Mukter Zaman

Recent advances in exploitation of nanomaterial for arsenic removal from water: a review

Recently, increasing research efforts have been made to exploit the enormous potential of nanotechnology and nanomaterial in the application of arsenic removal from water. As a result, there are myriad of types of nanomaterials being developed and studied for their arsenic removal capabilities. Nevertheless, challenges such as having a complete understanding of the material properties and removal mechanism make it difficult for researchers to engineer nanomaterials that are best suited for specific water treatment applications. In this review paper, a comprehensive review will be conducted on several selected categories of nanomaterials that possess promising prospects in arsenic removal application. The synthesis process, material properties, as well as arsenic removal performance and removal mechanisms of each of these nanomaterials will be discussed in detail. Fe-based nanomaterials, particularly iron oxide nanoparticles, have displayed advantages in arsenic removal due to their super-paramagnetic property. On the other hand, TiO2-based nanomaterials are the best candidates as photocatalytic arsenic removal agents, having been reported to have more than 200-fold increase in adsorption capacity under UV light irradiation. Zr-based nanomaterials have among the largest BET active area for adsorption-up to 630 m2 g-1-and it has been reported that amorphous ZrO2 performs better than crystalline ZrO2 nanoparticles, having about 1.77 times higher As(III) adsorption capacity. Although Cu-based nanomaterials are relatively uncommon as nano-adsorbents for arsenic in water, recent studies have demonstrated their potential in arsenic removal. CuO nanoparticles synthesized by Martinson et al were reported to have adsorption capacities up to 22.6 mg g-1 and 26.9 mg g-1 for As(V) and As(III) respectively. Among the nanomaterials that have been reviewed in this study, Mg-based nanomaterials were reported to have the highest maximum adsorption capacities for As(V) and As(III), at 378.79 mg g-1 and 643.84 mg g-1 respectively. By combining desired properties of different nanomaterials, composite nanomaterials can be made that have superior potential as efficient arsenic removal agents. Particularly, magnetic composite nanomaterials are interesting because the super-paramagnetic property, which allows efficient separation of nano-adsorbents in water, and high adsorption capacities, could be achieved simultaneously. For instance, Fe-Mn binary oxide nanowires have shown promising As(III) adsorption capacity at 171 mg g-1. Generally, nanomaterials used for arsenic removal face severe degradation in performance in the presence of competing ions in water, especially phosphate ions. This study will contribute to future research in developing nanomaterials used for arsenic removal that are highly efficient, environmentally friendly and cost-effective by providing a thorough, structured and detailed review on various nanomaterial candidates that have promising potential.

An Integrated Hybrid Energy Harvester for Autonomous Wireless Sensor Network Nodes

Profiling environmental parameter using a large number of spatially distributed wireless sensor network (WSN) NODEs is an extensive illustration of advanced modern technologies, but high power requirement for WSN NODEs limits the widespread deployment of these technologies. Currently, WSN NODEs are extensively powered up using batteries, but the battery has limitation of lifetime, power density, and environmental concerns. To overcome this issue, energy harvester (EH) is developed and presented in this paper. Solar-based EH has been identified as the most viable source of energy to be harvested for autonomous WSN NODEs. Besides, a novel chemical-based EH is reported as the potential secondary source for harvesting energy because of its uninterrupted availability. By integrating both solar-based EH and chemical-based EH, a hybrid energy harvester (HEH) is developed to power up WSN NODEs. Experimental results from the real-time deployment shows that, besides supporting the daily operation of WSN NODE and Router, the developed HEH is capable of producing a surplus of 971 mA·hr equivalent energy to be stored inside the storage for NODE and 528.24 mA·hr equivalent energy for Router, which is significantly enough for perpetual operation of autonomous WSN NODEs used in environmental parameter profiling.

Design and Fabrication of Low Voltage Silicon Trench MOS Barrier Schottky Rectifier for High Temperature Applications

This paper presents the design, fabrication, and characterization of 60V and 100V silicon Trench MOS Barrier Schottky (TMBS) rectifier. The devices were designed for switching power supplies operated in high temperature environment. Design considerations of silicon TMBS rectifiers are discussed in this paper. Trench structure design and trench oxide were improved to produce low reverse leakage current and high device performance. As a result, TMBS rectifiers with blocking voltage of up to 60V and 100V were successfully fabricated. The tradeoff between reverse leakage current and forward voltage drop are well controlled at high operating temperature (>75°C).

Recent advances in the design and development of radio frequency-based energy harvester for powering wireless sensors: a review

ABSTRACT Wireless sensor networks (WSNs) are spatially distributed sensor systems used to collect precise data from a large area of interest. WSN is usually deployed in the off-grid, and its widespread deployment is limited due to its requirement for the continuous and large amount of power. Energy harvesting has been recognized as a promising solution which has gained a lot of attention in recent years pertaining to enabling a self-sustainable operation of WSN. Radio Frequency (RF) is identified as an energy source that can be further used to harvest required energy for the WSN sensors. This paper outlines the motivation of RF energy harvesting for powering the WSN components. It is found that the rectenna circuit in RF harvester deals with very low amplitude of signals, and it requires further improvement in its feature and capabilities with reducing form factors. In this article, recent design and development consideration involved in rectenna circuit and corresponding performance trade-offs are being discussed. It also discusses the recent techniques involved in improving the overall power conversion efficiency of rectenna. The authors address the key challenging issues yet need to concentrate on further enhancements. This review will aid as a guide in the future, to develop an energy-efficient and high-performance RF harvester circuit, which needs to be taken to the next advance level.

