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Research and technology development of lithium ion battery is very important nowadays because of its high energy and power density, low self discharge, no/less memory effect, comparatively high current output. It has been largely used in various fields like hybrid electric vehicles (EV's), portable devices, digital cameras and many more. As per our knowledge this is the first report on the synthesis of KTaO3 and examination of electrochemical performance on lithium ion batteries (LIB). The flower like nanostructured KTaO3 exhibits high interfacial area and less path length for charge transfer, which was the main reason to exhibit good electrochemical properties. The average crystallite size of material was confirmed by XRD analysis and found to be ~26 nm. The high irreversible capacity was recorded at 1307 mAh g−1 with high Columbic efficiency (~99%) at potential window of 0.01–3.00 V. Moreover, reversible first discharge capacity was measured at 432 mAh g−1 at 0.1 C current rates with exemplary cyclic stability. The capacity fade was negligible for consecutive cycles. Even at very high current rate (3C) also it presents good capacity of 74 m Ahg−1 with excellent reversibility. In addition, electrochemical impedance spectra prove the less conductive resistance at higher frequency region. Finally the present work explains the excellent electrochemical performance of nanostructured flower like KTaO3 for Li-ion battery as anode material.

Two-dimensional (2D) conducting metal-organic frameworks (MOFs) is an emerging family of porous materials that have attracted a great attention due to their outstanding inherent properties such as hierarchical porosity, diverse architectures with high surface area and excellent electrical conductivity. These unique features make them ideal candidates for electrochemical energy storage technologies. This review highlights the key innovations on 2D conducting MOFs with emphasis on the design and synthesis strategies, and their potential applications in energy storage systems. Several recent breakthrough examples of 2D conducting MOFs with enhanced electrochemical performances are outlined. The review further extends the discussion on the significance of Nuclear Magnetic Resonance Spectroscopy (NMR) to understand the charge storage kinetics and their impact on structural implications of the materials. The elucidation of structure-property-performance relationship will further guide the development of new architectures of 2D conducting MOFs for the high-performance energy storage devices.

In the recent times, global interest on plant-based research has increased significantly. Through this article, a simple heat treatment method to synthesize Centella asiatica (CA) powder has been suggested. The synthesized samples have been subjected to various structural and morphological characterizations, in addition to electrochemical studies. Although the medicinal value of Centella asiatica is well known, its use in other applications is hardly explored. Hence, by combining the cyclic nature of CA and the layered structures of carbonaceous materials, composites of Centella asiatica with graphite powder, GO and rGO have been prepared for the first time and their photocatalytic and electrochemical properties have been investigated. In spite of some agglomeration and flake like structures, the nanosize (14 nm) of the prepared CA sample contributes largely to the aforementioned applications. One of the phenomenal aspects of the synthesized sample is that the low energy gap and high conductivity makes it an excellent photocatalytic material which is also evident from its ability to decolorize AO 8 dye under UV light to a great extent. Among the composites of CA-carbonaceous materials prepared, Centella asiatica-rGO exhibited superior electrochemical properties with high capacitance and low charge transfer resistance.

A rapid and facile method for the detection of hydrogen peroxide (H2O2) in chemical reactions has been reported using molybdenum oxide Nanoparticles (MoO3 NPs) synthesized via an eco-friendly and economical solution combustion route using Centella Asiatica leaf powder. The formation of porous agglomerated NPs has been confirmed by subjecting the synthesized material to various analytical and spectroscopic techniques to understand their size, morphology, and nature. In this study, MoO3 NPs-based electrode has been fabricated and its electrochemical sensing capabilities have been investigated. Electrochemical investigation of hydrogen peroxide exhibits an increase in the peak current response at pH 13. The cyclic voltammetry (CV) results indicate an appreciable reversibility of the electrode reaction. The anodic and cathodic peaks show a greater inclination towards the positive and negative sides with a significant development in the reversibility of the oxidation and reduction states. These findings open up new avenues for the exploration of various other metal oxide based NPs as sensors for the detection of chemically toxic substances.

