Towards Room Temperature Thermochromic Coatings with controllable NIR-IR modulation for solar heat management & smart windows applications

Solar heat management & green air-conditioning are among the major technologies that could mitigate heat islands phenomenon while minimizing significantly the CO2 global foot-print within the building & automotive sectors. Chromogenic materials in general, and thermochromic smart coatings especially are promising candidates that consent a noteworthy dynamic solar radiation Infrared (NIR-IR) regulation and hence an efficient solar heat management especially with the expected increase of the global seasonal temperature. Within this contribution, two major challenging bottlenecks in vanadium oxide based smart coatings were addressed. It is validated for the first time that the NIR-IR modulation of the optical transmission (∆TTRANS = T(T〈TMIT) - T(T〉TMIT) of Vanadium oxide based smart coatings can be controlled & tuned. This upmost challenging bottle-neck controllability/tunability is confirmed via a genuine approach alongside to a simultaneous drastic reduction of the phase transition temperature TMIT from 68.8 °C to nearly room temperature. More precisely, a substantial thermochromism in multilayered V2O5/V/V2O5 stacks equivalent to that of standard pure VO2 thin films but with a far lower transition temperature, is reported. Such a multilayered V2O5/V/V2O5 thermochromic system exhibited a net control & tunability of the optical transmission modulation in the NIR-IR (∆TTRANS) via the nano-scaled thickness' control of the intermediate Vanadium layer. In addition, the control of ∆TTRANS is accompanied by a tremendous diminution of the thermochromic transition temperature from the elevated bulk value of 68.8 °C to the range of 27.5-37.5 ºC. The observed remarkable and reversible thermochromism in such multilayered nano-scaled system of V2O5/V/V2O5 is likely to be ascribed to a noteworthy interfacial diffusion, and an indirect doping by alkaline ions diffusing from the borosilicate substrate. It is hoped that the current findings would contribute in advancing thermochromic smart window technology and their applications for solar heat management in glass windows in general, skyscraper especially & in the automotive industry. If so, this would open a path to a sustainable green air-conditioning with zero-energy input.

Fabrication of high performance based deep-blue OLED with benzodioxin-6-amine-styryl-triphenylamine and carbazole hosts as electroluminescent materials

The present study reports synthesis of phenathroimidazole derivatives structures following donor-acceptor relation for high performance deep-blue light emitting diodes. Herein, methyl substituted benzodioxin-6-amine phenanthroimidazoles Cz-SBDPI and TPA-SBDPI derivatives that provide the blue light were designed and synthesized. These Cz-SBDPI and TPA-SBDPI show higher glass transition (Tg) temperatures of 199 and 194 °C and demonstrate enhanced thermal properties. Apart from enhanced thermal stability these compounds also exhibit superior photophysical, electrochemical and electroluminescent properties. The non-doped carbazole based device display improved electroluminescent performances than those of TPA-based devices. The strong orbital-coupling due to decreased energy barrier between Cz-SBDPI transitions result in deep blue emission with CIE-0.15, 0.06. For non-doped Cz-SBDPI device; high L (brightness):12,984 cd/m2; ηc (current efficiency): 5.9 cd/A; ηp (power efficiency): 5.7 lm/W and ηex (external quantum efficiency): 6.2% was observed. The results show that the D-A emitters can serve as simple but also as an effective approach to devise cheap electroluminescent materials that has high efficiency and can serve as OLED devices.

Room temperature bio-engineered multifunctional carbonates for CO2 sequestration and valorization

This contribution reports, for the first time, on an entirely green bio-engineering approach for the biosynthesis of single phase crystalline 1-D nano-scaled calcite CaCO3. This was validated using H2O as the universal solvent and natural extract of Hyphaene thebaica fruit as an effective chelating agent. In this room temperature green process, CaCl2 and CO2 are used as the unique source of Ca and CO3 respectively in view of forming nano-scaled CaCO3 with a significant shape anisotropy and an elevated surface to volume ratio. In terms of novelty, and relatively to the reported scientific and patented literature in relation to the fabrication of CaCO3 by green nano-chemistry, the current cost effective room temperature green process can be singled out as per the following specificities: only water as universal solvent is used, No additional base or acid chemicals for pH control, No additional catalyst, No critical or supercritical CO2 usage conditions, Only natural extract of thebaica as a green effective chelating agent through its phytochemicals and proper enzematic compounds, room Temperature processing, atmospheric pressure processing, Nanoscaled size particles, and Nanoparticles with a significant shape anisotropy (1-D like nanoparticles). Beyond and in addition to the validation of the 1-D synthesis aspect, the bio-engineered CaCO3 exhibited a wide-ranging functionalities in terms of highly reflecting pigment, an effective nanofertilizer as well as a potential binder in cement industry.

