Gas-Phase Selective Adsorption on Functional Monolayers Immobilized on a Highly Sensitive Quartz-Crystal Microbalance

Abstract

Self-assembled monolayers of alkanethiols having functional groups (HS(CH2)10X; X = −H, −COOH, −CONH2, −NH2) were immobilized on an Au electrode of a quartz-crystal microbalance (QCM), and binding kinetics of acetic acid molecules from the gas phase were studied from time courses of frequency decreases (mass increases) of the QCM. A highly sensitive, 63 MHz overtone frequency of a conventional 9 MHz AT-cut QCM was developed to detect monolayer adsorption of small molecules such as acetic acid. Acetic acid molecules are adsorbed onto the −CONH2 membrane as a Langmuir-type monolayer; however, they tend to be adsorbed as multilayers onto the −COOH and −NH2 membranes. Acetic acid was hardly adsorbed onto the simple alkane membrane (−H membrane). The binding ability of the −COOH membrane to acetic acid molecules was reduced compared with that of the −CONH2 membrane due to the intramembranous hydrogen bond in the former.

Cation recognition by self-assembled monolayers of oriented helical peptides having a crown ether unit

“…The impedance spectra were collected at a potential of Ϫ0.50 V in a frequency range of 100 kHz to 0.01 Hz with an ac potential of 5 mV. Titration with metal chlorides was performed in a background electrolyte of [Et 4 NCl] ϭ 0.1M.…”

“…The SAMs, which are composed of compounds having a functional group, are interesting especially in the application fields of biomaterials, 2,3 and microelectronics. 4,5 When the functional group recognizes a specific molecule, the modified gold will be used as an electrode for a chemical sensing device. 6 The molecular recognition process can be detected sensibly by IR spectroscopy, 3 quartz crystal microbalance (QCM), 4,5 surface plasmon resonance (SPR), 6 and electrochemical measurements.…”

Dynamic Analyses on Induced-Fit Gaseous Guest Binding to Organic Crystals with a Quartz-Crystal Microbalance

“…If there is simple equimolar binding then the plot would be a straight line with a slope of k 1 (binding rate constant) and an intercept of k À1 (dissociation rate constant). [38] However, t À1 values increased abruptly above a certain threshold concentration, that is, the values depend on the multiplied term of the guest concentration. This behavior would be also attributed to cooperativity on guest binding.…”

“…[37] Recently, we combined a QCM technique and a flow cell to detect the molecular recognition of gaseous guests on a functionalized monolayer. [38] In this paper, we report the dynamic studies of gaseous guest binding to the apohost crystals immobilized on a QCM (see Figure 1). We chose crystals of anthracene-bis(resorcinol) (1) as the host; it forms molecular sheets held together by an extensive hydrogen-bonded network and has large (% 10 ) cavities similar to those of organic zeolites.…”

Detection of Volatile Organic Compounds by Self-assembled Monolayer Coated Sensor Array with Concentration-independent Fingerprints

“…, affinities and kinetics of VOCs adsorption onto various functionalized surfaces can be analyzed with different isotherms and kinetic models. To date, a number of attempts for gas sensing with acoustic wave resonators, particularly surface acoustic wave (SAW) device 24 25 26 27 , quartz crystal microbalance (QCM) 28 29 30 31 32 33 and cantilever 34 35 have been made with remarkable results. However, the operation frequencies of those devices are limited (below GHz), and could not meet the demand of high sensitivity for vapor detections at trace levels which is normally required for the analysis of the adsorption affinity and kinetics parameters.…”