A green combustion method using Aloe vera latex as a fuel was employed to synthesize nanocrystalline cupric oxide (CuO). The nanocrystalline nature and phase of CuO was confirmed by powder X-ray diffraction. Applying the Kubelka–Monk function to diffuse reflectance spectra showed the band gap of CuO to be 1.632 eV. Paracetamol and d -glucose in 1 M KOH solution were sensed using a carbon paste electrode modified using CuO nanoparticles (NPs). The cyclic voltammetry results suggest that CuO NPs possess superior electrochemical properties due to a lower value of the difference between oxidation and reduction potential (EO-ER). The proton diffusion coefficient for CuO electrode material was1.5047 × 10−5cm2s−1. Electrochemical impedance and Bode studies confirmed that the charge-transfer resistance value of CuO NPs was on the lower side due to the phase angle (55°) being near to ф = ᴨ/2. The electrochemical behavior indicates that CuO is a promising electrode material for sensing molecules such as paracetamol and glucose.

A new nanocomposite has been prepared embedding CuO nanoparticles as an additive into grafted β-nickel hydroxide electrode and their electrochemical performance in KOH electrolyte have been investigated. β-nickel hydroxide (β-Ni(OH)2) has been prepared by a simple precipitation method. Ni(OH)2/NiOOH, the main active materials in the pasted nickel electrode have been prepared using nickel mesh in the form of current collector. A study on the electrochemical performances of the pure β-Ni(OH)2 and CuO added β-Ni(OH)2 electrodes in 6.0 M KOH electrolyte has revealed that CuO embedded β-Ni(OH)2 displays much higher specific capacitance and better cyclability than pure β-Ni(OH)2. In fact, the addition of CuO improves the reversibility of the electrode by reducing the anodic (Epa) and cathodic (Epc) peak potential difference and also increases the separation of the oxygen evolution (EOE) and anodic (Epa) peak potential. Further, CuO nanoparticles grafted β-Ni(OH)2 electrode displays elevated proton diffusion co-efficient (D) and inferior charge transfer resistance. Specifically, CuO embedded β-Ni(OH)2 exhibits 855 F g−1 at 5 Ag-1 and good cycling stability as it maintains more than 90% of its original capacitance even after 3000 cycles. The enhancement may be attributed to the nanosize of CuO and chemical interaction between CuO and β-Ni(OH)2. These results are expected to offer new insight to future researchers who wish to work on the development of novel electrode materials for energy storage applications.

Removal of the hazardous and endocrine-disrupting 2,4-dichlorophenol (2,4-DCP) from water bodies is crucial to maintain the sanctity of the ecosystem. As a low bandgap material (1.37 eV), NaBiS2 was hydrothermally prepared and used as a potential photocatalyst to degrade 2,4-DCP under visible light irradiation. NaBiS2 appeared to be highly stable and remained structurally undeterred despite thermal variations. With a surface area of 6.69 m2/g, NaBiS2 has enough surface-active sites to adsorb the reactive molecules and exhibit a significant photocatalytic activity. In alkaline pH, the adsorption of 2,4-DCP on NaBiS2 appeared to decrease whereas, the acidic and neutral environments favoured the degradation. An increase in the photocatalyst dosage enhanced the degradation efficiency from 81 to 86 %, because of higher vacant adsorbent sites and the electrostatic attraction between NaBiS2 and 2,4-DCP. The dominant scavengers degraded 2,4-DCP by forming a coordination bond between chlorine's lone pair of electrons and the vacant orbitals of bismuth, following the order hole> OH > singlet oxygen. Being non-toxic to both natural and aquatic systems, NaBiS2 exhibits antifungal properties at higher concentrations. Finally, the electron-rich NaBiS2 is an excellent electrocatalyst that effectively degrades organic pollutants and is a promising material for industrial and environmental applications.

Fig. 1 and the Graphical Abstract were created by Heno Hwang, scientific illustrator at King Abdullah University of Science and Technology (KAUST). The research reported in this publication was supported by funding from KAUST. The funding support from Department of Science and Technology’s Technology Mission Division (No. OST/TM O(EWO)/OWUIS20IS/TS-03 (G)) under the program “Optimal Water Use in Industrial Sector” is greatly acknowledged.

