Organic molecule stabilized bismuth iodide nanoparticles: a hybrid system with multifunctional physical properties.

An organic-inorganic hybrid system of aniline stabilized bismuth iodide nanoparticles (ABI) was synthesized and investigated for its dielectric properties, AC-conductivity, polarization hysteresis and non-volatile memory performances. The X-ray diffraction result indicates the single phase crystalline nature of the nanoparticles and a microscopic image shows the homogeneous distribution of the bismuth iodide nanoparticles within the organic matrix. The material has exhibited a moderate dielectric performance via an interfacial polarization mechanism. The decrease in dielectric constant with frequency is correlated with the carrier concentration and diffusion potential, and the behaviour revealed that the halide ion mediated polaron migration controls the overall relaxation and conductivity properties of the material. Octahedral distortion of bismuth iodide, through halide ion migration, induced a hysteresis loop in polarization-electric field (P-E) characteristics. The device fabricated with the aniline stabilized bismuth iodide nanoparticles exhibited a space-charge limited current and trap assisted tunneling mechanism for the charge transport process. The non-volatile property reveals that the device has the ability to store binary information and has potential for memory applications.

The electrical behaviour of ultrafine bismuth phosphate particles under a range of temperature and frequency conditions.

Organic-molecule-stabilized ultrafine bismuth phosphate was synthesized by applying a wet chemical complexation-mediated route. Structural analysis confirmed the formation of monoclinic-phase nanoparticles made up of four-coordinated PO4 tetrahedral and eight-coordinated BiO8 polyhedral units. The dielectric, electrical conductivity, and impedance behaviour of the synthesized material was investigated under a wide range of frequency and temperature conditions. An alternating current conductivity study confirmed that the conduction process was followed by small and large polaron tunnelling mechanisms. An electric field-induced polarization study showed the formation of a hysteresis loop, generated as a result of the strong dipolar interactions through the Biδ+-Oδ--type covalent bonds.

Organic molecule functionalized lead sulfide hybrid system for energy storage and field dependent polarization performances.

A wet chemical route is reported for synthesising organic molecule stabilized lead sulfide nanoparticles. The dielectric capacitance, energy storage performances and field-driven polarization of the organic-inorganic hybrid system are investigated in the form of a device under varying temperature and frequency conditions. The structural analysis confirmed the formation of the monoclinic phase of lead sulfide within the organic network. The band structure of lead sulfide was obtained by density functional theory calculation that supported the semiconductor nature of the material with a direct band gap of 2.27 eV. The dielectric performance of the lead sulfide originated due to the dipolar and the space charge polarization. The energy storage ability of the material was investigated under DC-bias conditions, and the device exhibited the power density values 30 W/g and 340 W/g at 100 Hz and 10 kHz, respectively. The electric field-induced polarization study exhibited a fatigue-free behaviour of the device for 103 cycles with a stable dielectric strength. The study revealed that the lead sulfide-based system has potential in energy storage applications.

Electrical response of organic molecule supported preformed and in situ formed antimony sulfide nanoparticles under frequency conditions.

A complexation route mediated synthesis of orthorhombic antimony sulfide nanoparticles is described in this report where uniformly distributed particles within the size range of 2-12 nm are stabilized within the aniline matrix. The organic-inorganic hybrid system was investigated for dielectric capacitance and electric field-induced polarization performances under varying temperature and frequency conditions. The AC-conductivity revealed a correlated barrier hopping conduction mechanism in the hybrid system. A fatigue free polarization was achieved under the electric field of 9 kV mm-1 for the preformed antimony sulfide system with a stable value of 0.18 µC cm-2. The in situ dielectric capacitance and field dependent polarization measurements were also performed for the in situ synthesized antimony sulfide using the antimony-aniline complex as the precursor.

Resistive switching characteristics of carbon nitride supported manganese oxysulfide: an evidence for the sweep dependent transformation of polarity.

As part of a program to investigate the materials for resistive random access memory (ReRam) applications, a study has been conducted using embedded manganese oxysulfide (MOS) nanoparticles on the thin film of carbon nitride (CN). A high-temperature in-situ route was employed to synthesis CN-MOS composite where thiourea and manganese chloride was used as the precursor. The electrical property of the CN-MOS composite system (active layer), sandwiched between two gold electrodes, was measured under different sweeping (voltage) conditions. The device displayed different types of switching patterns, unipolar, and bipolar, by changing the sweep direction. The CN-MOS based device also exhibited good endurance and memory retention performances for the period of 104 cycles and 104 s, respectively, for both the polarities.

Enhancement of dielectric and electric-field-induced polarization of bismuth fluoride nanoparticles within the layered structure of carbon nitride.