Extraction of Natural Pigment Curcumin from Curcuma Longa: Spectral, DFT, Third-order Nonlinear Optical and Optical Limiting Study

Herein, we report the extraction of natural pigment curcumin from curcuma longa and their linear and third-order nonlinear optical (NLO) characteristics. The characterization techniques viz., UV-Visible absorption, FT-IR, Micro Raman and Gas Chromatography Mass Spectrum (GC-MS) are used to study the spectral characteristics of curcumin. Third-order NLO features of curcumin are studied using Z‒scan technique with a semiconductor diode laser working at 405 nm wavelength. The natural pigment exhibits negative nonlinear index of refraction resulting from self-defocusing and positive coefficient of absorption is the consequence of reverse saturable absorption (RSA). The order of nonlinear index of refraction (n2) and nonlinear coefficient of absorption (β) is measured to be 10-7 cm2/W and 10-2 cm/W, respectively. Third-order NLO susceptibility (χ(3)) and second-order hyperpolarizability (γ) of curcumin is measured to be 2.73 × 10‒7 esu and 1.67 × 10‒31 esu, respectively. A low optical limiting (OL) threshold of 0.71 mW is observed in the extracted pigment. The experimental results are supplemented by quantum mechanical calculations of the NLO parameters. The overall result finding is that curcumin extracted from curcuma longa has the potential to be novel optical candidates for photonics and optoelectronics applications.

A computational study of the thortveitite structure of zinc pyrovanadate, Zn2V2O7, under pressure

We performed a pressure-driven study of zinc pyrovanadate, Zn₂V₂O₇, using the first-principles approach under the framework of density functional theory (DFT). Zn₂V₂O₇ crystalizes in a monoclinic (α-phase) structure with the space group C2/c at ambient pressure. In comparison with the ambient phase, there are four different high-pressure phases, namely β, γ, κ and δ, found at 0.7, 3.8, 4.8 and 5.3 GPa, respectively. The detailed crystallographic analysis as well as their structures is consistent with the theory and experiment reported in the literature. All phases including the ambient phase are mechanically stable, elastically anisotropic and malleable. The compressibility of the studied pyrovanadate is higher than that of the other meta- and pyrovanadates. The energy dispersion of these studied phases reveals that they are indirect band gap semiconductors with wide band gap energies. The band gap energies follow a reduced trend with pressure except the κ-phase. The effective masses for all of these studied phases were computed from their corresponding band structures. The values of energy gaps obtained from the band structures are almost similar to the optical band gap obtained from the optical absorption spectra, as estimated by the Wood-Tauc theory.

On the trapping of neutrons in Fabry–Pérot nano-structures and potential applications for cold neutron lifetime Investigations

Correlated to the neutron total reflection phenomenon is the so-called frustrated total reflection, also known as neutron channeling, observed with both thermal and cold neutrons. Within this contribution, such a phenomenon is validated in various additional distinctive Fabry–Pérot nano-resonating configurations; namely in: (i) dual reflection and transmission neutron Fabry–Pérot nano-resonator (Ni/V/Ni/Si substrate), (ii) isotope-based neutron Fabry–Pérot nano-resonator (58Ni/62Ni/58Ni/Silicon substrate), and (iii) multilayered neutron Fabry–Pérot nano-resonator of 8 superposed (B4C/Ti/B4C) single nano-resonators. While such Fabry–Pérot nano-resonators allow effective neutron trapping, the precision of the trapping time of free neutrons in such nano-resonators is governed by the Heisenberg uncertainty and hence offers, a priori, an additional attractive precise approach for potential lifetime investigations. Depending on the configuration of the Fabry–Pérot nano-resonators and the available cold neutron beam, the trapping time is found to be within the temporal regime of 3 to 19 ps. While the main intention of this contribution is to validate the possibility of trapping cold neutrons in nano-structured Fabry–Pérot resonators with a picosecond precision in various configurations, it is hoped that these preliminary results will attract the interest of the neutron lifetime community specifically and the neutron scattering community in general. The potential integration of such trapping method into the bottle or beam methods would elucidate the origin of the difference in neutron lifetime between the two approaches.