Design and Implementation of Hybrid Micro Energy Harvester for Autonomous WSN Components

Successful deployment of Wireless Sensor Network (WSN) depends on the availability of power sources. Conventional battery-based WSN components has several drawbacks, such as limited life-span, bulky size and hazardous to the environment. Hence, energy harvesting from ambient sources attracts enormous attention. But energy harvesting depends on the availability of the ambient sources. In most cases energy harvesting from a single source is not enough to produce sufficient energy to power up WSN components. This paper describe about the design, and implementation consideration of a hybrid energy harvester for an autonomous sensing system. The sensing components of WSN are connected with the hybrid energy harvester on the same structure to generate required energy from the ambient environment such as solar and chemical reaction. As a case study, the power requirements of in-house developed WSN components [1] are measured. Based on the power requirement a hybrid energy harvester based autonomous system is designed [2], and a functional prototype of the system is implemented. In the implemented prototype, energy is being harvested from the ambient solar and chemical sources. From the evaluation of the developed system, it is found that powering WSN components, hybrid energy harvester produces an additional amount of 10491.93 J (equivalent to 2.91 Wh) of energy, which is capable to fill-up a 971 mA-hr storage in one day operation. This is enough for the WSN components to draw power subsequently, when there is not enough ambient sources available for next few days.

Design of MEMS Based Energy Harvester to Profile Environmental Parameter Using Autonomous WSN Components

With the rapid development on micro electro mechanical system (MEMS) and wireless transmission technology, wireless sensor networks (WSN) are becoming an emerging technology with a number of potential applications. One such application is the monitoring of agricultural environmental parameter. Such an application requires an infinite-life power source that will harvest energy continuously from the ambient environment. This paper describe about the design, and development consideration of an energy harvester for an autonomous sensing system. The sensing components of WSN are connected with the energy harvester on the same structure to generate required energy from the ambient environment. As a case study, the power requirement by MIMOS Berhad [1] developed WSN components are measured from real time deployment. Based on the power requirement an autonomous system is designed (patent granted [2]) and proof of concept (POC) of the system is implemented. The POC shows from 1 cm2 area of the energy harvester a potential difference of 0.6 V and current of 0.25mA can be achieved. These results shows, by cascading several unit area of the energy harvester and integrating it with WSN components, it is possible to achieve autonomous WSN system, which is very essential for realistic deployment of WSN.

The Effect on Physical, Electrical and Structural Parameters of RF Sputtered Molybdenum Thin Film

In this study, the physical, electrical, and structural parameter on radio frequency (RF) sputtered molybdenum thin film is investigated as a function of two deposition parameters: rf power, and argon (Ar) pressure. Films are sputtered onto the substrates nominally held in room temperature in a RF sputtering system at partial argon (Ar) pressure. A number of 10 films are deposited at 8 sccm of Ar pressure while varying the rf power from 90 to 360 watt. Besides, another set of 7 films are deposited at 240 watt RF power while varying the Ar pressure from 8 to 32 watts. All the films are characterized using FESEM, AFM, XRD, and four points probe. The analysis results substantiate that, to fabricate a low resistive thin layer of molybdenum (Mo) both sputtering power, and deposition time Ar pressure plays significant rules. It is found that, with the increase of the RF power (90 to 280 watt) the deposition rate increase from 1.2 A0/sec to 4.4 A0/sec. But at a RF power higher than 280 watt the deposition rate saturated and it does not increase as linear as before. Also resistivity continuously decreases as the RF power increases from 90 watt up to 270 watt, after that the resistivity remain almost same regardless the RF power increased. Besides, by varying the Ar pressure it is found that with the increase of the Ar pressure the deposition rate increase until 20 sccm (up to 2.4 A0/sec). With further increase of the Ar pressure deposition rate start reducing and reached 2.1 A0/sec at 32 sccm. Based on the above investigation and analysis optimized film is deposited and further analyzed. The surface roughness is analyzed using AFM characterization tool and found 27.4519 nm. The FESEM and XRD analysis along with the resistivity of the film is used to measure the strain of the deposited film and found a strain of less than 0.01% on the optimized film, which is essential for MEMS/NEMS device fabrication and energy harvesting applications.

ToF measurement based novel top edge detection algorithm for a smart security system

This paper describes a security system capable of identifying the presence of moving object using ultrasonic sensor, without human intervention. A constrained optimization of the Time of Flight (ToF) technique is employed to obtain the reflected pulses that are easily detectable by means of threshold comparator. Converting the ultrasonic sensors output into predefined value based on ToF and our novel Top Edge Detection (TED) algorithm, the system is able to fix a position from where CMOS image capturing sensor can capture an instance of image of the object.