 nm. Atomically precise nanoclusters covalently linked to GO nanosheets are therefore promising for new applications in the areas of optoelectronics and photovoltaics.

Nanoparticles (NPs) are extensively being used in state-of-the-art nano-based therapies, modern electronics, and consumer products, so can be released into the environment with enhancement interaction with humans. Hence, the exposures to these multifunctional NPs lead to changes in protein structure and functionality, raising serious health issues. This study thoroughly investigated the interaction and adsorption of catalase (CAT) with HfO₂-NPs by circular dichroism (CD), Fourier transform infrared (FTIR), absorption, and fluorescence spectroscopic techniques. The results indicate that HfO₂ NPs cause fluorescence quenching in CAT by a static quenching mechanism. The negative values of Vant Hoff thermodynamic expressions (ΔH^o, ΔS^o, and ΔG^o) corroborate the spontaneity and exothermic nature of static quenching driven by van der Waals forces and hydrogen bonding. Also, FTIR, UV-CD, and UV–visible spectroscopy techniques confirmed that HfO₂ NPs binding could induce microenvironment perturbations leading to secondary and tertiary conformation changes in CAT. Furthermore, synchronous fluorescence spectroscopy confirmed the significant changes in the microenvironment around tryptophan (Trp) residue caused by HfO₂ NPs. The time depending denaturing of CAT biochemistry through HfO₂-NPs was investigated by assaying catalase activity elucidates the potential toxic action of HfO₂-NPs at the macromolecular level. Briefly, this provides an empathetic knowledge of the nanotoxicity and likely health effects of HfO₂ NPs exposure.

Doxorubicin (DOX) is a traditional broad-spectrum antitumor drug, which has a wide range of clinical applications, but has no tumor non-specificity. Nanoparticles have been explored as drug delivery agents to enhance the therapeutic efficacy and reduce toxic and side effects. Carbon dots (CDs), a carbon-based nanomaterial, has many unique advantages such as easy synthesis, good biocompatibility, and low toxicity. In this study, folic acid was used as raw material to prepare new CDs, and DOX was loaded on the surface of CDs through electrostatic interaction. The prepared nano-drugs CDs/DOX could effectively release DOX under mild acidic pH stimulation. Cell imaging showed that CDs/DOX could transport doxorubicin (DOX) to cancer cells and make them accumulated in nucleus freely. Flow cytometry tests and cellular toxicity assay together confirmed that CDs/DOX could target tumor cells with high expression of folate receptor and increase anti-tumor activity. The therapeutic effect on 4T1 tumor-bearing mice model indicated that CDs/DOX could alleviate DOX-induced toxicity, effectively inhibit tumor growth, and prolong the survival time. Hence, such a targeting nanocarrier is likely to be a candidate for cancer treatment.

Small droplets exist in nature widely and have attractive applications. Although there are some well-established techniques to produce small droplets, it is still a substantial challenge to generate and measure the volume of ultrafine droplets down to attolitres (aL) precisely. Here, we accurately generate ultrafine droplets in attolitre scale by an electrohydrodynamic jet method. By superimposing a low frequency pulse over a static electric field, the volumes of the ultrafine droplets are accurately controlled from 1 to 5 aL with the best accuracy of 0.3 aL and coefficient of variations less than 25%. Gold nanoparticles are deposited on substrate directly from the ultrafine droplets of HAuCl₄/H₂O solution through a confined reaction in a reducing environment. The gold nanoparticles exhibit highly sensitive and reproductive in surface-enhanced Raman scattering.

In the present work, amine-functionalized nanodiamonds (NDs) have been encapsulated in liposomes and studied in order to observe the modification of their photoluminescence properties. NDs were functionalized with aromatic amines such as 1-aminopyrene and 2-aminofluorene, and the aliphatic amine 1-octadecylamine. Morphology, structural and optical properties of NDs and amine-modified NDs were analyzed by transmission electron microscopy, atomic force microscopy, scanning electron microscopy, and photoluminescence. The amine-functionalized NDs were successfully encapsulated in lecithin liposomes prepared by the green and conventional methods. The obtained results show significant changes in photoluminescent properties of functionalized NDs, and were more potentialized after liposome encapsulation. Our findings could be applied in the development of new kinds of water-dispersible fluorescent hybrids, liposome-NDs, with the capability of drug encapsulation for use in diagnostics and therapy (theragnostic liposomes). All-optical sensors with possibilities for tailoring their response for other biomedical applications can be also contemplated.

