E-waste refers to discarded electronic refuse that originates from various sources, posing severe environmental and health risks due to its harmful components. This chapter focuses on IoT-enabled solutions for E-waste monitoring and recycling, highlighting the importance of creative solutions. Due to its harmful components, electronic trash (also known as E-waste), defined as discarded electronic gadgets, poses serious environmental and health dangers. This chapter explains E-waste's causes, difficulties, and mitigation tactics while highlighting the significance of creative solutions. The Internet of Things (IoT) is a game-changing strategy for managing E-waste, facilitating real-time monitoring and data collection for effective accumulation tracking, improved collection routes, and data-driven resource allocation decisions. This chapter introduces the conceptual design for a Smart Bin system, describing how IoT devices can facilitate real-time monitoring and data aggregation for E-waste collection and recycling. The deployment of a Smart Bin system that rewards users for active involvement is crucial and encourages user engagement, revolutionizing E-waste management with IoT-enabled technologies and smart bin approaches. The chapter serves as an excellent illustration of how technology can play a crucial role in easing the E-waste situation, encouraging sustainability, and producing a cleaner environment for future generations.

We explored the impact of Gd doping on the structural, electronic and optical characteristics of the ZnO powder. The Gd-doped ZnO (0, 2% and 5%) powder samples have been synthesized using the conventional solid-state reaction process with varied Gd concentrations. The XRD pattern confirmed that all the studied samples are in the hexagonal wurtzite crystalline structure. The morphology has been explored using SEM images, which exhibited an agglomerated rod-like particle structure. The XPS results indicate the presence of oxygen vacancies (Vo) in the Gd-doped ZnO samples and the Vo’s are found to increase with increasing Gd amount. According to PL findings, the intensity ratio of the green and ultra-violet emission peaks is found to increase from 0.090 to 0.418 with increasing Gd-doping concentrations, confirming that Vo’s are increasing with Gd-doping. The UV-visible spectroscopy results reveal that the energy band gap (Eg) decreased from 3.31 eV to 3.23 eV with increasing Gd-doping concentration. Bangladesh J. Sci. Ind. Res. 58(1), 53-64, 2023

The different dyes used and discharged in industrial settings and microbial pathogenic issues have raised serious concerns about the content of bodies of water and the impact that dyes and microbes have on the environment and human health.

Zinc oxide is a multifunctional material with important applications in areas like electronics, optoelectronics, sensors and photocatalysis. In the present work, the Cu-doped ZnO (Cu = 0%, 2% and 5%) nanoparticles have been synthesized and investigated using various techniques like XRD, SEM, XPS, PL and UV spectroscopic measurements. The study is aimed at exploring the mechanism of room-temperature ferromagnetism in these dilute magnetic semiconductors, which has been a mystery for a long time. The X-ray diffraction patterns revealed the hexagonal wurtzite crystal structure of the P6 3 mc space group and an average crystalline size of 26 nm to 32 nm. The morphology has been analyzed using SEM images, which depict irregular grain size distribution and agglomerated spheroid-like particle structure. The X-ray photoelectron spectroscopy (XPS) findings exhibited the inducement of remarkable oxygen vacancies (V o ) with Cu doping. The 2% Cu-doped sample shows the maximum value of the oxygen vacancies. The magnetization measurements reveal weak ferromagnetism in the pure ZnO sample, whereas the Cu-doped ZnO nanocrystalline samples show remarkable room temperature ferromagnetism (RTFM). The 2% Cu-doped sample depicts the highest value of saturation magnetization. The UV spectroscopy indicates that the band gap is reduced upon Cu doping; the value of E g is found to be the lowest (2.96 eV) for the 2% Cu-doped sample. The Photoluminescence (PL) spectroscopy indicates the presence of defect-related states, which are found to be the maximum for the 2% Cu-doped sample, in good agreement with the XPS results. The induced magnetization in the Cu-doped nano-crystalline samples is found to show a direct relationship with the oxygen vacancies and is proposed to be caused by the exchange interactions between the Cu 2+ ions and the oxygen vacancies. The inducement of ferromagnetism in ZnO renders it a potential system for spintronic devices. The key benefits of spintronic devices are their compact size, excellent luminous efficiency, ecologically benign composition, long persistence and potential energy savings.

Polycrystalline Zn1−xCuxO (x = 0.0, 0.02, and 0.05) samples have been prepared using the solid-state reaction procedure. The X-ray diffraction (XRD) patterns of the samples confirm that Cu ions are successfully included in the ZnO hexagonal wurtzite structure. Rietveld analysis of the XRD patterns confirms the phase purity of the synthesized samples and a slight variation in their lattice parameter upon Cu doping. The morphology study by scanning electron microscopy (SEM) depicts transfiguration with Cu doping. The existence of oxygen vacancies (Vo) in the Cu-doped samples is indicated by X-ray photoelectron spectroscopy (XPS). The magnetization measurements reveal the diamagnetic nature of pure ZnO while the Cu-doped samples depict a room-temperature ferromagnetic (RTFM) behavior. The 2

