Detection of Zn in water using novel functionalised planar microwave sensors

Abstract

Metal pollution in aquatic environments has attracted global attention. Current methods are not able to monitor water quality in-situ at low-cost. This paper reports on a novel approach for detecting changes in the concentration of zinc in water using electrical and a microwave sensor method, adopting two planar sensors: one was functionalised with a screen-printed β-Bi 2 O 3 based coating, while the other was uncoated. Results show that both electrical and the microwave sensor responses were dependent on the presence and concentration of Zn in water with R 2 = 0.93-0.99. The functionalised sensor with a 60 μm thick β-Bi 2 O 3 based film offers improved performance compared with both uncoated and functionalised sensors with 40 µm thick coating for detecting the changes of Zn concentrations in water for low levels (100 and 500 µg/L). This novel sensing system could be a cost-effective alternative to the current offline methods.

Microwave Sensors for In Situ Monitoring of Trace Metals in Polluted Water

“…Initial experiments demonstrated the feasibility of measuring water samples by dipping the waterproofed sensors in water samples. Figure 8 compares the signal response measured by placing 400 μL of the water sample onto the sensor (black line) (as described by [93]) and submerging the sensors into a DW sample (red line) using the adapted eightpair IDE sensor directly probing the water sample, keeping in mind the possibility to move to the real-world environment and performing in situ measurements. The signal response changes from using the 400 μL method described in previous works, probably due to the propagation of the EM waves in a diverse volume.…”

Real-Time Water Quality Monitoring with Chemical Sensors

“…The sensing response as S 11 can be determined by direct contact between the material and the analyte under test, which changes the permittivity of each component, and the consequent overall complex permittivity changes. The improvement can be associated with the increase of material thickness as well as the composition itself [ 66 ].…”

“… Microwave sensor functionalized with Bi 2 O 3 -based coating for the detection of Zn in water ( left ), and the dependence of the reflected signal (S 11 ) response on Zn concentration ( right ). Reproduced with permission from [ 66 ] © Elsevier. …”

Functionalised microwave sensors for real-time monitoring of copper and zinc concentration in mining-impacted water

“…Screen-printing technology can be used to place thick films on planar EM sensors. The produced coatings have the advantage of being repeatable, reusable and can be prepared using a mixture of various materials, increasing the specific detection of compounds in complex water matrices (Frau et al 2019b).…”

“…Consequently, the sensing performance was improved by a modification of the spectral response and the increment of specificity (Bernou et al 2000). Notably, the EM waves interact with each part of the sensor and the sensing response will depend on the permittivity change of each component, such as the sensor itself, the coating, the coating thickness, the chelated metal ions on the coating and the sample under test (Frau et al 2019a). The f-EM sensors are not only detecting the metals which are chelated on the L-CyChBCZ substrate, and which generate a variation in the spectral response, but also the overall change in the sample under test.…”