In this work, we report a simplified method to measure thermal conductivity from the typical Raman thermometry method by employing a much simpler dispersion relationship equation and the Debye function, instead of solving the heat equation. Unlike the typical Raman thermometry method, our new method only requires monitoring of the temperature-dependent Raman mode shifting without considering laser power-dependent Raman mode shifting. Thus, this new calculation method offers a simpler way to calculate the thermal conductivity of materials with great precision. As a model system, the β-Ga₂O₃ nanomembrane (NM) on a diamond substrate was prepared to measure thermal conductivity of β-Ga₂O₃ NMs at different thicknesses (100 nm, 1000 nm, and 4000 nm). Furthermore, the phonon penetration depth was investigated to understand how deep phonons can be dispersed in the sample so as to guide the dimensional design parameter of the device from the thermal management perspective.

The present study explores biosynthesis of silver nanoparticles (AgNPs) employing extracellular extract of Aspergillus terreus ITCC 9932.15. Modulation of various variables that dictate the biosynthesis of AgNPs, suggested of optimal AgNPs synthesis using AgNO₃, 1 mM at pH 8 and temperature, 35 °C. The biosynthesis of AgNPs was observed to be time dependent with incremental particle synthesis till 24 h. Various studies were undertaken to authenticate formation and characterization of AgNPs for size, crystallinity and biomolecules involved. A sharp SPR peak observed at 420 nm in the UV–vis absorption spectra validated synthesis of nanoparticles. These particles exhibited spherical morphology with size ∼25 nm and −16 mV of zeta potential. Further, the existence of proteins and other biomolecules onto the surface of AgNPs was confirmed with FTIR studies. The SAED pattern investigated by employing TEM authenticated the crystallinity of AgNPs. The AgNPs also exhibited potential antibacterial activity against Gram-negative and Gram-positive bacteria (E. coli and P. aeruginosa). In addition, remarkable anticancer activity was obtained in breast cancer cell line (MCF-7).

Boron nitride (BN) supported palladium (Pd) nanostructured catalyst, as an alternative support for heterogeneous reduction of nitrobenzene derivatives, was prepared by a mild reduction of a Pd precursor in water. The structural characteristics and distribution of the synthesized Pd nanoparticles (NPs) on BN support were investigated by transmission electron microscopy, scanning transmission electron microscopy, energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy methods. The potential and efficiency of the BN supported Pd NPs as an active and stable nanostructured catalyst were verified in the reduction of nitroaromatics. Excellent yields of the corresponding aryl amines in water were obtained and due discussion were included about the catalytic activity of the synthesized catalyst. It was also indicated that the nanostructured catalyst can be recycled at least for six consecutive cycles in the reduction of nitrobenzene, without losing significant activity.

Polyvinyl alcohol/surfactant-free single-walled carbon nanotube (PVA/SF-SWNT) nanocomposites were synthesized by a facile solution-cast technique. The effect of SF-SWNT on the structural, surface-morphological, mechanical, electrical, and electrochemical properties of the nanocomposite was studied. The surface morphology and Fourier Transform Infrared Spectroscopy demonstrate an increased degree of interaction between PVA and SF-SWNT resulting in improved mechanical strength of the nanocomposite. Incorporation of SF-SWNT was found to improve the DC electrical conductivity by almost five orders of magnitude. Furthermore, the effect of SWNT on the electrochemical properties of the nanocomposite was also studied. The PVA/SF-SWNT composite exhibits specific capacitance as high as 26.4 F g⁻¹ at a current density 0.5 mA g⁻¹, which is four times higher than that of PVA (6.1 F g⁻¹). The impedance spectroscopy analysis reveals that the incorporation of SWNT reduces the charge transfer resistance of the nanocomposites resulting in better capacitive performance.

Silicon nanowire has been perceived as one of the most promising anodes in the next generation lithium-ion batteries (LIBs) due to its superior theoretical capacity. However, its high-cost and complicated fabrication process presents significant challenges for practical applications. Herein, we propose a simple scalable process, thermal-alkaline treatment followed by sputtering deposition, for preparing a unique self-standing anode of three-dimensional (3D) porous Si–TiO₂ web-nanowired nanostructure for micro-LIBs. One-step thermal-alkaline synthesis of TiO₂ nanowire scaffolds (TNS) with well-controlled thickness of 600–800 nm is reproducibly obtained onto Cu foils, achieving a 3D porous geometry for further growing Si active materials onto it to form 3D web-nanowired TiO₂-Si composite material with interstitial voids. Profiting from the coverage of Si, direct contact of active materials on current collector, and the unique 3D web-nanowired structure, it exhibits high reversible volumetric charge capacity of 2296 mAh cm⁻³ with a coulombic efficiency of ∼95%, higher capacity retention, better capacity recovery ability and improved rate capability. Importantly, this work paves a simple way to directly build reliable 3D nanostructures or nanowired frameworks on selected current collectors as self-standing anodes for high volumetric capacity microbatteries; thus it is easy to scale up and beneficial for microelectronics industry.