A single-pot, wet chemical method has been reported for the synthesis of bismuth fluoride nanoparticles (BF) and functionalized BF within the network of carbon nitride (BFCN). In BFCN, a structural transformation of BF, from cubic to pseudo-cubic (as evidenced by Rietveld refinement analysis), confirmed the contribution of carbon nitride (CN) on functionalization. The effect of functionalization of BF has been investigated through dielectric and field-induced polarization studies under different temperature and frequency conditions. Enhancement of dielectric constant values was noticed in BFCN as compared with BF system, in the order of 2.5 (30 °C) and 8.0 (100 °C) at 100 Hz. Fatigue-free maximum polarization values of 0.041 µC/cm2 and 0.054 µC/cm2, under the electric field of 5 kV/mm, were achieved for BF and BFCN samples, respectively, for 5 × 103 cycles.

Organic-Inorganic Complexation Chemistry-Mediated Synthesis of Bismuth-Manganese Bimetallic Oxide for Energy Storage Application.

An organic-inorganic complexation method was applied for the synthesis of bismuth-manganese bimetallic oxide (BMO) nanoparticles where highly dispersed oxide particles were stabilized in an organic matrix (hexamethylenediamine). The as-synthesized hybrid material was subjected to microscopic, optical, and structural studies to gain comprehensive insights into the system. In the X-ray diffraction pattern, the majority of the diffracted peaks are matched to the orthorhombic phase of the Bi3Mn2O7 structure. To extract the electrochemical property, the hybrid system was applied as an anode material and investigated for supercapacitive performance under alkaline conditions. The specific capacitance obtained was 612 F·g-1 at the current density of 1 A·g-1, and under the same current density, the energy density and power density achieved were 137.78 W·h·kg-1 and 0.90 kW·kg-1, respectively.

Ammonium phosphomolybdate: a material for dielectric crossover and resistive switching performance.

The yellow ammonium phosphomolybdate [(NH4)3PMo12O40] (YAPM) is a robust and elegant compound that has found innumerable field applications. Herein, we have shown that this inorganic polymer serves as a novel dielectric material and a compound for memory device fabrication. It displays changeable dielectric performance and ac conductivity under UV (∼365 nm) irradiation. Drastic lowering of the dielectric constant (ε') was observed with the increase in dielectric loss factor, which was ascertained due to electron accumulation under UV exposure producing green APM (GAPM). The contributions of the Maxwell-Wagner polarization and the dipolar relaxation are correlated with the charge transfer and dielectric contribution of the material. Interestingly, the pressure-induced reduction of Mo(vi) to Mo(v) is reported for the first time and is similar to UV-exposed mixed-valence GAPM, which was corroborated by EPR spectra. In the ac signal, the crossover from quantum mechanical tunneling to hopping conduction is an adequate explanation for YAPM under UV irradiation. The fabricated device Au‖YAPM‖Au on a flexible paper substrate shows a resistive memory behavior that is modeled as a Schottky-type emission (SE) and Poole-Frenkel (PF) carrier transport for the OFF and ON states, respectively. The device exhibited a constant ON-OFF current ratio of 2 × 102 for YAPM. The OFF state endurance of the device (with 3 V pulses having 1 s time-period) under UV showed a steady increment current strength with time. After 100 s of UV exposure, the Au‖YAPM‖Au device became Au‖GAPM‖Au, and the conductivity completely shifted to a stable ON-state (at 300 s).

Copper-azide nanoparticle: a 'catalyst-cum-reagent' for the designing of 5-alkynyl 1,4-disubstituted triazoles.

A single pot, wet chemical route has been applied for the synthesis of polymer supported copper azide, CuN3, nanoparticles (CANP). The hybrid system was used as 'catalyst-cum-reagent' for the azide-alkyne cyclo-addition reaction to construct triazole molecules using substituted benzyl bromide and terminal alkyne. The electron donating group containing terminal alkyne produced 5-alkynyl 1,4-disubstituded triazole product whereas for alkyne molecule with terminal electron withdrawing group facilitate the formation of 1,4-disubstituted triazole molecule.

Graphene supported graphone/graphane bilayer nanostructure material for spintronics.

We report an investigation into the magnetic and electronic properties of partially hydrogenated vertically aligned few layers graphene (FLG) synthesized by microwave plasma enhanced chemical vapor deposition. The FLG samples are hydrogenated at different substrate temperatures to alter the degree of hydrogenation and their depth profile. The unique morphology of the structure gives rise to a unique geometry in which graphane/graphone is supported by graphene layers in the bulk, which is very different from other widely studied structures such as one-dimensional nanoribbons. Synchrotron based x-ray absorption fine structure spectroscopy measurements have been used to investigate the electronic structure and the underlying hydrogenation mechanism responsible for the magnetic properties. While ferromagnetic interactions seem to be predominant, the presence of antiferromagnetic interaction was also observed. Free spins available via the conversion of sp(2) to sp(3) hybridized structures, and the possibility of unpaired electrons from defects induced upon hydrogenation are thought to be likely mechanisms for the observed ferromagnetic orders.