Multi-mode humidity sensing with water-soluble copper phthalocyanine for increased sensitivity and dynamic range

Abstract

Aqueous solubility of copper phthalocyanine-3,4′,4″,4″′-tetrasulfonic acid tetrasodium salt (CuPcTs) enables fabrication of flexible electronic devices by low cost inkjet printing. We (1) investigate water adsorption kinetics on CuPcTs for better understanding the effects of relative humidity (RH) on hydrophilic phthalocyanines, and (2) assess CuPcTs as a humidity-sensing material. Reaction models show that H2O undergoes 2-site adsorption which can be represented by a pair of sequentially-occurring pseudo-first order reactions. Using high frequency (300–700 THz) and low frequency (1–8 MHz) dielectric spectroscopy combined with gravimetric measurements and principal component analysis, we observe that significant opto-electrical changes in CuPcTs occur at RH ≈ 60%. The results suggest that rapid H2O adsorption takes place at hydrophilic sulfonyl/salt groups on domain surfaces at low RH, while slow adsorption and diffusion of H2O into CuPcTs crystallites leads to a mixed CuPcTs-H2O phase at RH > 60%, resulting in high frequency dielectric screening of the film by water and dissociation of Na+ from CuPc(SO3 −)4 ions. The CuPcTs-H2O interaction can be tracked using a combination of gravimetric, optical, and electrical sensing modes, enabling accurate ( ± 2.5%) sensing in the ~0–95% RH range with a detection limit of less than 0.1% RH.

Hierarchical TiO2:Cu2O Nanostructures for Gas/Vapor Sensing and CO2 Sequestration

“…39 Similarly, the lowest H 2 O detection limit, corresponding to ∼0.13% RH (0.03 Torr of H 2 O pressure), is also achieved by PAAm-functionalized TiO 2 :Cu 2 O films. This performance is comparable to the detection limits reported for other QCM-based RH sensors (15.76 ppm v corresponding to ∼0.05% RH), 40 multimodal optical/gravimetric sensing RH, 41 and QCM-based polymer mixture RH sensors. 42 Low detection limits and operability under a wide range of CO 2 and H 2 O partial pressures (0.1−22 Torr) suggest that TiO 2 :Cu 2 Obased gravimetric sensors are suitable for a wide variety of gas/ vapor detection and/or sequestration applications.…”

Light-Activated Hybrid Nanocomposite Film for Water and Oxygen Sensing

“…2 Under UV irradiation, SU-8 film with eight ZnO-infiltration synthesis cycles achieved the lowest detection limits corresponding to ∼0.004 Torr O 2 and ∼0.02% RH and showed potential for wide-range humidity sensing from 1 to 95% RH. The ZnOinfiltrated hybrid SU-8 film enabled significantly enhanced RH sensitivity (bottom panel) under a broad humidity range compared with the reported performances of other metal oxides (sensitive to 2% RH in 5−99% RH range), 45 graphene oxides (sensitive to 4% RH under 11−95% RH range), 46 organic small molecules (sensitivity of 2.5% in 0−95% RH range), 47 and conjugated polymers (sensitive to 1% RH in 33− 97% range). 48,49 In the dark, gravimetric responses of ZnO/SU-8 nanocomposite films were completely reversible after 1 h of gas/ vapor desorption.…”

Development of glucose biosensors using nanostructured composites

“…The ∆E p value of the PAA-CP/GPL-FePc/GOx-CH biosensor was 262 mV while that for the PAA-CP/GPL-FePc-CH biosensor was 316 mV. The results demonstrate the faster electron rate at the PAA-CP/GPL-FePc-CH biosensor electrode that was facilitated by GPL and FePc due to their large effective area and high conductivity(Muckley et al, 2017;Zagal et al, 1980). On immobilisation of GOx, the PAA-CP/GPL-FePc/GOx-CH biosensor electrode shows smaller ∆E p value indicates fast electron tansfer rate during the reaction.…”

“…The conducting hydrogels, PAA-CP/GPL-FePc-CH and PAA-CP/GPL-CH have shown two shoulders at 445 and 440 nm, and two peaks, 627 and 608 nm of CP, respectively ( Figure 5-4). These absorption spectra are ascribed to the π-π * transition of benzenoid ring and n-π * transition of benzenoid to quinoid, respectively (Chaiyo et al, 2018;Muckley et al, 2017). The Q band in the PAA-CP/GPL-FePc-CH spectrum is shifted bathochromically to 699 nm.…”

“…Modification the MPcs with four sulfuric group (SO 4 ) allows solubility in water and other solvents which significantly improve their deposition for catalysis applications (Zagal et al, 1980). These water-soluble metallophthalocyanines have attracted interest in a wide range of applications; for instance, Muckley and coworkers have utilised water-soluble copper phthalocyanine to develop a multi-mode humidity sensor (Muckley et al, 2017). High catalytic activity has been the most significant effective feature that has been invested to produce sensing devices based MPcs (Han et al, 2016;Mashazi et al, 2006;Ndiaye et al, 2016;Wang et al, 2005).…”