The dysfunctioning of β-cells caused by the unspecific misfolding of the human islet amyloid polypeptide (hIAPP) at the membrane results in type 2 diabetes mellitus. Here, we report for the first time, the early-stage interaction of hIAPP oligomers on the DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) lipid membrane using electrochemical parameters. Electrochemical techniques are better than other techniques to detect hIAPP at significantly lower concentrations. The surface level interactions between the peptide (hIAPP) and lipid membrane (DMPC) were investigated using atomic force microscopy (AFM), confocal microscopy (CM) and electrochemical techniques such as Tafel polarization, cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Inserting IAPP into the fluid domains results in breaking the lipid-to-lipid interaction, leading to restriction of membrane mobility. The SLateral values of the liposome and IAPP co-solubilized liposome indicates the cooperative insertion of IAPP. Further, a new method of immobilizing a membrane to the gold surface has been employed, resulting in an electrical contact with the buffer, preventing the direct utilization of a steady-state voltage across the bilayer. The electrochemical studies revealed that the charge transfer resistance decreased for 3-mercaptopropanoic acid modified gold (MPA-Au) electrode coated with the liposome and after the addition of IAPP, followed by an increase in the capacitance. The present study has opened up new dimensions to the understanding of peptide-membrane interactions and shows different experimental approaches for the future researchers in this domain.

The persistence of hollow centre in the carbon obtained from milkweed floss provides exceptional sorption characteristics, not seen in common biomasses or their derivatives. A considerably high sorption of 320mg of lead per gram of milkweed carbon was achieved without any chemical modification to the biomass. In this research, we have carbonized milkweed floss and used the carbon as a sorbent for lead in waste water. A high surface area of 170m2g-1 and pore volume of 1.07cm3g-1 was seen in the carbon. Almost complete removal (>99% efficiency) of lead could be achieved within 5min when the concentration of lead in the solution was 100ppm, close to that prevailing in industrial waste water. SEM images showed that the carbon was hollow and confocal images confirmed that the sorbate could penetrate inside the hollow tube.

The importance of Ni-based batteries in the present context is extremely valuable, as their electrochemical properties are expected to offer significant insights into their application as battery materials. In this direction, Ni(OH) 2 has been prepared using the co-precipitation method by varying the concentrations of zinc additive (2, 4, 6 & 8 wt%) and pH (8, 9, 10 & 11). The results show that the prepared samples exist in β-phase with flake like structure. The electrochemical properties of b-Ni(OH) 2 have been investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements using a paste-type electrode on a nickel mesh as a current collector. The cyclic voltammetry measurements indicate that the reversibility of the electrode reaction increases at pH 10 and 6% Zn additive. Whereas, the EIS measurements reveal that a reduction in the charge transfer resistance increases the double layer capacitance of the nickel electrode.

In this paper, the performance of Fe based redox flow batteries (IRFBs) was dramatically improved by coating N-doped carbon spheres (NDCS) on the graphite felt electrodes. NDCS was synthesized by the single-step hydrothermal method using dextrose and ammonia as a precursor and coated over a graphite felt electrode by electrostatic spraying. The weight of NDCS required for the modification of the electrode to achieve the effective performance of the battery was studied using electrochemical techniques. Cyclic voltammetry (CV) and potentiodynamic polarization study was used to evaluate the kinetic reversibility and linear polarization resistance offered by the electrode towards electrolyte. The characterizing features of the NDCS, untreated graphite felt (UGF) electrode, and optimized modified graphite felt (MGF) electrode were analyzed using SEM, EDAX, XRD, and Raman spectroscopy. The charge-discharge studies were performed for the 132 cm2 IRFB using a 2 mg/cm2 MGF electrode as a positive electrode by varying the current densities from 20 to 60 mA/cm2. The cell resulted in an average coulombic efficiency (CE) of 93%, voltaic efficiency (VE) of 72%, and energy efficiency (EE) of 68% for 15 cycles at the current density of 30 mA/cm2. The improvement in the performance of the IRFB is due to the presence of electrochemically active nitrogen-bearing carbon catalysts. In this paper, the pioneering effort has been made to improve the efficiency of the IRFB with an active area of 132 cm2 using glycine as the ligand.

