Fabrication of Selective Sensors for Hg 2+ Traces in Water Using Graphene Decorated with Metal Nanoclusters

摘要: Mercury metal is released into water by different sources including sewage industrial waste, thus, it can enter human food chain. It considered one of the most harmful pollutant heavy metals since non-biodegradable, and to body means direct consumption (for example, through drinking water), absorption skin, respiratory system. Exposure mercury cause severe effects on health such as brain damage, kidney failure, damage in nervous system, birth defects, chromosome breakage, paralysis [1, 2]. The United Nation Environment Program (UNEP) assessed annual quantity 4400-7500 tons [3]. In addition, International World Health Organization regulated maximum allowed amount ions (Hg2+) 6 ppb [4]. Nevertheless, previous studies estimated inorganic Hg2+ 0.5 [5]. Therefore, development sensitive, selective, reliable, cost effective sensors needed for medical diagnostic, quality control industry, well environment monitoring. this work, we present novel conductometric based graphene Au nanoclusters that are highly selective ions. Electrical electrodes were deposited surface thermal evaporation. produced sputtering inert gas condensation technique inside an ultra-high vacuum chamber, they self-assembled graphene. To best our knowledge, reported here first utilized detection traces water. These exceedingly sensitive ions, therefore, have potential be applied practical life applications. Gold system consists three main chambers (source, mass filter, deposition chambers) pumped initially a base pressure 10-8 mbar using two turbo pumps. A gold target purity 99.99% (Testbourne ltd, UK) was fixed water-cooled magnetron sputter head. Plasma generated source chamber argon (Ar) gas, used from its dc discharge type. supplied Ar also condense sputtered material forming nanoclusters, create gradient between enables formed travel chamber. Each sensor fabricated (1 cm × 1 cm) commercial layer SiO2/doped-Si substrate (thickness SiO2 285 nm, Si p-type with resistivity 0.001-0.005 ohm.cm). Interdigitated parallel (with electrode separation 100 μm) evaporation Torr evaporator shadow mask [6]. Two batches tested work: i) only, ii) percolating films each has thickness 5 nm. For nanocluster deposition, sample cryostat finger. Nanocluster rate measured quartz crystal monitor (QCM) facing beam motorized linear translator. Next, QCM removed away sample, surface. Sensitivity measurements performed solutions concentrations (0.05, 0.1, 0.3, 0.6, 3, 6, 20, 40, 60 ppb). selectivity 0.6 following ions: Cr2+, Cd2+, Cu2+, Co2+, Fe2+, Zn2+, K+. results reveal evidently enhanced nanoclusters. sensitivity decorated higher than made which could assigned high binding affinity [7, 8]. This explained qualitatively bearing mind investigated energy (under consideration work) either or Upon investigating graphene, highest compared other (Cr2+, Fe3+, K+), exhibit slightly lower thus their signals very comparative [8]. nanostructures found large due [7]. work [9], makes graphene-Au sensing mechanism graphene-based summarized follows: exposure decreases electron concentration n-type conductance decreases. Decoration creates scattering centers increase diffusive electrical conductance. Adsorption causes further decrease conductance, implies sensor. conclusion, below minimum limit set States Environmental Protection Agency. small size easy carry outdoor low power requirements, field References [1] W. Chemnasiri, F.E. Hernandez. nanorod-based functionalized glass substrates, Sensors Actuators B: Chemical 173 (2012) 322-328. [2] Y. Li, H. Huang, X. Su. Highly fluorescent (II) ion layer-by-layer water-soluble conjugated polymer, 188 (2013) 772-777. [3] B. Wang, S. Zhuo, L. Chen, Zhang. Fluorescent quantum dot nanoprobes Spectrochimica Acta Part A: Molecular Biomolecular Spectroscopy 131 (2014) 384-387. [4] WHO. Guidelines drinking-water quality. Fourth edition ed., Organization, 2011. [5] E. U.S. Drinking Water Contaminants. http://water.epa.gov/drink/contaminants/index.cfm#list, [6] A.I. Ayesh. Electronic transport Pd devices, Applied Physics Letters 98 (2011) 133108. [7] Z. Liu, P.C. Searson. Single Nanoporous Nanowire Sensors, Journal Physical Chemistry B 110 (2006) 4318-4322. [8] C. Yu, Guo, N. Yan, Xu, G. Fang, Liu. Ultrasensitive modified Communications 49 6492-6494. [9] S.A. Siddiqui, Bouarissa, T. Rasheed, M.S. Al-Assiri. Quantum chemical study interaction elemental Hg neutral, anionic cationic Aun (n = 1-6) clusters, Materials Research Bulletin 48 995–1002.