Mesoporous strontium doped ZnO nanoparticles are synthesized as photocatalyst by using zinc nitrate hexahydrate, surfactant P123, strontium nitrate hexahydrate via the hydrothermal process. X-ray diffraction (XRD), UV-visible spectroscopy (UV), Fourier transform infrared (FTIR), Photoluminescence (PL), Energy-dispersive x-ray (EDX), Scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET) characterizations are used for the analysis of all the samples. XRD spectra disclose the disparity in the crystal size 14.98 to 22.74 nm. The study of UV spectroscopy revealed the energy bandgap difference between 3.3–2.92 eV. PL spectroscopy shows the effect of doping on the electron-hole recombination rate of the sample. FTIR analysis has utilized to determine the functional groups such as –OH, C=O=C, and –C–O present in the sample. EDX spectra show the elemental compositions of the sample. SEM images show the agglomerated morphology and TEM images show the different shape morphology of the sample. BET analysis shows the occurrence of 39.9 m² g⁻¹ surface area with mesoporous morphology. The effect of the increasing percentage of strontium on the photocatalytic capability of ZnO is checked against methylene blue and congo red dyes with 75% and 80% degradation.

An n-i-p type of organic-inorganic hybrid bifacial solar cells was constructed with a ZnO/polyaniline/NiO_x heterostructure, in which vertically aligned ZnO nanorods (ZnO_Nd) were synthesized by a facile electrochemical deposition process and act as an electron-transport layer. Semitransparent p-type semiconducting NiO_x films were utilized as a hole-transport layer. Devices based on the ZnO_Nd considerably outperform those employing ZnO thin films. The contact and electrical properties of NiO_x can be carefully tuned through controlling the deposition parameters as well as surface treatments. Intimate contact between NiO_x with PANI, created by in situ electrochemical polymerization, greatly improves the charge movement. Furthermore, an O₂-plasma treatment of the NiO_x film has a significant impact on the performance of polyaniline/ZnO_Nd hybrid photovoltaic devices, reflected by the enhancement in the fill-factor and efficiency. The power conversion efficiency of the ZnO_Nd/PANI/NiO_x device under the optimized O₂ plasma condition can reach up to 2.79% under AM1.5 illumination.

A comparative study was done on three types of TiO₂ thin film morphology, i.e., mesoporous nanoparticles, nanorods, and nanobranched nanorods thin films, as the scaffold for the perovskite solar cell. The performances of the perovskite-coated thin films were compared in terms of charge carrier extraction, charge transport, and solar energy harvesting via photoluminescence and UV–vis spectroscopies. TiO₂ nanobranched nanorods thin film showed better photovoltaic performance than those of mesoporous nanoparticles and nanorods thin films. The better optical properties of nanobranched nanorods thin film as the scaffold is ascribed to its unique morphological advantages, i.e., remarkable specific surface area along with high-speed pathways for charge carriers. These characteristics lead to great, compact, and uniform perovskite loading, excellent electron transport property, and desired light harvesting performance, which are preferable features for promoting the efficiency of the perovskite solar cells. This paper introduces an outstanding scaffold for fabrication of high-performance perovskite solar cells.

This study reports solution combustion synthesis of magnesia nanoparticles (nMgO) using magnesium nitrate as oxidiser and glycerol as fuel. Size, morphology, crystal structure and surface properties of synthesised nMgO were analysed by PXRD, SEM, TEM, FTIR and Point of Zero Charge. The XRD pattern of nMgO confirmed prepared samples were single cubic-phase without any impurities. TEM analysis proved nMgO was in nano regime with an average particle diameter of 20–40 nm. FTIR spectra show the presence of characteristic peaks of nMgO and support the XRD results. The prepared nMgO was employed as an adsorbent for the removal of two anionic dyes viz. Indigo Carmine (IC) and Orange G (OG). Furthermore, various adsorption isotherms and kinetic models were performed to understand the kinetics and mechanism of the adsorption process. Experimental results demonstrated that the adsorption equilibrium data fit well to Sips isotherm (R² > 0.98) and the saturated adsorption capacities of nMgO were found to be 262 mg g⁻¹ for IC and 126 mg g⁻¹ for OG. Adsorption kinetics analysis revealed that the adsorption followed pseudo-first-order model, with both film and pore diffusion governing the rate of adsorption. Excellent adsorption capacity combined with efficient regeneration proved the potential of the prepared nMgO as an adsorbent for the removal of harmful dyes from industrial effluent.