Dye-sensitized solar cells (DSSCs) are an efficient and versatile method of transforming the clean and most plentiful energy resources available. DSSC is translucent to some extent and relatively inexpensive than the traditional solar cell. Thus, it may be a possible source of electricity for the future. But other things need to be focused on before it is considered a viable commercial product. The review discusses these facets and the numerous changes the DSSC has experienced in the recent years. Photoelectric conversion systems struggle to fulfil the specifications of constant power output owing to the erratic and unstable characteristics of the solar radiation. With the evolution of rechargeable electric energy storage systems (ESSs), the integration of a DSSC and ESSs has developed into a promising approach to solve this issue. Here, we describe the working principle, recent progress of DSSCs, including photoanodes, sensitizers, electrolytes, and counter electrodes, and the use of DSSCs in energy storage, targeting DSSC and supercapacitor (SC) integrated devices. The future prospects for highly effective, reliable DSSC and DSSC-SC development have also been highlighted.

Synthesis based on biomaterial technology has high potential in structural applications. Blending metal oxides with plant extract is an attractive alternative for preparing materials with superior material properties. Here, we report for the first time, the synthesis of NiO bio-composite materials by employing Aloe vera leaf extract. The work mainly highlights the synergistic influence of biomolecules of Aloe vera plant on the electrochemical and photocatalytic properties of NiO. The structure, morphology, band gap and bonding features of NiO bio-composites were characterized by XRD, Electron Microscopy, UV-DRS and FT-IR techniques, respectively. The average crystallite size of the composites was within 60 nm. FT-IR spectra confirmed the strong bonding interactions between biomolecules and NiO. A maximum band gap of 3.88 eV with a good thermal stability for the synthesized composites was observed. The addition of biomolecules to NiO resulted in the improvement of the reversibility of the electrode by reducing the anodic (Epa) and cathodic (Epc) peak potential difference in KOH electrolyte. Also, the composite exhibited greater stability due to recyclability and less resistance even after 1000 charge-discharge cycles, revealing a stable electrode material for supercapacitors applications. The photocatalytic experiments confirmed a maximum of 95% dye degradation efficiency by the composite for AR88 dye. It was also found that 50 % of dye degradation occurred within 74.61 min. The encouraging results project out the potential of the synthesized NiO-biocomposites to be a better supercapacitor and photocatalyst.

By employing a simple hydrothermal process, a new class of ternary alkali metal-based chalcogenide (NaFeS2 (NFS)) has been produced and anchored on to reduced graphene oxide (rGO) sheets for the first time. Transition metal-based chalcogenides (TMC) exhibit limited conductivity because of their semiconducting nature and hence, engineering TMCs with 2D carbonaceous materials yields better catalytic performance. Alkali metal-based chalcogenides and their composites appear to be promising alternatives, whose electrochemical properties haven't been explored much. This work presents a detailed insight into the structure and morphology of the prepared NFS-rGO composite, along with its electrochemical properties. The cyclic voltammetry (CV) response at the NFS-rGO composite electrode for the redox probe K4Fe(CN)6 is better with low peak to peak separation potentials (ΔEp ​= ​99 ​mV) compared to the individual components NFS (ΔEp ​= ​190 ​mV) and GO ( ∆ E p ​= ​130 ​mV), indicating a better electron transfer kinetics. The NFS-rGO composite electrode displays an enhanced electrocatalytic activity as evidenced by the high electrochemically active surface area (6.09 ​× ​10−2 ​cm2) and the heterogeneous electron transfer rate constant (k0 ​= ​5.4 ​× ​10−2 ​cms−1). In general, the NFS-rGO composite exhibits excellent material as well electrocatalytic properties due to the synergistic effect between NFS and rGO and can further be explored for electrochemical sensing applications as well.

