M. Zubair Iqbal

Enhanced hydrogen storage performance for MgH2–NaAlH4 system—the effects of stoichiometry and Nb2O5 nanoparticles on cycling behaviour

Nowadays, the technological utilization of reactive hydride composites (RHC) as promising hydrogen storage materials is hampered by their reaction kinetics. In the present work, effects of reactant stoichiometry on ensuing hydrogen sorption properties and pathway of the MgH2–NaAlH4 (mole ratios 1:2, 1:1 and 2:1) system, both undoped and doped with Nb2O5 nanoparticles, were investigated. It was found that the as-prepared reactant stoichiometry of MgH2/NaAlH4 system had a profound impact on its dehydrogenation kinetics and reaction mechanism. Variable temperature dehydrogenation data revealed that undoped binary composites possessed enhanced hydrogen desorption properties compared to that of pristine NaAlH4 and MgH2. The use of Nb2O5 displayed superior catalytic effects in terms of enhancing dehydriding/rehydriding kinetics and reducing the dehydrogenation temperature of MgH2–NaAlH4 system. Isothermal volumetric measurements at 300 °C revealed that enhancements arising upon adding Nb2O5 were almost double that of undoped MgH2–NaAlH4 composites. The apparent activation energies for NaAlH4, Na3AlH6, MgH2, and NaH relevant decompositions in doped composite were found to be much lower than that for the undoped one. Moreover, Nb2O5 doping also markedly enhanced the reversible capacity of MgH2–NaAlH4 composites under moderate conditions, persisting well during three de/rehydrogenation cycles. XRD, XPS, and FESEM-EDS analyses demonstrated that reduction of Nb2O5 during first desorption was coupled to the migration of reduced niobium oxide species from the bulk to the surface of the material. It was suggested that these finely dispersed oxygen-deficient niobium species might contribute to kinetic improvement by serving as the active sites to facilitate hydrogen diffusion through the diffusion barriers both during dehydrogenation and rehydrogenation.

Silica-coated super-paramagnetic iron oxide nanoparticles (SPIONPs): a new type contrast agent of T1 magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI), a sophisticated promising three-dimensional tomographic noninvasive diagnostic technique, has an intrinsic advantage in safety compared with radiotracer and optical imaging modalities; however, MRI contrast agents are less sensitive than complexes used in other imaging techniques. Usually the clinically used Gd-based complexes MRI-T1 contrast agents are toxic; therefore, the demand for nontoxic novel T1-weighted MRI candidates with ultrasensitive imaging and advanced functionality is very high. In this research, silica-coated ultra-small monodispersed super-paramagnetic iron oxide nanoparticles were synthesized via a thermal decomposition method, which demonstrated themselves as a high performance T1-weighted MRI contrast agent for heart, liver, kidney and bladder based on in vivo imaging analyses. Transmission electron microscopy (TEM) results illustrated that the diameter of the SPIONPs was in the range of 4 nm and the average size of Fe3O4@SiO2 was about 30-40 nm. X-ray diffraction (XRD) and Raman spectroscopy analyses revealed the phase purity of the prepared SPIONPs. These magnetite nanoparticles exhibited a weak magnetic moment at room temperature because of the spin-canting effect, which promoted a high positive signal enhancement ability. MTT assays and histological analysis demonstrated good biocompatibility of the SPIONPs in vitro and in vivo. In addition, the silica-coated ultra-small (4 nm sized) magnetite nanoparticles exhibited a good r1 relaxivity of 1.2 mM-1 s-1 and a low r2/r1 ratio of 6.5 mM-1 s-1. In vivo T1-weighted MR imaging of heart, liver, kidney and bladder in mice after intravenous injection of nanoparticles further verified the high sensitivity and biocompatibility of the as-synthesized magnetite nanoparticles. These results reveal silica-coated SPIONPs as a promising candidate for a T1 contrast agent with extraordinary capability to enhance MR images.

Growth of monodisperse nanospheres of MnFe2O4 with enhanced magnetic and optical properties

Highly dispersive nanospheres of MnFe2O4 are prepared by template free hydrothermal method. The nanospheres have 47.3-nm average diameter, narrow size distribution, and good crystallinity with average crystallite size about 22 nm. The reaction temperature strongly affects the morphology, and high temperature is found to be responsible for growth of uniform nanospheres. Raman spectroscopy reveals high purity of prepared nanospheres. High saturation magnetization (78.3 emu/g), low coercivity (45 Oe, 1 Oe = 79.5775 Acm−1), low remanence (5.32 emu/g), and high anisotropy constant 2.84 × 104 J/m3 (10 times larger than bulk) are observed at room temperatures. The nearly superparamagnetic behavior is due to comparable size of nanospheres with superparamagnetic critical diameter Dcrspam. The high value of Keff may be due to coupling between the pinned moment in the amorphous shell and the magnetic moment in the core of the nanospheres. The nanospheres show prominent optical absorption in the visible region, and the indirect band gap is estimated to be 0.98 eV from the transmission spectrum. The prepared Mn ferrite has potential applications in biomedicine and photocatalysis.