A new type on-chip electron source based on electroformed SiO_x is recently reported to show dense and efficient electron emission under low working voltage. Here we study the effect of the Si doping type of SiO_x/Si substrate on the performances of the SiO_x-based electron source fabricated on it. The electron source is composed of an array of parallelly integrated micro-emitters. Each micro-emitter is composed of a square nanogap with a width about 100 nm which is spaced by two concentric graphene films on the SiO_x substrate. The inner graphene film contact with bottom Si electrode through a via hole opening to the bottom Si layer and the outer graphene film contact with the common metal electrode. Effective emission current and efficiency of the electron source are found to be significantly influenced by both the polarity of the driven voltage applied between the metal electrode and bottom Si layer and the polarity of the Schottky barrier at graphene-Si contact. The performances of electron sources can be optimized by choosing n-type doping of SiO_x/Si substrate to make the positive influence of the two aspects achieved at the same time. An emission current up to 100 μA and emission density of 250 mA cm⁻² are achieved for an optimized device with 64 micro-emitters at bias voltage of 32.8 V.

Our work involves the growth of well aligned vertical nanorods of ZnO on transparent indium doped tin oxide (ITO) conductive substrate and fabrication of Au/ZnO Nanorods/ITO Heterojunction device. The observation of non-ideal diode current density-voltage (J-V) characteristics of the device has been evaluated with various conduction mechanisms [Ohmic, space-charge limited conduction (SCLC)]. The charge carrier mobility is estimated to be ∼0.05 cm²/Vs. The presence of deep level defects in the ZnO nanorods is accountable for these two different transport mechanisms and it is backed by photoluminescence, distinctly. The estimated density of deep trap states is n_trap ∼ 5.76 × 10¹³ cm⁻³. The charge carrier density and built-in potential of this device are obtained from electrochemical impedance spectroscopy (EIS). The average work function of vertical ZnO nanorods is found out to be ∼4.93 eV. Henceforth, our results explain the charge transport mechanism which plays a key role in optoelectronic based devices for various applications.

Nanotechnology continuously rises due to its potential applications. To control nano-materials design and microstructure, it is very essential to understand nucleation and crystalline growth in these materials. In this research contribution, crystallization kinetics and thermal behaviour of nano-crystalline Se_79-xTe₁₅In₆Pb_x (x = 0, 1, 2, 4, 6, 8 and 10 at. wt%) chalcogenide alloys is analyzed through differential scanning calorimetry (DSC) process under non-isothermal conditions at four different heating rates; 5, 10, 15 and 20 °C min⁻¹. The examined Se-Te-In-Pb nano-chalcogenide system is prepared through melt-quenching process. Characteristic temperatures namely glass transition temperature (T_g), onset crystallization temperature (To), peak temperature of crystallization (T_p) and melting temperature (T_m) show dependence on heating rate and composition. The various kinetic parameters such as activation energy of glass transition (E_g), activation energy of crystallization (E_c), reduced glass transition temperature (T_rg), Hruby number (K_gl), thermal stability parameters (S and H') and fragility index (F_i) are analyzed for investigated Se-Te-In-Pb nano-crystalline system. Different empirical approaches are applied to determine the apparent glass transition activation energy (E_g) and crystallization activation energy (E_c).

We have investigated molecule adsorption phenomena on a chemically active surface of titanium oxide nanosheet by coupling with an electrically sensitive graphene field effect transistor (FET). Super-hydrophilic surface of the titanium oxide nanosheet forms a water-layer in ambient air which exhibits a large hysteresis of drain current in the hybrid FET for sweeping gate-voltage. The large hysteresis disappears in vacuum, which indicates physically adsorbed water molecules on the surface of the titanium oxide nanosheet dominantly contribute to the hysteresis. UV light irradiation in vacuum significantly changes the drain current due to desorption of the adsorbed molecules. Sufficient UV irradiation results in symmetric gate-voltage dependence similar to those of conventional graphene FETs. Exposure to an oxygen gas atmosphere leads to a heavy hole doping in the FET, where the binding of the oxygen molecules is stronger than that of water molecules. In a humidified nitrogen atmosphere, a large shift of charge neutrality point is observed in transfer characteristics crossing between electron doping and hole doping. By contrast, a clear square-shaped hysteresis loop is observed in a humidified oxygen atmosphere, where the hole density in the graphene drastically changed with O₂/H₂O redox couple reaction on the titanium oxide nanosheet.