A custom designed DNA probe against cry1 gene of Bacillus thuringiensis has been used to fabricate a DNA biosensor by self-assembled monolayers of mercaptohexanol (MCH) and thiol-linked custom designed probe (ssDNA-thiol), immobilized on a screen printed gold nanostructured electrode. DNA immobilization and hybridization have been characterized by differential pulse voltammetry (DPV) using methylene blue as an electrochemical hybridization indicator. With this approach, the target DNA could be quantified in the range of 1.0 × 10−6 M to 1.0 × 10−12 M, with a detection limit of 0.997 × 10−12 M by 3σ. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) have been performed to characterize the sequentially modified electrode. In addition, a non-complementary DNA sequence of Bacillus cereus has been tested as a non-target, that hardly causes any variation in the reduction current of MB reaffirming that the DNA-based biosensor is high selective to Bacillus thuringiensis. The electrochemical detection methods employed in this work can be extended further to develop DNA-based biosensors for the detection of other microorganisms having applications in agriculture, food industries and medical applications.

For large-scale energy storage, iron-based flow batteries (IRFBs) have been considered as a better choice because of their low-cost and use of environmentally friendly iron-based salts. The development of a IRFBs has been limited by the sluggish kinetics of the reaction, especially at the positive electrode during charging. Therefore, it is very important to look for stable electrolytes and superior electrode materials along with their modifications. Carbon-based electrodes are majorly used in IRFBs and these electrodes are feasible to modify using electrocatalysts. In the current study, nitrogen-doped carbon particles (NICaps) derived from Bermuda grass were used to modify graphite felt electrode. SEM, EDAX, Raman, and XPS analysis were used to characterize the modified graphite felt (MGF) electrode. It was observed that the NICaps MGF electrode had a significant improvement in electrochemical properties. The cathodic and anodic peak currents for the MGF electrode (1.55 and 1.63 mA/cm2 respectively) had a remarkable increase in comparison with the untreated graphite felt electrode (UGF) (0.48 and 0.88 mA/cm2 respectively). The Nyquist plot and the data derived from the equivalent circuit indicated lower charge transfer resistance for MGF. The charge-discharge studies carried out using 132 cm2 cell reveals that the modified electrodes result in higher current uptake of 50 mA/cm2 whereas the current uptake from the UGF electrode was limited to 20 mA/cm2. The battery resulted in an average coulombic efficiency of 95%, the peak power density of 60 mW/cm2, and better stability during multiple cycling.

Polyethylene tetraphthalate (PET) bottles, a major environmental pollutant from the food industry, has been used as an activated carbon source in the current work. The specific surface area of the activated carbon has been analyzed using N2 adsorption/desorption isotherms, at different sonication time periods. A high surface area of 899 m2 g-1 with microporosity has been achieved for 20 h sonication followed by activation at 800 °C. To further enhance the material performance, carbon doped MoS2 (MoS2–C), using conventional hydrothermal technique has been synthesized. Different composite ratios of activated carbon and MoS2-C have been tested using electrochemical impedance spectroscopy and the best ratio owing to lesser charge-transfer resistance has been chosen for supercapacitor and HER analysis. The porous network of the plastic derived activated carbon (PAC) with a few layers of MoS2–C contributes significantly to the increase in the power density (469 W kg-1). By inducing defects on the material surface, there has been a significant enhancement in the electrocatalytic activity on PAC and this facilitates HER on its surface. Subsequently, the HER activity of the PDAC/MoS2–C composite has also been reported. Here, the PDAC defective sites along with the hexagonal MoS2–C’s largely exposed reactive edges indicate a reduction in the overpotential and Tafel values of −195 mV and −82 mVdec−1, suggesting that the material under investigation is a good catalyst for electrochemical HER. Also, this article reports for the first-time, HER activity of defect induced plastic derived activated carbon and its excellent catalytic activity.