Canted antiferromagnetic and optical properties of nanostructures of Mn2O3 prepared by hydrothermal synthesis

We have reported new magnetic and optical properties of Mn2O3 nanostructures. The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system. The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS), UV—visible spectroscopy, and the vibrating sample magnetometer (VSM). Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal. Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN = 83 K. Furthermore, the Mn2O3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration, resulting in hysteresis with large coercivity (1580 Oe) and remnant magnetization (1.52 emu/g). The UV—visible spectrophotometry was used to determine the transmittance behaviour of Mn2O3 nanostructures. A direct optical band gap of 1.2 eV was acquired by using the Davis—Mott model. The UV—visible spectrum indicates that the absorption is prominent in the visible region, and transparency is more than 80% in the UV region.

Controlled synthesis, phase formation, growth mechanism, and magnetic properties of 3-D CoNi alloy microstructures composed of nanorods

3-D flower like CoNi alloys nanostructures composed of nanorods have been synthesized by template free hydrothermal method at relatively low temperature (120 °C). The detailed characterizations confirm the formation of good crystalline fcc CoNi alloy, average crystallite size of 18.8 ± 1.0 nm, lattice parameter of 3.531 ± 0.01 A, and the nearly equiatomic composition (Co50Ni50). Highly uniform flower like nano structures are built up with nanorod of diameter about 100 nm and length in range of 200–400 nm. The nanorods (building blocks of flower) have single crystalline nature with [111] preferred growth direction. The concentration of NaOH plays a vital role in formation of alloys and high concentration promotes the formation of CoNi alloy at low temperature. The concentration of NaOH also affects the morphology remarkably by changing the growth/reaction rate of CoNi nanostructures and results in hollow spheres to nanoplate flower of CoNi alloys. Based on the evolution of the morphology of the products, a step wise growth mechanism is rationally proposed for flower like nanostructures by considering the effects of kinetic parameters on growth. Magnetic measurements show Co50Ni50 flower like nanostructure have high saturation magnetization, coercivity, remanent magnetization, and high effective anisotropy constant of value 101.3 emu g−1, 210.5 Oe, 16.2 emu g−1, and 4.457 × 104 J m−3 respectively. The enhancements of coercivity and effective anisotropy constant are attributed to nanoscale effects such as shape/surface anisotropy.

Phase Sensitive Behavior and Optical Properties of Cu0.45Mn0.55O2 Nanoparticles

In this work, we have reported a facile approach to fabricate the new Cu0.45Mn0.55O2 nanoparticles with novel properties. The detailed characteristic of the nanoparticles have been performed by X-Ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and UV-visible spectroscopy. HRTEM and SAED measurements point out that the nanoparticles are phase sensitive during exposure to electron beam irradiation and undergo a reversible transition from single crystal to polycrystalline. UV-visible spectrum indicates the direct band gap of 1.4eV as well as more than 80% transparency in UV region.

A facile fabrication route for binary transition metal oxide-based Janus nanoparticles for cancer theranostic applications

Janus nanoparticles (JNPs) have multiple configurations for molecular imaging, targeting, and therapeutic effects on cancers; these properties have made these particles attractive for biomedical applications. Nonetheless, smart strategies for the controlled synthesis in a liquid phase and exploration of the appropriate applications of JNPs remain a challenge. In this study, a unique liquid-phase method was applied to fabricate Mn3O4-TiO2/ZnO/Fe3O4 multifunctional binary transition metal oxide-based JNPs, using the concept of epitaxial growth and lattice mismatch among synthesized materials. Transmission electron microscopy and scanning transmission electron microscopy results revealed that the created materials are embedded in the form of dimers with good dispersion and homogeneous growth in a nonpolar solvent. Pluronic® F-127-coated Mn3O4- TiO2 JNPs were utilized as a contrast agent in T1-weighted magnetic resonance imaging (MRI) and in photodynamic therapy (PDT) for cancers in vitro and in vivo. In vivoT1-weighted MRI of the heart, liver, and kidneys in mice after intravenous injection of the nanoparticles revealed high sensitivity and biocompatibility of as-synthesized Mn3O4-TiO2 JNPs. Results of synchrotron X-ray fluorescence microscopy mapping showed the stability of the nanocomposites and efficiency of penetration into the cytoplasm and perinuclear area. Inorganic TiO2 photosensitizers showed promising tumor ablation performance in PDT in vitro and in vitro at low intensity of UV irradiation (5.6 mW.cm–2) because of their ultrasmall size and photodegradable stability. These results reveal that multifunctional Mn3O4-TiO2 JNPs enhance a T1-weighted MRI contrast and have excellent properties for PDT and therefore, may be a novel agent for cancer theranostics.