Electrical contact resistance (ECR) measurements performed via conductive atomic force microscopy (C-AFM) suffer from poor reliability and reproducibility. These issues are due to a number of factors, including sample roughness, contamination via adsorbates, changes in environmental conditions such as humidity and temperature, as well as deformation of the tip apex caused by contact pressures and/or Joule heating. Consequently, ECR may vary dramatically from measurement to measurement even on a single sample tested with the same instrument. Here we present an approach aimed at improving the reliability of such measurements by addressing multiple sources of variability. In particular, we perform current-voltage spectroscopy on atomically flat terraces of highly oriented pyrolytic graphite (HOPG) under an inert nitrogen atmosphere and at controlled temperatures. The sample is annealed before the measurements to desorb adsorbates, and conductive diamond tips are used to limit tip apex deformation. These precautions lead to measured ECR values that follow a Gaussian distribution with significantly smaller standard deviation than those obtained under conventional measurement conditions. The key factor leading to this improvement is identified as the switch from ambient conditions to a dry nitrogen atmosphere. Despite these improvements, spontaneous changes in ECR are observed during measurements performed over several minutes. However, it is shown that such variations can be suppressed by applying a higher normal load.

Pd as cathodic catalyst exhibits relatively low current density in mixing kinetic/diffusion controlled region. To improve catalytic activity of Pd, alloying Pd with another transition metal is an effective approach. Here, we prepared carbon-supported Pd-Ir nanoalloys (Pd-Ir/C) through impregnation method. Four types of Pd-Ir/C were designed and referred as Pd₁₉Ir/C, Pd₉Ir/C, Pd₃Ir/C, and PdIr/C using nominal Pd/Ir atomic ratios of 19:1, 9:1, 3:1, and 1:1, respectively. The results showed that Pd and Ir formed the nanoalloy structures and Pd-Ir/C exhibited significantly improved catalytic activity for oxygen reduction reaction than Pd/C, indicating that Ir had important effect on Pd-Ir nanoalloys.

ZrO₂ (Zirconia) nanoparticles (NPs), PANI (polyaniline), and ZrO₂/PANI nanocomposites (NCs) were successfully synthesized using CTAB (Hexadecyltrimethylammonium bromide) and SDS (Sodium dodecyl sulfate) surfactants by following the co-precipitation method. The structural phase analysis of as-prepared, annealed nanoparticles, and nanocomposites was done using the XRD (x-ray diffraction) technique. The crystallite size of pure SDS and CTAB assisted ZrO₂ NP_S comes out to be 19 and 17 nm, respectively. After the formation of NCs, the size has been reduced to 15.7 and 15.9 nm, respectively for the same samples. The effect of surfactants on the dye adsorption mechanism was studied using XRD and UV–vis spectroscopy. The prepared NPs and NCs were utilized as an adsorbent for the removal of organic dye methylene blue (MB) which is used as a model compound. UV–vis spectra of the supernatant solution were taken and studied to detect the relative decrease in the dye concentration with time. The as-prepared CTAB assisted ZrO₂/PANI NCs show higher adsorption activity than annealed CTAB assisted ZrO₂/PANI whereas a reversal trend in the adsorption activity was observed for SDS-assisted ZrO₂/PANI NCs. Various kinetic models were implemented and correlated to the experimental data to elucidate the working mechanism for dye adsorption and to set up, a relation in the adsorption activity of surfactant modified NPs and NCs.

Here we report a drastic enhancement of nonlinear absorption behaviour and exceptional optical limiting action of two core-shell systems (Au@graphite and Ag@graphite) prepared by adopting a fairly easy way in which we did not use any graphitic substrate. We carried out pulsed laser ablation of Au and Ag targets in toluene, monosubstituted benzene from which graphite layers of nanometer thickness has emerged as a result of photochemical reactions. The prepared samples were characterized and analyzed by UV/Vis spectroscopy, Raman spectroscopy, and TEM. Theoretical simulations of the core-shell nanostructures were done by the finite-difference time-domain method underlined the quenching of SPR in the case of both Au and Ag NPs by the graphitic layers evolved from toluene. Au and/or Ag@graphite core-shell structure exhibited a huge improvement in the nonlinear absorption behaviour and the optical limiting efficiency of these systems is found to be better than that of many benchmark optical limiters. The enhancement in nonlinear absorption property and the limiting actions of these systems were attributed to the enhanced excited-state absorption as well as free-carrier absorption arose as a result of the modification in the electronic structure of graphite on core-shell formation. Moreover, the metallic NPs also enhances nonlinear absorption through free-carrier absorption free-carrier absorption. So we believe these results are quite useful for guiding the characterization, monitoring the synthesis of similar nanostructures and for, the development of nanohybrids with desired properties for nonlinear optical, optoelectronic and photocatalytic applications.