A new photocatalytic material sodium iron disulfide (NaFeS2) has been synthesized via a hydrothermal method for the degradation of methylene blue (MB) and indigo carmine (IC). This material has been subjected to various analytical, electrochemical and photocatalytic studies to understand its morphology, crystallinity, band gap, oxidation-reduction potential and ability to catalyse the rate of dye degradation. The material exists as nanorods with a thickness of 30–100 nm and a monoclinic phase with an average crystallite size of 25–30 nm. The energy bandgap of the prepared photocatalyst has been calculated using the Kubelka-Munk function and is found to be 2.01 eV. Using a UV light source, the photocatalytic activity of NaFeS2 has been carried out, where the time of irradiation determined the ability of the catalyst to degrade the dye under investigation. With a degradation efficiency of 97% in 105 min for MB and 99% in 45 min for IC, NaFeS2 appears as an excellent photocatalytic material. The electrochemical studies also act as a testament for NaFeS2’sadmirable photocatalytic property. The photocatalytic and electrochemical activities of NaFeS2 offer an innovative platform for the treatment of various other environmental pollutants as well.

In the recent times, cost-effective and eco-friendly processes of synthesizing nanoparticles (NPs) have emerged as a substitute to conventional synthetic methods. Several research groups in the past have synthesized silver oxide (Ag2O) nanoparticles from various plant extracts and have been extensively reported. A first of its kind facile green combustion method has been adopted here to synthesize Ag2O NPs using Centella asiatica and Tridax plant powder. The unique pentacyclic and triterpene constituents of Centella asiatica and Tridax powder has kindled our curiosity to explore their electrochemical, photocatalytic and biological activities that may contribute to various environmentally benign industrial applications. The cyclic voltammetric studies show that the cathodic and anodic peak potentials for the synthesized Ag2O NPs exhibit hysteresis in the range of 0.3 V to –0.1 V. A high percentage of degradation of acid orange 8 (AO8) dye by the synthesized Ag2O NPs offers new hope on its potential photocatalytic activity. Finally, their anti-bacterial and anti-fungal activities carried out against S. epidermidis and S. aureus and A. fumigates and A. aureus respectively, have shed new light on the ability of the synthesized Ag2O NPs to inhibit the growth of various disease-causing pathogens. Hence, it is believed that this research work will act as a fundamental basis to various researchers and industrialists working in the energy, water and biological fields to carry out advanced studies in the aforementioned domains.

The molar volume and compressibility of (glycylglycine + CuCl2) in aqueous ethanol mixtures have been obtained at four different temperatures T = (288.15 to 318.15) K from ultrasonic velocity and density measurements. Excess molar volumes were found to be negative throughout the composition range indicating notable changes in hydrogen bonding and electrostatic interactions. Using the Prigogine–Flory–Patterson theory, quantitative estimation of different contributions, i.e. interactional, free volume, and P∗ effect to VE have been obtained. The molar isentropic compressibility has been computed using the ultrasonic velocity and excess volume data. The trends in κ S E are affected by the size of the molecule leading to negative contributions. In order to compare the theoretical values of ultrasonic velocity, the equations of Nomoto and Junjie were used and found to predict the experimental data very well.

Chitosan–Co3O4 composite films have been prepared by solution casting method. The obtained films have been characterised by XRD and FESEM. The electrical properties of the films are examined by impedance spectroscopy in the temperature range 303–343 K. The impedance plot of the films pronounces the role of temperature in charge-transfer resistance of the composite. Frequency as well as temperature dependencies of dielectric constant and dielectric loss exhibit the general trend followed by carrier dominated dielectrics. Electric modulus parameters give an insight on the ionic conductivity and relaxation phenomena of the composite films. The dielectric parameters along with modulus data have been exploited to discuss the conduction mechanism in the material. The minimum activation energy of 3.9 kJ mol−1 and maximum room temperature conductivity of 1.94 × 10−2 S cm−1 were found for composite film with 8% Co3O4 content.