The current study unravels the structural, optical band gap and magnetic characteristics of rare-earth (RE) gadolinium (Gd) substituted CoGdxFe2-xO4 (x= 0.00 - 0.10, in the interval of 0.02) nanocrystallites synthesized by the sol-gel self-ignition route. The XRD analysis and Rietveld refinement confirmed the existence of a single cubic phase with a crystallite size of ~15-21 nm range, further confirmed by HRTEM results. SEM images confirmed the well-known nano-size morphology for all the samples. The magnetization measurements show a hard ferromagnetic nature for all specimens within the temperature range of 20-300K. Coercivity, remanent, and saturation magnetization monotonically increased with a reduction in temperature from 300K to 20K. UV-Vis absorbance results show that the band gap energy of CoFe2O4 nanoparticles (NPs) decreases with increasing Gd3+ ion doping and have band gap energy values of 2.47, 2.15, 2,02, 2.00, 1.43 and 1.95 eV for x= 0.00, 0.02, 0.04, 0.06, 0.08, 0.10, respectively in CoGdxFe2-xO4 nanoferrites. The present study reveals that structural, optical band gap and magnetic properties could be altered by monitoring the quantity of gadolinium in cobalt nanoferrites. Bangladesh J. Sci. Ind. Res. 57(3), 173-186, 2022

Herein, we demonstrate a simple, reproducible, and environment-friendly strategy for the synthesis of carbon quantum dots (CQDs) utilizing the mango (Mangifera indica) kernel as a renewable green carbon source. Various analytical tools characterized the as-prepared CQDs. These fluorescent CQDs showed significant water solubility with a uniform size of about 6 nm. The as-synthesized CQDs show significantly enhanced catalytic activity for the production of α,β-unsaturated compounds from the derivatives of aromatic alkynes and aldehydes under microwave irradiation in aqueous media. A potential mechanistic pathway and role of carboxylic functionalities were also revealed via various control experiments. The protocol shows outstanding selectivity towards the assessment of α,β-unsaturated compounds over other possible products. A comparative evaluation suggested the as-synthesized CQDs show higher catalytic activity under microwave radiation as compared to the conventional ways. These recyclable CQDs represent a sustainable alternative to metals in synthetic organic chemistry. A cleaner reaction profile, low catalyst loading, economic viability and recyclability of the catalyst, atom economy, and comprehensive substrate applicability are additional benefits of the current protocol according to green chemistry.

The current article explores the dielectric and electronic properties of cobalt ferrite nanoparticles with Gd substitution in a series CoGd x Fe 2-x O 4 (0 ≤ x ≤ 0.1, in step x = 0.02) synthesized by the sol–gel self-combustion way. All the samples were studied with Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and impedance (dielectric) analyzer. One absorption band (υ 1 ) was observed in FTIR measurements, which is the characteristic feature of spinel nanoferrites in fcc type structure. The presence of active Raman modes in Raman spectra at room temperature demonstrated single phase formation of cobalt nanoferrites with metallic–metallic and metallic–oxygen bonding vibrations in the tetrahedral and octahedral sites. XPS data analysis confirmed phase purity and revealed incorporation of Gd ion in the spinel fcc lattice. The valence states of Fe, Co & Gd atoms in all these nanoparticles are found as Fe 3+ , Co 2+ , & Gd 3+ . The dielectric constant and dielectric loss are measured in a broad frequency range of 100 Hz to 120 MHz. The dielectric constant reduces with a rise in Gd concentration and frequency. This study reveals that electronic and dielectric properties could be effectively tuned by varying concentrations of gadolinium in cobalt ferrite nanoparticles.

In the present work, zinc oxide (ZnO) and silver (Ag) doped ZnO nanostructures are synthesized using a hydrothermal method. Structural quality of the products is attested using X-ray diffraction, which confirms the hexagonal wurtzite structure of pure ZnO and Ag-doped ZnO nanostructures. XRD further confirms the crystallite orientation along the c-axis, (101) plane. The field emission scanning electron microscope study reveals the change in shape of the synthesized ZnO particles from hexagonal nanoparticles to needle-shaped nanostructures for 3 wt% Ag-doped ZnO. The optical band gaps and lattice strain of nanostructures is increased significantly with the increase of doping concentration of Ag in ZnO nanostructure. The antimicrobial activity of synthesized nanostructures has been evaluated against the gram-positive human pathogenic bacteria, Staphylococcus aureus via an agarose gel diffusion test. The maximum value of zone of inhibition (22 mm) is achieved for 3 wt% Ag-doped ZnO nanostructure and it clearly demonstrates the remarkable antibacterial activity.

We report the fabrication of hierarchical-ordered superstructure Ag2CrO4 with platelet-like morphology via a facile hydrothermal method. Oriented attachment (OA) controlled growth arid hierarchical self-assembly of micrometer-sized platelets producing millimeter platelets are designed by autogenous pressure. A growth model is proposed: Ostwald ripening (OR) mechanism is predominant at low autogenous pressure (up to 400 bars), followed by a mixed (OA + OR) growth mode (at 600 bars) and the OA mechanism acts heavily in the high autogenous pressure domain (800 bars). The autogenous pressure is proved to be the key to thermodynamically hinder the OR growth in the initial stage. The difference between the surface energy of each crystal plane leads to the coalescence of the primary octahedral nanocrystals, and the one-dimension growth produces micrometer-size platelet-like crystals. Their self-assembly by sharing [100] crystallographic orientation allows the formation of hierarchical-ordered superstructures. Thanks to their limited particles size in nanoscale domains controlled by preferential growth mechanism, Ag2CrO4 hierarchical-ordered superstructures present an excellent photocatalytic activity for methyl blue under visible-light irradiation.