Physical properties of computationally informed phyto-engineered 2-D nanoscaled hydronium jarosite

This study describes a molecular dynamics computational modelling informed bioengineering of nano-scaled 2-D hydronium jarosite. More specifically, a phyto-engineering approach using green nano-chemistry and agro-waste in the form of avocado seed natural extract was utilized as a green, economic, and eco-friendly approach to synthesize this unique mineral at the nanoscale via the reduction of iron (II) sulphate heptahydrate. The nanoproduct which was found to exhibit a quasi-2D structure was characterized using a multi-technique approach to describe its morphological, optical, electrochemical, and magnetic properties. Radial distribution function and electrostatic potential maps revealed that flavone, a phenolic compound within the avocado seed natural extract, has a higher affinity of interaction with the nanoparticle's surface, whilst vanillic acid has a higher wetting tendency and thus a lower affinity for interacting with the hydronium jarosite nanoparticle surface compared to other phytoactive compounds. XRD and HRTEM results indicated that the nanoscale product was representative of crystalline rhombohedral hydronium jarosite in the form of quasi-triangular nanosheets decorated on the edges with nanoparticles of approximately 5.4 nm diameter that exhibited significant electrochemical and electroconductive behaviours. Magnetic studies further showed a diamagnetic behaviour based on the relationship of the inverse susceptibility of the nanomaterial with temperature sweep.

Reproducibility and long-term stability of Sn doped MnO2 nanostructures: Practical photocatalytic systems and wastewater treatment applications

Sn-doped MnO₂ were synthesized as an oxidant, a mediator of maleic acid (C₄H₄O₄) and SnCl₂ as doping ingredient via a basic sol-gel reaction with KMnO₄. XRD study signposts that tetragonal crystal structure of MnO₂ (ICDD#44-0141) with a plane group of 12/m (87) for both pure and Sn doped MnO₂ nanostructures. The photocatalyst synthesized has mesoporosity, allowing to the N₂ adsorption/desorption experiments. The geometry of the materials varies from spherical shape in pristine MnO₂ to a rod-like shape in Sn-MnO₂, as observed in the SEM and TEM pictures. To examine optic properties and energy bandgaps topologies, UV-visible diffuse reflectance spectroscopy was applied. In visible spectrum, overall catalytic performance of Sn-doped MnO₂ was tested using methyl orange and phenol as dyes. The results suggest that the optimized Sn doped MnO₂ (10 wt.%) catalyst showed higher degradation efficiency (98.5%), apparent constant (0.7841 min^-1) and long term permanence. For this improved charge extraction efficiency, a potential photocatalytic mechanism was proposed.

Mercury goes Solid at room temperature at nanoscale and a potential Hg waste storage

While room temperature bulk mercury is liquid, it is solid in its nano-configuration (Ønano-Hg ≤ 2.5 nm). Conjugating the nano-scale size effect and the Laplace driven surface excess pressure, Hg nanoparticles of Ønano-Hg ≤ 2.4 nm embedded in a 2-D turbostratic Boron Nitride (BN) host matrix exhibited a net crystallization at room temperature via the experimentally observed (101) and (003) diffraction Bragg peaks of the solid Hg rhombohedral α-phase. The observed crystallization is correlated to a surface atomic ordering of 7 to 8 reticular atomic plans of the rhombohedral α-phase. Such a novelty of size effect on phase transition phenomena in Hg is conjugated to a potential Hg waste storage technology. Considering the vapor pressure of bulk Hg, Room Temperature (RT) Solid nano-Hg confinement could represent a potential green approach of Hg waste storage derived from modern halogen efficient light technology.

From Khoi-San indigenous knowledge to bioengineered CeO2 nanocrystals to exceptional UV-blocking green nanocosmetics

Single phase CeO₂ nanocrystals were bio-synthesized using Hoodia gordonii natural extract as an effective chelating agent. The nanocrystals with an average diameter of 〈Ø〉 ~ 5-26 nm with 4⁺ electronic valence of Ce displayed a remarkable UV selectivity and an exceptional photostability. The diffuse reflectivity profile of such CeO₂ exhibited a unique UV selectivity, in a form of a Heaviside function-like type profile in the solar spectrum. While the UV reflectivity is significantly low; within the range of 0.7%, it reaches 63% in the VIS and NIR. Their relative Reactive Oxygen Species (ROS) production was found to be < 1 within a wide range of concentration (0.5-1000 μg/ml). This exceptional photostability conjugated to a sound UV selectivity opens a potential horizon to a novel family of green nano-cosmetics by green nano-processing.

