Alfa Sharma

Shape-controlled CoFe2O4 nanoparticles as an excellent material for humidity sensing

The humidity sensing performance of cobalt ferrite nanoparticles (CoFe2O4 NPs) with controlled morphology obtained via a solution route is reported in this work. The humidity sensing properties of the presented CoFe2O4 NPs ferrite sensor were investigated by exposing it to a broad humidity range of 8–97% at room temperature. CoFe2O4 NPs with spherical, cubic, and hexagonal shapes have been successfully achieved by tuning the growth conditions like reaction time and amount of solvent. These CoFe2O4 NPs exhibit morphology-dependent chemi-resistive humidity sensing behaviors. The highest humidity sensitivity value of ∼590 along with response/recovery value of 25/2.6 s at room temperature was obtained for CoFe2O4 hexagonal (CF-H) shape as compared to CoFe2O4 spherical (CF-S) and CoFe2O4 cubic (CF-C) shapes. Freundlich adsorption isotherm model was well fitted with the experimental results which turned up in support of a plausible humidity sensing mechanism. The morphology-dependent CoFe2O4 nanostructures exhibit promising sensing capabilities which ensure them as a potential candidate for magnetic recording media and next-generation humidity sensors.

Field electron emission from hydrogenated amorphous silicon films on tungsten: Light‐induced effects

Field electron emission from a hydrogenated amorphous silicon deposited tungsten tip has been studied. The effect of prolonged (hourly) exposure to light on the field electron emission current has been investigated. The current‐voltage characteristics of the as‐deposited, light exposed, and annealed states of the emitter showed semiconducting behavior in accordance with the Fowler–Nordheim law. In case of an initially annealed emitter tip, the field emission current was found to increase monotonically with the light exposure, reversibly for shorter durations of a few minutes. The effect of long term (hourly) exposure of light resulted in the increase in the field emission current level nonlinearly with the exposure time. The current level did not come down to the original level even after switching off the light in contrast to the effect of short duration light exposure. The enhancement in the field emission current has been attributed to tunneling though the dangling bond states created by light exposure...

Morphology-controlled synthesis and enhanced energy product (BH)max of CoFe2O4 nanoparticles

High-performance cobalt ferrite nanoparticles (CoFe2O4 NPs) with controlled morphology were obtained by an economical and simple thermal decomposition technique. Cube-shaped CoFe2O4 NPs with different particle dimensions were achieved by precisely controlling the reaction refluxing time. The size-dependent magnetic properties were investigated and reported. The coercivity (Hc) of CoFe2O4 NPs increased with particle size upto single domain limit. Higher coercivity (Hc) values of 17 132 Oe and 3364 Oe with excellent remanent magnetization (Mr) values of 76.0 and 61.05 emu g−1 at 10 K and room temperature were obtained for CF-4 NPs (∼35 nm). The excellent remanent magnetization and high coercivity of CF-4 NPs led to a high energy product (BH)max of 2.41 MGOe (19.2 kJ m−3) at room temperature, which is the highest reported value to date for CoFe2O4 NPs to the best of our knowledge. The excellent magnetic properties indicated the capabilities of CoFe2O4 NPs in permanent magnets for current technological applications.

Controlled Zn1−xNixO nanostructures for an excellent humidity sensor and a plausible sensing mechanism

Here, we report on the chemi-resistive humidity sensing behavior of a Zn1−xNixO nanomaterial synthesized using a wet chemical method. At room temperature, the x = 0.10 sample shows excellent humidity sensitivity of 152% and a response/recovery time of 27/3 s within the 33–97% relative humidity (RH) range. The experimental data observed over the entire range of RH values can be well-fitted to a Freundlich adsorption isotherm model, which reveals two distinct water adsorption regimes. The obtained results suggest that the x = 0.10 sample has the highest adsorption strength. Theoretical humidity detection limits for the x = 0, 0.05 and 0.10 samples are found to be about 7.24% RH, 6.31% RH and 3.71% RH, respectively. The excellent humidity sensing observed using the ZnO and Ni doped ZnO nanostructures is attributed to a Grotthuss mechanism, considering the distribution of available adsorption sites. Therefore, Ni doped ZnO nanostructures synthesized via employing an economical wet chemical technique demonstrate promising capabilities to act as potential candidates for the fabrication of next-generation humidity sensors.