The Langmuir−Blodgett deposition of organically passivated gold nanoparticles is reported. A monolayer of these particles has been incorporated into a metal−insulator−semiconductor (MIS) structure. The MIS device exhibits a hysteresis in its capacitance versus voltage characteristic, the magnitude of which is dependent on the voltage sweep conditions. Charge storage in the layer of nanoparticles is thought to be responsible for this effect.
We demonstrate a nonvolatile electrically erasable programmable read-only memory device using gold nanoparticles as charge storage elements deposited at room temperature by chemical processing. The nanoparticles are deposited over a thermal silicon dioxide layer that insulates them from the device silicon channel. An organic insulator deposited by the Langmuir–Blodget technique at room temperature separates the aluminum gate electrode from the nanoparticles. The device exhibits significant threshold voltage shifts after application of low-voltage pulses (⩽±6 V) to the gate and has nonvolatile retention time characteristics.
In this work, we demonstrate a MISFET memory device that incorporates a monolayer of Langmuir-Blodgett (LB) deposited gold nanoparticles as floating gate charge storage elements. The FET device is fabricated on a SOI substrate using conventional silicon processing. The nanoparticle layer is separated from the channel area of the FET with a 5 nm thermal SiO2 layer and is isolated from Al gate contact with a LB-deposited organic insulator layer. The memory effect is tested using voltage pulses on the gate of the device and monitored through drain current measurements. The nanocrystals can be charged either from the channel through the thermal oxide layer by applying pulses smaller than 5 V or from the gate through the organic insulator for higher voltage depending on the pulse duration.
The presence of arsenic in groundwater and other drinking water sources presents a notable public health concern. Although the utilization of iron oxide nanomaterials as arsenic adsorbents has shown promising results in batch experiments, few have succeeded in using nanomaterials in filter setups. In this study, the performance of nanomaterials, supported on sand, was first compared for arsenic adsorption by conducting continuous flow experiments. Iron oxide nanoparticles (IONPs) were prepared with different synthetic methodologies to control the degree of agglomeration. IONPs were prepared by thermal decomposition or coprecipitation and compared with commercially available IONPs. Electron microscopy was used to characterize the degree of agglomeration of the pristine materials after deposition onto the sand. The column experiments showed that IONPs that presented less agglomeration and were well dispersed over the sand had a tendency to be released during water treatment. To overcome this implementation challenge, we proposed the use of clusters of iron oxide nanoparticles (cIONPs), synthesized by a solvothermal methodology, which was explored. An isotherm experiment was also conducted to determine the arsenic adsorption capacities of the iron oxide nanomaterials. cIONPs showed higher adsorption capacities (121.4 mg/g) than the other IONPs (11.1, 6.6, and 0.6 mg/g for thermal decomposition, coprecipitation, and commercially available IONPs, respectively), without the implementation issues presented by IONPs. Our results show that the use of clusters of nanoparticles of other compositions opens up the possibilities for multiple water remediation applications.
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