From Himba indigenous knowledge to engineered Fe2O3 UV-blocking green nanocosmetics

This contribution reports on the physical properties of the natural Namibian red Ochre used by the Himba Community in a form of a formulation, so called Otjize as a skin protective and beauty cream. The morphological and crystallographic studies of this red ochre validated its nano-scaled dominating phase of rhombohedral α-Fe₂O₃ nanocrystals with an additional hydrolized oxide component in a form of γ-FeOOH. The optical investigations showed that such a red ochre exhibits an exceptional UV filtration and a significant IR reflectivity substantiating its effectiveness as an effective UV-blocking & solar heat IR reflector in support of the low skin cancer rate within the Namibian Himba community. In addition, such nanocrystals exhibited a non-negligible antibacterial response against E. Coli & S. Aurus. This study seems confirming the effectiveness of the indigenous Otjize as an effective skin UV protection cream with a sound antimicrobial efficacy against e-Coli & S-Aurus.

Studies on the spectrometric analysis of metallic silver nanoparticles (Ag NPs) using Basella alba leaf for the antibacterial activities

In this present investigation, an aqueous Basella alba leaves extract was used to synthesize AgNPs. The green synthesis approach is carried out in our work due to non-toxic, less cost, and ecofriendly methods. FTIR spectra are used to confirm the biomolecules present in B.alba leaves extract along with AgNPs and these compounds are responsible for Ag particle from micro to nanostructure. The FCC structure and crystalline nature of the AgNPs are analyzed with the help of XRD and TEM techniques respectively. DLS and Zeta potential techniques are carried out to find the size and stability of AgNPs respectively and UV is used to verify the presence of AgNPs in synthesized samples employing SPR peaks around 435 nm. The antioxidant studies expose eminent scavenging activity which ranges from 13.71% to maximum 67.88%. Green synthesized AgNPs possess well organized biological activities concerning antioxidant and antibacterial, which can be used in some biologically applications.

CdO/CdCO3 nanocomposite physical properties and cytotoxicity against selected breast cancer cell lines

Cadmium Oxide nanoparticles have the lowest toxicity when compared to nanoparticles of other semiconductors and they are not detrimental to human and mammalian cells, thereby making them candidates for targeting cancer cells. Synadenium cupulare plant extracts were used to synthesize CdO/CdCO3 nanocomposite using cadmium nitrate tetrahydrate 98% as a precursor salt. The resultant nanoparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The nanoparticles were then screened for effect on breast cancer cell lines (MCF-7 and MDA MB-231) and Vero cell line to determine their growth inhibition effect. Cytotoxicity effect was evaluated using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. XRD showed the peaks of monteponite CdO and otavite CdCO3 nanoparticles. TEM results showed irregular and spherical particles of varying sizes, whilst SEM revealed a non-uniform morphology. FTIR results showed peaks of functional groups which are present in some of the phytochemical compounds found in S. cupulare, and point to the presence of CdO. Annealed CdO/CdCO3 NPs showed selectivity for MCF7 and MDA MB231 in comparison to Vero cell line, thereby supporting the hypothesis that cadmium oxide nanoparticles inhibit growth of cancerous cells more than non-cancerous cells.

VO2-based active tunable emittance thermochromic flexible coatings

This contribution reports, for what we believe is the first time, on VO₂-based thin-film coatings on flexible Al substrates exhibiting a tunable positive emittance-switching Δε=(ε_H-ε_L)>0. More precisely, a layered stack of a-Si:H/SiO₂/VO₂ on flexible Al sheets presents minimum and maximum values of emissivity of about 0.18 and 0.57 at 40ºC and 83ºC, respectively, and hence allows an emittance-switching Δε of 0.39 and a relative variation Δε/ε_Λ of ∼217%. Such variations fit with the potential applications of such coatings as smart radiation devices in small satellites and spacecraft.

Anderson localization of IR light in 1D nanosystems

This contribution reports on the observation of a strong light localization of Anderson type in 1D systems consisting of ship-shaped carbon nanotubes. Such a localization of infrared (IR) light was observed using Fourier transform infrared spectroscopy under attenuated total reflection geometry within the spectral range of 2-20 µm. Such an IR light localization manifests itself in the form of a significant interference profile of the optical transmission over the full wavenumber range of 400-4000cm^-1.