We present an unified approach of epitaxial strain and chemical substitution to induce ferromagnetic order in otherwise non-magnetic CaRuO3. The tensile and compressive strained CaRu1−xCrxO3 (0 < x ≤ 0.2) (CRCO) films deposited on SrTiO3 (100) and LaAlO3 (100) substrates, respectively, exhibit a magnetic moment larger than their bulk compositions. The compressive strained x = 0.15 film displays unusually large magnetic moment ∼1.4 μB/f.u. which is about one order of magnitude larger than that of its bulk counterpart. We show that this giant magnetic moment manifests in the realization of (i) a giant exchange bias of ∼700 Oe in CaRu0.85Cr0.15O3/Pr0.5Ca0.5MnO3 bilayer and (ii) a large hysteretic magnetoresistance; both potential attributes for the spintronic applications.

The non-magnetic and non-Fermi-liquid CaRuO3 is the iso-structural analog of the ferromagnetic (FM) and Fermi-liquid SrRuO3. We show that an FM order in the orthorhombic CaRuO3 can be established by the means of tensile epitaxial strain. The structural and magnetic property correlations in the CaRuO3 films formed on SrTiO3 (100) substrate establish a scaling relation between the FM moment and the tensile strain. The strain dependent crossover from non-magnetic to FM CaRuO3 was observed to be associated with switching of non-Fermi liquid to Fermi-liquid behavior. The intrinsic nature of this strain-induced FM order manifests in the Hall resistivity too; the anomalous Hall component realizes in FM tensile-strained CaRuO3 films on SrTiO3 (100) whereas the non-magnetic compressive-strained films on LaAlO3 (100) exhibit only the ordinary Hall effect. These observations of an elusive FM order are consistent with the theoretical predictions of scaling of the tensile epitaxial strain and the magnetic order in tensile CaRuO3. We further establish that the tensile strain is more efficient than the chemical route to induce FM order in CaRuO3.

The change from antiferromagnetism induced ferroelectricity to spin glass ferroelectric relaxor has been studied along the CuCr1−xVxO2 (0≤x≤0.5) solid solution of polycrystalline samples. As x increases from CuCrO2 (x=0) to CuCr0.82V0.18O2, it is found that the Néel temperature decreases from ∼24K down to ∼13K. This progressive weakening of the antiferromagnetism of CuCrO2 induces a rapid decrease of the spin induced ferroelectricity with polarization values going from ∼44μC/m2 down to ∼1.5μC/m2 for x=0.04 and x=0.08, respectively. Beyond x=0.18 (0.20≤x≤0.50), ac-magnetic susceptibility and magnetization measurements evidence a spin glass state while dielectric permittivity and polarization measurements point towards a relaxor behaviour. This shows that competing magnetic interactions in delafossites are an efficient way to transform a spin induced magnetoelectric into a multiglass (spin and dipolar) state.

It was previously reported that the synthesis of silver based delafossites as pure phases is challenging and requires more often delicate preparations as ion-exchange rather than simple solid state reaction or hydrothermal synthesis. For the first time, polycrystalline AgCrO2 samples are synthesized by a one-step reaction between Ag2O and Cr(OH)(3) in supercritical water conditions (400 degrees C, 40 MPa) using K2Cr2O7 as an oxidizing agent via a hydrothermal method. K2Cr2O7 is proved to be a good oxidizing agent, which avoids the formation of metallic silver and increases the solubility of precursors that lead to the formation of AgCrO2. The quality of the so-obtained compound is checked by structural as well as magnetic and optical properties characterizations.

A new approach, based on microwave heating, is used to synthesis CuCrO2 delafossite by solid state reaction, starting from Cu2O and Cr2O3. It is evidenced that microwave heating enhances solid state reaction kinetics as only 5min is needed to obtain pure samples. The quality of the products is attested by structural and physical properties characterizations. Powder X-ray diffraction and magnetic and electrical measurements show characteristics typical of the 3R delafossite. Scanning electron microscopy observation of the microstructure evidences a smaller size of the grains, compared to samples prepared by conventional solid state reaction method, which is confirmed by the particle size analysis.

The complex dielectric susceptibility and spin glass properties of polycrystalline CuCr0.5V 0.5O2 delafossite have been investigated. Electron diffraction, high resolution electron microscopy and electron energy loss spectroscopy show that the Cr3+ and V 3+ magnetic cations are randomly distributed on the triangular network of CdI2-type layers. In contrast to CuCrO2, CuCr0.5V 0.5O2 exhibits two distinctive (magnetic and electric) glassy states evidenced by memory effects in electric and magnetic susceptibilities. A large magnetodielectric coupling is observed at low temperature.