Observation of granular superconductivity and percolative ferromagnetism in hydrogen/oxygen doped graphite materials has motivated recent research because of the unexplored scenarios in the field of magnetic-devices and spintronics. Here we report a novel investigation of the effects of hydrogen-peroxide-doping on the magnetic properties of grafoil, highly oriented pyrolytic graphite (HOPG) and carbon nanotube (CNT) samples characterized by specific defective characteristics. ZFC and FC magnetic curves acquired on the undoped boundary-defect-rich grafoil samples from 2 K to 300 K, revealed a spin-glass-like behaviour, with magnetic irreversibilities indicating the existence of percolative ferromagnetism. An enhancement in such effect was found in the post-doped samples below ∼70 K, together with a magnetic transition. This was evidenced further by ESR, with the appearance of a broad differential absorption peak at 77 K for g ∼ 3.54, compatible with antiferromagnetic ordering in presence of ferromagnetic multilayers. An analogous enhancement of ferromagnetic signals was found on sp³-defect-rich HOPG, with the appearance of localized ESR differential absorption features at g factors of ∼ 2.14, ∼2.08, ∼2.02, ∼ 1.91 and ∼ 1.86 at 77 K. Instead, comparisons performed in vacancy-rich doped CNTs revealed a significantly different trend, with an anomalous demagnetization of both the vacancy-rich graphitic CNT layers and encapsulated Fe₃C nanowires. These observations seem to highlight a possible role of specific defects towards modifications of magnetic correlation in presence of hydrogen/oxygen species.

Zinc Oxide (ZnO) nanoparticles were synthesized by hydrothermal method under different conditions and studied various properties. FTIR studies proved the presence of ZnO bonding and purity of the samples. Grain size was found to be decreased with the increase of reaction temperature and increased with reaction time. TEM images show formation of nanorods under same reaction temperature, also nanoflowers and nanospheres for different temperatures. Intensity of luminescence peaks is found to be changed with variation in interplanar spacing. UV–vis spectra helped to identify the increased photon absorption in particles of bigger size. Change in bandgap value is also observed due to the difference in size of nanoparticles.

The very high cost, scarcity and dissolubility of platinum (Pt) is the center of debates as a counter electrode (CE) in dye sensitized solar cells (DSSCs) research domain. To deal with such core issues, herein, novel low-cost and electro-catalytically active inter-metallic nickel aluminide (Ni₃Al) thin films have been fabricated successfully on fluorine-doped tin oxide substrates by DC magnetron sputtering at room temperature. For the first time, Ni₃Al has been utilized as a CE for DSSCs application. Further, the solar cell performance of Ni₃Al based DSSC has compared with the sputtered coated Pt thin film based DSSC performance. Under open atmospheric experimental preparation conditions (in air), a maximum power conversion efficiency of 3% has been achieved with Ni₃Al CE. The obtained efficiency is quite analogous to a DSSC fabricated with a Pt CE. Further, as-fabricated Ni₃Al CEs have exhibited better electrochemical catalytic activity and anti-corrosion effect than that of sputtered Pt CEs. The low-cost and excellent electrocatalytic properties of intermetallic Ni₃Al thin films may pave the way towards development of Pt-free CE for DSSCs.

We report a rapid, robust and efficient technique for the fabrication of poly(methyl methacrylate) based microreactors using laser engraver to synthesize ZnS quantum dots. We also present a comparative study of synthesis and photocatalytic activity of ZnS quantum dots by conventional beaker reactor and microfluidic route. The ZnS synthesized in a microfluidic reactor revealed the formation of well dispersed quantum dots with uniform size of 2.5 ± 1 nm and higher band gap (4.12 eV) as compared to the quantum dots prepared by beaker reactor method. In comparison to the degradation profile in a conventional bulk reactor, a remarkable enhancement in the photocatalytic activity of ZnS quantum dots in microfluidic reactor has also been observed for degradation of organic dyes (Rhodamine B and Methyl orange) under UV irradiation. The degradation efficiency of ZnS can further be tuned by controlling flow rate of dyes through the photocatalyst coated micro-reactor. Instant degradation with efficiency of 93% and 99% for rhodamine B and methyl orange respectively, were achieved when the flow rate was maintained at 50 μl min⁻¹. The microfluidic reactor also offers the prolonged photocatalyst stability, ensuring its reusability without significantly losing its efficiency. The ZnS quantum dots were also observed to have excellent antibacterial property thus inhibiting the growth of E. coli bacterial colonies even at a very low concentration of 10 μg ml⁻¹.