Optical properties of biosynthesized nanoscaled Eu2O3 for red luminescence applications

This contribution reports on the optical properties of biosynthesised Eu₂O₃ nanoparticles bioengineered for the first time by a green and cost effective method using aqueous fruit extracts of Hyphaene thebaica as an effective chelating and capping agent. The morphological, structural, and optical properties of the samples annealed at 500°C were confirmed by using a high-resolution transmission electron microscope (HR-TEM), x-ray diffraction analysis (XRD), UV-Vis spectrocopy, and photoluminescence spectrometer. The XRD results confirmed the characteristic body-centered cubic (bcc) structure of Eu₂O₃ nanoparticles with an average size of 20 nm. HR-TEM revealed square type morphology with an average size of ∼6nm. Electron dispersion energy dispersive x-ray spectroscopy spectrum confirmed the elemental single phase nature of pure Eu₂O₃. Furthuremore, the Fourier transformed infrared spectroscopy revealed the intrinsic characteristic peaks of Eu-O bond stretching vibrations. UV-Vis reflectance proved that Eu₂O₃ absorbs in a wide range of the solar spectrum from the VUV-UV region with a bandgap of 5.1 eV. The luminescence properties of such cubic structures were characterized by an intense red emission centered at 614 nm. It was observed that the biosynthesized Eu₂O₃ nanoparticles exhibit an efficient red-luminescence and hence a potential material as red phosphor.

Thermal conductivity enhancement in gold decorated graphene nanosheets in ethylene glycol based nanofluid

We report on the synthesis and thermal conductivity of gold nanoparticles (AuNPs) decorated graphene nanosheets (GNs) based nanofluids. The GNs-AuNPs nanocomposites were synthesised using a nanosecond pulsed Nd:YAG laser (wavelength = 1,064 nm) to ablate graphite target followed by Au in ethylene glycol (EG) base fluid to obtain GNs-AuNPs/EG hybrid nanofluid. The characterization of the as-synthesised GNs-AuNPs/EG hybrid nanofluid confirmed a sheet-like structure of GNs decorated with crystalline AuNPs with an average particle diameter of 6.3 nm. Moreover, the AuNPs appear smaller in the presence of GNs which shows the advantage of ablating AuNPs in GNs/EG. The thermal conductivity analysis in the temperature range 25-45 °C showed that GNs-AuNPs/EG hybrid nanofluid exhibits an enhanced thermal conductivity of 0.41 W/mK compared to GNs/EG (0.35 W/mK) and AuNPs/EG (0.39 W/mK) nanofluids, and EG base fluid (0.33 W/mK). GNs-AuNPs/EG hybrid nanofluid displays superior enhancement in thermal conductivity of up to 26% and this is due to the synergistic effect between AuNPs and graphene sheets which have inherent high thermal conductivities. GNs-AgNPs/EG hybrid nanofluid has the potential to impact on enhanced heat transfer technological applications. Also, this work presents a green synthesis method to produce graphene-metal nanocomposites for various applications.

Remarkable thermal conductivity enhancement in Ag-decorated graphene nanocomposites based nanofluid by laser liquid solid interaction in ethylene glycol

We report on the synthesis and enhanced thermal conductivity of stable Ag-decorated 2-D graphene nanocomposite in ethylene glycol based nanofluid by laser liquid solid interaction. A surfactant free nanofluid of Ag nanoparticles anchored onto the 2-D graphene sheets were synthesized using a two-step laser liquid solid interaction approach. In order to understand a pulsed Nd:YAG laser at the fundamental frequency (λ = 1,064 nm) to ablate Ag and graphite composite target submerged in ethylene glycol (EG) to form AgNPs decorated 2-D GNs-EG based nanofluid. From a heat transfer point of view, it was observed that the thermal conductivity of this stable Ag-graphene/EG is significantly enhanced by a factor of about 32.3%; this is highest reported value for a graphene based nanofluid.

Performance of various cyanide degrading bacteria on the biodegradation of free cyanide in water

This study reports on the biodegradation of free cyanide (FCN) by cyanide degrading bacteria (CDB) that were isolated from mining wastewater and thiocyanate containing wastewater. The performance of these isolates was compared to cryopreserved CDBs that were used in previous studies. The performance of the isolates to degrade FCN was studied in batch cultures. It was observed that the CDB from the thiocyanate wastewater showed higher biodegradation rates (2.114 g CN^-. L^-1.O.D_600 nm^-1.h^-1) compared to the isolates from the mining wastewater. The isolates from the cryopreserved CDBs and from the mining wastewater achieved a biodegradation rate of 1.285 g CN^- L^-1.O.D_600 nm^-1.h^-1 and 1.209 g CN^-.L^-1.O.D_600 nm^-1.h^-1, respectively. This study demonstrated that the source of the organisms plays a significant role on FCN biodegradation.