High-Performance Colorimetric Detection of Thiosulfate by Using Silver Nanoparticles for Smartphone-Based Analysis

Developing thiosulfate (S2O32-) sensors with silver nanoparticles (AgNPs) for analysis of aqueous solutions with the interference of other anions remains challenging. In this study, we propose a new strategy for excellent selective colorimetric detection of S2O32-. The nonmorphological transition of AgNPs leading to a color change from yellow to brown is verified by UV-vis, TEM, DLS, SEM, and XPS analyses. The sensor exhibits high sensitivity with detection limits of 1.0 μM by naked-eye determination and 0.2 μM by UV-vis spectroscopy analysis. The linear relationship (R2 = 0.998) between the (A0 - A)/A0 values and S2O32- concentrations from 0.2 μM to 2.0 μM indicates that the fabricated AgNPs-based colorimetric sensor can be employed for quantitative assay of S2O32-. Colorimetric responses are also monitored using the built-in camera of a smartphone. The sensor shows a linear response to S2O32- in 0-20.0 μM solutions under the optimized conditions and is thus more suitable for rapid on-site tests than other detection methods. A smartphone application (app) is downloaded under Android or IOS platforms to measure the RGB (red, green, blue) values of the colorimetric sensor after exposure to the analyte. Following data processing, the RGB values are converted into concentration values by using preloaded calibration curves. Confirmatory analysis indicates that the proposed S2O32- colorimetric sensor exhibits feasibility and sensitivity for S2O32- detection in real environmental samples.

Controllable synthesis of Fe3O4 nanoflowers: enhanced imaging guided cancer therapy and comparison of photothermal efficiency with black-TiO2

Photothermal therapy (PTT) has emerged as one of the promising cancer therapy approaches. However, nanoparticles (NPs) which are used for PTT might be biopersistent and potentially toxic. The current research explores the promising use of Fe3O4 nanoflowers as nontoxic, efficient photothermal, and strong T2 type magnetic resonance imaging (MRI) contrast agents for imaging-guided photothermal cancer therapy. In this study, a facile solvothermal method is used to fabricate PEG-coated Fe3O4 nanoflowers with controllable dimensions. Their successful fabrication, the effect of the reaction parameters, and their magnetic properties are investigated in depth. The therapeutic performance of the Fe3O4 nanoflowers (Fe-NFs) is evaluated and compared with commercially available black TiO2 nanoparticles (b-TiO2) under an 808 nm laser. The photothermal therapy efficiency of the Fe-NFs is observed to be better than that of the reported Fe3O4 nanoparticles. In vitro and in vivo investigation demonstrates that the therapeutic performance of the Fe-NFs is comparable to that of b-TiO2. Moreover, the Fe-NFs show excellent magnetic properties and magnetic resonance imaging capability to monitor therapeutic performance.

Synthesis, characterization and applications of maghemite beads functionalized with rabbit antibodies

Magnetic nanoparticles (NPs) have attracted great attention owing to their applications in the biomedical field. In the present work, maghemite (γFe2O3) NPs of 6.5 nm were prepared using a sonochemical method and used to prepare magnetic beads through silanization with 3-aminopropyltrimethoxysilane (APTS). Subsequently, amino groups in the resulting APTS-γFe2O3 beads were converted to carboxylic acid (CARB-γFe2O3) through the succinic anhydride reaction, as confirmed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and dynamic light scattering (DLS) measurements. The size of these beads was measured as 12 nm and their hydrodynamic diameter as 490 nm, using TEM analysis and DLS, respectively. The CARB-γFe2O3 beads were further functionalized by immobilizing rabbit antibodies on their surfaces; the immobilization was confirmed by flow cytometry and ionic strength. The samples were further characterized by Mössbauer spectroscopy and DC magnetization measurements. Studies on magnetic relaxivities showed that magnetic beads present great potential for application in MR imaging.