The excess molar volumes ( V E ), viscosity deviations (Δ η ), deviations in isentropic compressibility (Δ κ S ) and excess molar refractivity (Δ R m E ) for {(glycylglycine + ZnCl 2 ) in aqueous methanol} mixture have been calculated from the experimental values. The bridging water molecules bend the chains into stable open ring structures together with intermolecular hydrogen bonding and interstitial accommodation leading to negative V E values. The positive Δ η values indicate a structure breaking effect of aqueous glycylglycine–ZnCl 2 upon contact with methanol molecules. It is also noted that chelation of zinc to glycylglycinate is through carboxylic group and not the amino group. The negative Δ κ S values suggest the formation of an open ring structure lowering the entropy of the solution. Due to weak interaction between solute and solvent, the molecular structure of individual molecule does not change significantly and leads to negative Δ R m E values. Finally, the results have lead to a good understanding of the thermodynamics properties of the studied liquid mixture.

An efficient microwave-assisted route has been used to synthesize nanoparticles of cobalt oxide. The particles were well characterized by transmission electron microscopy (TEM) which showed that the average diameter of the particles is around 6 nm. X-ray diffraction (XRD) studies further confirmed the formation of the spinel Co3O4. Purity of the products was detected by Fourier transform infrared spectroscopy (FTIR) combined with thermal gravimetric analysis (TG/DTG). The magnetic measurements revealed a small hysteresis loop at room temperature indicating a weak ferromagnetic nature of the synthesized Co3O4 nanoparticles. The magnetic moment of the particles was measured to be 4.27 μeff.

Volumetric and acoustical parameters are reported for glycylglycine in aqueous NiCl2 solution at T = (288.15–318.15) K. The apparent molar volumes and isentropic compressibilities were calculated from the experimental data of ultrasonic velocity and density. Together with these, excess isentropic compressibility ( κ S E ), excess free volume ( V f E ), excess intermolecular free length ( L f E ) and deviations of ultrasonic velocity (Δu) were obtained. The results are interpreted in terms of molecular interactions. The results show that the cation and anion play a significant role in influencing the behavior of glycylglycine in aqueous solutions. These effects were also attributed to the doubly charged behavior of glycylglycine and to the formation of physically bonded ion-pairs between charged groups of glycylglycine and cation and anion of the electrolyte.

The densities, viscosities and ultrasonic velocities for glycylglycine–NiCl 2 in aqueous ethanol mixtures have been studied in the temperature range 288.15–318.15 K. The excess molar volumes, viscosity deviations and changes in isentropic compressibility for the binary mixtures have been calculated and discussed in terms of hydrogen bonding and structure-breaking effect. The computed results are fitted to the Redlich–Kister polynomial. The results clearly indicate that there is a strong association in the mixtures studied.

Ultrasonic velocity ( u ), density ( ρ ), and viscosity ( η ) have been measured for glycylglycine and CoCl 2 in aqueous and aqueous ethanol systems at T = (288.15 to 318.15) K. Using the experimental values, the adiabatic compressibility ( κ s ), molar hydration number ( n H ), apparent molar compressibility ( K S Φ ), apparent molar volume ( V Φ ), limiting apparent molar compressibility ( K S ϕ 0 ), limiting apparent molar volume ( V ϕ 0 ), their constants ( S K , S V ), viscosity coefficients of A and B parameters of Jones–Dole equation, relative viscosity ( η r ), and excess Gibbs free energy of activation ( ΔG ∗E Δ G ∗ E ) were calculated and the results of all these parameters have been discussed in terms of solute–solvent and solute–solute interactions.

Volumetric, acoustic, refractometric, excess and deviation properties of glycylglycine–MnCl2 in aqueous ethanol mixtures have been reported at T = (288.15 to 318.15) K. Redlich–Kister equation was used to fit the derivate properties. The experimental data of the constituent binaries were analyzed to discuss the nature and strengths of intermolecular interactions. The interdependence of Lf and u has been evolved from Eyring and Kincaid model. The variations in specific acoustic impedance revealed that hydrogen bonding was predominant in the studied binary mixtures. Solvation number indicated structure-breaking tendency of the solute and weakening of local solvent structure.