Up-Scalable Synthesis of Size-Controlled White-Green Emitting Behavior of Core/Shell (CdSe/ZnS) Quantum Dots for LED Applications

Research on CdSe/ZnS core-shell quantum dots (QDs) was synthesized by a chemical route using bio-conjugated organic amino acid (L-Cysteine). The structural, morphological, and optical properties of the nanocrystal powder samples were analyzed using various characterization techniques. The diameter of the resulting QDs was about 3 nm with uniform size distribution. The optical properties QDs exhibited an absorption and emission peak at 515 and 525 nm respectively, at room temperature. The QDs through emission in the spectral range at 516-535 nm is special for their application in green LEDs and white-light generation. The high optical properties performance of the QDs nanocomposites gained indicates that the materials are promising for (LED) applications.

Antioxidant and Photocatalytic Activity of Aqueous Leaf Extract Mediated Green Synthesis of Silver Nanoparticles Using Passiflora edulis f. flavicarpa

The purpose of this study is to minimize the negative impacts of synthetic procedures and to develop environmentally benign procedures for the synthesis of metallic nanoparticles. In the present study, Passiflora edulis f. flavicarpa (P. edulis) aqueous leaf extract mediated green synthesis of silver nanoparticles are described. The synthesized silver nanoparticles were characterized by UV-Vis Spectroscopy, Fluorescence Spectroscopy, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) Transmission Electron Microscopy (TEM) and Cyclic Voltammetry (CV). The silver nanoparticles (AgNPs) showed antibacterial activities against both gram positive (staphylococcus) and gram negative (Escherichia coli) bacteria. The efficacy of the synthesized silver nanoparticles (AgNPs) was demonstrated as catalyst in the photocatalytic degradation of Methyl Orange (MO) and Methylene Blue (MB) dyes which were measured spectrophotometrically. The study revealed that biosynthesized silver nanoparticles using Passiflora. edulis f. flavicarpa, plant extract was found to be very effective as antioxidant agent.

Photocatalytic Activity and Humidity Sensor Studies of Magnetically Reusable FeWO₄-WO₃ Composite Nanoparticles

Different mole ratios of (8:2, 6:4, 4:6 and 2:8) iron tungstate-tungsten trioxide (FeWO₄-WO₃) composite nanoparticles were synthesized by solid state method. The synthesized composite nanoparticles were characterized by powder X-ray diffraction analysis (XRD), field-emission scanning electron microscopy (FE-SEM) with energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) studies. The crystalline nature and particle size of the samples were characterized by powder X-ray diffraction analysis (XRD). The morphology was confirmed by field-emission scanning electron microscopy (FE-SEM) analysis and transmission electron microscope (TEM). The energy dispersive X-ray spectroscopy (EDX) proved the purity of nanocomposites. Vibrating sample magnetometer reveals that the sample shows paramagnetic property based on the metal present in the prepared nanocomposites at room temperature. The magnetic property is due to the structural defects rather than the impurity phase. Magnetization saturation value (M_s = 398.7 emu/g) of FWWO-46 composite nanoparticles is high enough to be magnetically removed by applying a magnetic field. The composites were subjected to DC conductance measurement as a function of relative humidity in the range of 5-98%, achieved by different water vapour buffers thermostated at room temperature. The sensitivity factor, S_f (R_5%/R_98%) measured at 25 °C revealed that FWWO-46 shows the highest humidity sensitivity factor S_f = 3956, with a response and recovery time of 45 s and 100 s respectively. Photocatalytic degradation of methylene blue (MB) from aqueous solution has been carried out using FeWO₄-WO₃ composite nanoparticles as photocatalyst under Ultraviolet radiation.