Spin–orbit interaction of light serves as an important property of light, which deals with the study of polarization and phase modulations in the light beam. These studies are essential and principal characeristics of light beam that have been used for most of the nanophotonics applications. Silver nanoparticles (Ag NPs) prepared via biosynthesis are used for one of such nanophotonics application in scattering via studying the light scattered through these nanoparticles. The silver nanoparticles Ag NPs were synthesized using green method, where reduction of silver ions to silver nanoparticles happen during the reaction of aqueous solution of Ag NO₃ with the biomolecules present in fresh leaf extract of Coleus amboinicus plant. The nanoparticles were characterized using UV-visible (UV–vis) spectroscopy, Transmission electron microscopy (TEM) and Fourier Transform Infrared (FTIR) spectroscopy. TEM analysis shows the wide size distribution of spherical shape nanoparticles with 80 nm average size. The study of polarization and phase changes in the scattered light field has been carried out using Stokes polarimetry in forward direction scattering. Under the preliminary measurements of Polarimetry, the modification in the polarization components was studied by demonstrating changes in the Stokes S₂, S₃ parameters, polarization orientation (ψ) and ellipticity angle (χ) using transverse magnetic (TM) polarized Gaussian light beam.

Electrochemically exfoliated graphene (eeG) layers possess a variety of potential applications, e.g. as susceptor material for contactless induction heating in dynamic electro-magnetic fields, and as flexible and transparent electrode or resistivity heating elements. Spray coating of eeG dispersions was investigated in detail as a simple and fast method to deposit both, thin conducting layers and ring structures on polycarbonate substrates. The spray coating process was examined by systematic variation of dispersion concentration and volume applied to heated substrates. Properties of the obtained layers were characterized by UV-VIS spectroscopy, SEM and Confocal Scanning Microscopy. Electrical conductivity of eeG ring structures was measured using micro-four-point measurements. Modification of eeG with poly(dopamine) and post-thermal treatment yields in the reduction of the oxidized graphene proportion, an increase in electrical conductivity, and mechanical stabilization of the deposited thin layers. The chemical composition of modified eeG layer was analyzed via x-ray photoelectron spectroscopy pointing to the reductive behavior of poly(dopamine). Application oriented experiments demonstrate the direct electric current heating (Joule-Heating) effect of spray-coated eeG layers.

All inorganic cesium lead halides (CsPbX₃, X = Cl, Br, I) are promising materials and have been developed in recent years for various optoelectronic devices and applications because of their excellent optoelectronic properties. Regardless of their excellent characteristics their stability is still uncertain and it is challenging task to obtain stable emission in CsPbX₃ perovskite quantum dots (PQDs), hence limiting their practical optoelectronic application. In this context, several approaches have been used like an-ion exchange, ion doping, and core–shell structure to enhance PQDs stability. Herein, we synthesized dual ion co-doped Al³⁺/Mn²⁺ CsPbCl₃ PQDs for stable light emitting diodes through traditional hot injection method for the first time. By adjusting molar concentration of Al³⁺/Mn²⁺ CsPbCl₃, co-doped PQDs were successfully prepared. The co-doped PQDs exhibit tunable emission, covering a wide range under UV excitation. Moreover, these high luminescent co-doped PQDs were used to fabricate WLEDs, displaying stable near white light emission with the chromaticity coordination at (0.35, 0.28). Some new evidence has emerged, although some aspects of Mn²⁺ and Al³⁺ doping are considered to be consistent with previous conclusions. This viewpoint incorporates all of these details and focuses on the path of transition metal ion doping to perovskite nanostructures and offers an overview for possible potential studies.

For the design of nanostructured semiconductor solar cells and photodetectors, optics modelling can be a useful tool that reduces the need of time-consuming and costly prototyping. We compare the performance of three of the most popular numerical simulation methods for nanostructure arrays: the Fourier modal method (FMM), the finite element method (FEM) and the finite-difference time-domain (FDTD) method. The difference between the methods in computational time can be three orders of magnitude or more for a given system. The preferential method depends on the geometry of the nanostructures, the accuracy needed from the simulations, whether we are interested in the total, volume-integrated absorption or spatially resolved absorption, and whether we are interested in broadband or narrowband response. Based on our benchmarking results, we provide guidance on how to choose the method.

We theoretically investigate the effect of nanoparticle(NP) inclusion on the lattice thermal conductivity (κ_l) of SnSe matrix. The theoretical approach involves the prediction of κ_l by varying the radius (R), density (D₁), and volume fraction (ε) of NP in SnSe matrix. NP has strong anisotropic effect on the lattice thermal conductivity reduction along the crystallographic direction. We observe the existence of an optimal NP volume fraction that minimizes the nanocomposite's thermal conductivity. At room temperature, this value is found to be ε = 0.317 for which lattice thermal conductivity reduces by 35% with NP (R = 5 nm) compared to pure SnSe. An enhancement in the figure of merit (ZT) around room temperature opens up new opportunities for thermoelectric power generation at moderate temperatures. Even larger enhancement is possible in polycrystalline SnSe which will be helpful for thermoelectric devices.

