Self-assembled monolayers as selective filters for chemical sensors

Abstract

The lateral electrical conductivity of gold layers with thickness in the nanometre range was found to decrease due to adsorption of mercury, water, iodine and sulphuric compounds onto the gold surface. A self-assembled monolayer of hexadecanethiol, deposited on the gold surface, blocked the effects of water and volatile sulphuric compounds on the lateral conductivity of the gold layers, but does not block the effects of iodine and mercury. The results indicate a selective permeability of hexadecanethiol monolayers for mercury vapour, thus providing a method for development of ultrathin filters for chemical sensors.

SPR investigation of mercury reduction and oxidation on thin gold electrodes

“…The condensation of the gold film due to interaction with mercury suggests an attraction of atoms of these metals. It corresponds to literature data: an affinity of mercury to gold is well known and widely used for preconcentration of mercury vapor and as a receptor in chemical sensors for mercury vapor [17][18][19][20][21].…”

Ordered Monolayer Gold Nano-urchin Structures and Their Size Induced Control for High Gas Sensing Performance

“…Some of the issues with these techniques are arisen as they are based on Hg 0 undergoing absorption/emission at 253.7 nm wavelength which can cause the occurrence of undesired photochemical reactions in the industrial effluent streams which contain other interfering gas species that are excited by the same UV wavelength. Furthermore, these systems are costly, bulky, require specialized sample collection and gas conditioning as well as being associated with many challenges before they can be employed as online sensors 28 37 38 39 40 . In addition to the aforementioned limitation of the analytical instruments, the sampling requirements associated with the Ontario Hydro (OH) or Appendix K methods prior to detection are also expensive, require skilled operators and can have up to 2-week turnaround time thus providing no real-time data 41 .…”

Gold nanospikes based microsensor as a highly accurate mercury emission monitoring system

“…To test the long-term performance of the Au control and nanospikes based QCMs, both were tested in a specially designed chamber and exposed to different Hg 0 vapor concentrations (C 1 = 1.02 mg/m 3 , C 2 = 1.87 mg/m 3 , C 3 = 3.65 mg/m 3 , C 4 = 5.70 mg/m 3 and C 5 = 10.55 mg/m 3 ± 0.05 mg/m 3 ) in the presence of six interferent gases (listed in Table 1 ) at an operating temperature of 101°C for a continuous period of 127 days. The interferent gas species and their concentrations were chosen to include VOCs that are present in industrial flue gases 27 28 29 and/or known to have high affinity towards Au surfaces 30 31 32 33 34 35 36 37 38 39 40 . The long-term testing was designed to simulate the process conditions common found in minerals processing industries, such as those of an alumina refinery.…”

“…Both sets of sensors were tested in a specially designed sensor chamber. The sensors were tested towards Hg 0 vapor in the presence of additional interferent gases (listed in Table 1 ) including volatile organic compounds (VOCs) that are known to have high affinity with Au 30 31 32 33 34 35 36 37 38 39 40 or to be present in most industrial flue gases 27 28 29 . Throughout the experiments, the total gas flow rate (N 2 + Hg 0 , Hg 0 + interferent gas species or N 2 alone) was kept constant at 200 sccm using a specially developed multi-channel gas delivery system, employing mass flow controllers (MKS instruments, Inc. USA).…”