Optical, Magnetic and Photocatalytic Activity Studies of Li, Mg and Sr Doped and Undoped Zinc Oxide Nanoparticles

Nanoparticles of Li, Mg and Sr doped and undoped zinc oxide was prepared by simple precipitation method. The structural, optical, and magnetic properties of the samples were investigated by the Powder X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared (FTIR) spectroscopy, Ultra-violet Visible spectroscopy (UV-vis) spectra, Photoluminescence (PL) and Vibrational Sample Magnetometer (VSM). The Powder X-ray diffraction data confirm the formation of hexagonal wurtzite structure of all doped and undoped ZnO. The SEM photograph reveals that the pores availability and particles size in the range of 10 nm-50 nm. FTIR and UV-Visible spectra results confirm the incorporation of the dopant into the ZnO lattice nanostructure. The UV-Visible spectra indicate that the shift of blue region (lower wavelength) due to bandgap widening. Photoluminescence intensity varies with doping due to the increase of oxygen vacancies in prepared ZnO. The pure ZnO exist paramagnetic while doped (Li, Mg and Sr) ZnO exist ferromagnetic property. The photocatalytic activity of the prepared sample also carried out in detail.

Direct Electrodeposition of Gold Nanoparticles on Glassy Carbon Electrode for Selective Determination Catechol in the Presence of Hydroquinone

A simple and reliable voltammetric sensor for simultaneous determination of Catechol (CT) and Hydroquinone (HQ) was developed by electrodepositing the gold nanoparticles on the surface of the Glassy Carbon Electrode (GCE). The cyclic voltammograms in a mixed solution of CT and HQ have shown that the oxidation peaks become well resolved and were separated by 110 mV, although the bare GCE gave a single broad oxidation peak. Moreover, the oxidation peak currents of both CT and HQ were remarkably increased three times in comparison with the bare GCE. This makes gold nanoparticles deposited GCE a suitable candidate for the determination of these isomers. In the presence of 1 mM HQ isomer, the oxidation peak currents of differential pulse voltammograms are proportional to the concentration of CT in the range of 21 μM to 323 μM with limit of detection 3.0 μM (S/N = 3). The proposed sensor has some important advantages such as low cost, ease of preparation, good stability and high reproducibility.

Photocatalytic decomposition effect of erbium doped cerium oxide nanostructures driven by visible light irradiation: Investigation of cytotoxicity, antibacterial growth inhibition using catalyst

Cerium (IV) oxide (CeO₂) is the most accessible noble rare earth metal oxide for the excitation of the excitons by light-harvesting performance. The present work is focused on Erbium doped ceria nanoparticles that were beneficially obtained by hydrothermal method from cerium nitrate and Erbium nitrate as precursors for decomposition of Rhodamine-B (RhB) dye in the polluted waste water removed from the industries. Dye removal efficiency of the catalyst was found to be nearly ~94%. The structural phases, functional groups and the transitions are identified with the help of various techniques. XRD pattern determines the development of cubic phase with the particle size is 20 nm. Highly crystalline nature of as-synthesized nanomaterials with an average diameter of 35 nm was investigated by HRSEM. The crystalline size, shape and textural morphology, of the Erbium doped ceria nanostructures were analysed by HRTEM. Our results suggest, that the concentration of OH- ion determines the lattice constants and oxygen vacancy in the nanostructures which stimulate the probability of photocatalytic decomposition effect of organic pollutants, due to synergistic approach. In this context, both unhydrolyzed things and their swiftly drip from deceased or scratched cells with conceded membranes, even when the cells embrace some are outstanding attention. Although, the loss of viable cells also depends on epithelial cell dynamically conceal of numerous molar matrix.

Structural, Optical, Morphological and Microbial Studies on SnO₂ Nanoparticles Prepared by Co-Precipitation Method

Nanoparticles of tin oxide (SnO2) powders were prepared by co-precipitation method at 500 °C, 700 °C and 900 °C temperature. The sintered SnO2 nanoparticles, structural, optical, magnetic, morphological properties and microbial activity have been studied. XRD studies reveals that sintered powder which exhibits tetragonal crystal structure and both crystallinity as well as crystal size increase with increase in temperature. The morphological studies reveal randomly arranged grains with compact nature grain size increases with sintering temperature. The compositional analyses of SnO2 nanoparticles have been studied using X-ray photoelectron spectroscopy analysis. The optical band gap values of SnO2 nanoparticles were calculated to be about 4.3 eV in the temperature 500 °C, comparing with that of the bulk SnO2 3.78 eV, by optical absorption measurement. Room temperature M-H curve for pure SnO2 nanoparticles exhibits ferromagnetic behaviour. The tin oxide nanoparticles are acted as potential candidate material for bacterial and fungal activity.