Synthesis of new piezoelectric materials to harness the vibrational and thermal energies may contribute to solve the current increasing energy demands. KNbO₃ is a known piezo- electric material that exhibits poor piezocatalytic activity owing to the scarcity of charge carriers in it. In order to enhance the charge carrier density in KNbO₃, extra electrons were added to KNbO₃ lattice. Extrinsic piezoelectric KNbO_3−x having extra electrons in the lattice was synthesized via the reaction between Nb₂O₅ and KBH₄ at elevated temperatures. The KNbO₃ nanostructures formed at 450 and 550 °C contained feebly piezoelectric KNbO_3−x/Nb₂O_5−x and piezoelectric KNbO_3−x respectively. The enhanced piezocatalytic activity of KNbO_3−x is demonstrated by the production of hydrogen from water by harnessing the mechanical vibrations and the observed hydrogen production rates are 0.05 and 3.19 ml h⁻¹ g¹ for KNbO_3−x/Nb₂O_5−x and KNbO_3−x respectively. The enhanced piezocatalytic activity of KNbO_3−x can be attributed to the enhancement of the charge carrier density resulting from the creation of oxygen vacancies in KNbO₃ that lead to enhancing the electronic conductivity as well as charge carrier separation. It is demonstrated that the piezocatalytic activity can be boosted by augmenting the charge carrier density in piezoelectric materials by synthesizing them under highly reducing reaction conditions.

Thin film hetero-structures (TFHSs) involving metal oxide thin films and noble metal nanoparticles are very important for many optoelectronics based device applications. This work reports the growth, characterization, and tuning of photoluminescence and I–V properties of TFHSs involving zinc oxide (ZnO) and gold nanoparticles (GNPs). ZnO thin films and GNPs were respectively deposited by the Pulsed Laser Deposition (PLD) and DC sputtering with subsequent annealing. Three different TFHSs were prepared by varying the relative positions of ZnO and GNPs, namely Si-GNPs-ZnO, Si-ZnO-GNPs, and Si-ZnO-GNPs-ZnO. X-ray diffraction results confirmed the high crystallinity of the films, with single phase nature of the ZnO and GNPs. Scanning electron microscopy micrograph analysis confirmed that the morphology of structures containing both GNPs and ZnO is influenced by the bottom layer. Diffuse reflectance spectroscopy results also indicated that the position of GNPs relative to ZnO affects the plasmon resonance of GNPs as well as the overall optical properties of the TFHSs. Photoluminescence studies revealed that the presence of GNPs affects the defect concentration in the TFHSs. The I–V characteristics showed that the TFHSs where ZnO contains GNPs in embedded form are better suited for photodiode application. This study adds a new dimension to the research on optoelectronics devices.

Single crystalline ZnO and TiO₂ nanorods are grown on fluorine-doped tin oxide (FTO) substrates by hydrothermal method. The nanorods are annealed under air and reducing conditions to alter the oxygen nonstoichiometry and hence the mid-bandgap defect states. Such an annealing process is shown to impart significant change on the photoelectrochemical (PEC) performance of the photoelectrodes. Large photocurrent densities (J) of 0.78 mA cm⁻² are obtained for air annealed (AA) TiO₂ nanorods (TNR) compared to hydrogen annealed (HA) TNR (J = 0.36 mA cm⁻²). ZnO nanorods (ZNR), on the contrary, shows photocurrent density of 0.76 mA cm⁻² and 0.36 mA cm⁻² for ZNR-HA and ZNR-AA photoanodes, respectively. The contrasting difference in the PEC performance is attributed to the synergetic effect of interfacial impedance with electrolytes and the oxygen nonstoichiometry. Further, to overcome the limitation of light absorption by these materials owing to their wide bandgap, TiO₂ and ZnO nanorods are coated with Sb₂S₃ by chemical bath deposition to form heterostructured TNR-AA/Sb₂S₃(CBD) and ZNR-HA/Sb₂S₃(CBD) thin films. Such heterostructures exhibit enhanced photocurrent values of ∼1.39 mA cm⁻² and 3.36 mA cm⁻² (at 1.6 V versus Ag/AgCl), respectively. The PEC performances of the nanorods are analyzed in terms of the annealing conditions and subsequent introduction of defect states in the bandgap. The present study shows the importance of oxygen defect control at the interface between the oxide and chalcogenide, and its role in the betterment of PEC performance in TiO₂/Sb₂S₃ and ZnO/Sb₂S₃ heterostructure photoanodes.