Large-scale synthesis of coiled-like shaped carbon nanotubes using bi-metal catalyst

Carbon nanomaterials (CNMs), especially carbon nanotubes (CNTs) with coiled structure exhibit scientifically fascinating. They may be projected as an innovative preference to future technological materials. Coiled carbon nanotubes (c-CNTs) on a large-scale were successfully synthesized with the help of bi-metal substituted α-alumina nanoparticles catalyst via chemical vapor deposition (CVD) technique. Highly spring-like carbon nanostructures were observed by field emission scanning electron microscope (FESEM) examination. Furthermore, the obtained material has high purity, which correlates the X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) analysis. Raman spectroscopy reveals that the carbon multi layers are well graphitized and crystalline, even if they have defects in its structure due to coiled morphology. High-resolution transmission electron microscope (HRTEM) describes internal structure and dia of the product. Ultimately, results support the activity of bi-metal impregnated α-alumina nanoparticles catalyst to determine the high yield, graphitization and internal structure of the material. We have also studied the purified c-CNTs magnetic properties at room temperature and will be an added advantage in several applications.

Theoretical study of electromagnetic transport in Lepidoptera Danaus plexippus wing scales

This paper examines the electromagnetic energies developed in the scales of the Lepidoptera Danaus plexippus. The Green tensor method was used to calculate and simulate the energies at specific wavelengths. Scattering of electromagnetic waves within the scales was simulated at different wavelengths (λ) with the corresponding maximum energy occurred at λ = 0.45 μm. The study shows that the design of wing’s cross-ribs maximizes the eigenmode of electromagnetic energy. This shows promising applications in bio-sensors of Solar light and likewise in waveguide for photonic transmission.

Bioreduction potentials of dried root of Zingiber officinale for a simple green synthesis of silver nanoparticles: Antibacterial studies

Green synthesis of silver nanoparticles (Ag NPs) using an extract of dried Zingiber officinale (ginger) root as a reducing and capping agent in the presence of microwave irradiation was herein reported for the first time. The formation of symmetrical spheres is confirmed from the UV-Visible spectrum of Ag NPs. Fourier transform infra-red spectroscopy confirms the formation of the Ag NPs. X-ray diffraction analysis was utilized to calculate the crystallite size of Ag NPs and the value was found to be 10nm. High-resolution transmission electron microscopy and high-resolution scanning electron microscopy were used to investigate the morphology and size of the synthesized samples. The sphere like morphology is confirmed from the images. The purity and crystallinity of Ag NPs is confirmed by energy-dispersive X-Ray analysis and selected area electron diffraction respectively. The electrochemical behavior of the synthesized Ag NPs was assessed by cyclic voltammetry (CV) and shows the redox peaks in the potential range of -1.1 to +1.1V. Agar diffusion method is used to examine the antibacterial activity of Ag NPs. For this purpose, two gram positive and two gram negative bacteria were studied. This single step approach was found to be simple, short time, cost-effective, reproducible, and eco-friendly.

Elucidation of photocatalysis, photoluminescence and antibacterial studies of ZnO thin films by spin coating method

The ZnO thin films have been prepared by spin coating followed by annealing at different temperatures like 300°C, 350°C, 400°C, 450°C, 500°C & 550°C and ZnO nanoparticles have been used for photocatalytic and antibacterial applications. The morphological investigation and phase analysis of synthesized thin films well characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Photoluminescence (PL), Transmission Electron Microscopy (TEM) and Raman studies. The luminescence peaks detected in the noticeable region between 350nm to 550nm for all synthesized nanosamples are associated to the existence of defects of oxygen sites. The luminescence emission bands are observed at 487nm (blue emission), and 530nm (green emission) at the RT. It is observed that there are no modification positions of PL peaks in all ZnO nanoparticles. In the current attempt, the synthesized ZnO particles have been used photocatalytic and antibacterial applications. The antibacterial activity of characterized samples was regulated using different concentrations of synthesized ZnO particles (100μg/ml, 200μg/ml, 300μg/ml, 400μg/ml, 500μg/ml and 600μg/ml) against gram positive and gram negative bacteria (S. pnemoniae, S. aureus, E. coli and E. hermannii) using agar well diffusion assay. The increase in concentration, decrease in zone of inhibition. The prepared ZnO morphologies showed photocatalytic activity under the sunlight enhancing the degradation rate of Rhodamine-B (RhB), which is one of the common water pollutant released by textile and paper industries.