Naked-Eye Cadmium Sensor:  Using Chromoionophore Arrays of Langmuir−Blodgett Molecular Assemblies

Abstract

This study demonstrates the possibility of a reversible naked-eye detection method for submicromolar levels of cadmium(II) using the Langmuir-Blodgett (L-B) technique. Molecular assemblies of 4-n-dodecyl-6-(2-thiazolylazo)resorcinol are transferred on precleaned microscopic glass slides, to act as a sensing probe. Isotherm (pi-A) measurements were performed to ensure the films' structural rigidity and homogeneity during sensor fabrication. The sensor surface morphology was characterized using atomic force microscopy and scanning electron microscopy. The probe membrane exhibits visual color transition, forming a series of reddish-orange to pinkish-purple complexes with cadmium, over a wide concentration range (0.04-44.5 microM). Cadmium response kinetics and the changes in the sensors' intrinsic optical properties were monitored using absorption spectroscopy and further confirmed using X-ray photoelectron spectroscopy. A hybrid L-B film composite of poly(vinyl stearate) and poly(vinyl-N-octadecylcarbamate) were investigated for enhancing sensor performance. The sensor was tested for its practical approach to prove its cadmium selectivity and sensitivity amid common matrix constituents using synthetic mixtures and real water samples. Using the sensor strips, the respective lower limits of cadmium detection and quantification are 0.039 and 0.050 microM, as estimated from a normalized linear calibration plot.

Identification of the Cadmium-Inducible Hansenula polymorpha SEO1 Gene Promoter by Transcriptome Analysis and Its Application to Whole-Cell Heavy-Metal Detection Systems

“…Therefore, the development of monitoring systems for these metal ions in the environment has become increasingly important in order to prevent chronic exposure to these pollutants (2). As a response to this need, numerous biological systems and nonbiological sensors based on the emerging nanotechnology have been developed to monitor heavy metal contamination (38,43). In particular, biosensors that use unicellular microorganisms as analytical tools to monitor heavy metals have drawn attention because of several practical advantages (1): the large population size, rapid growth rate, low cost, and easy maintenance.…”

A review on detection of heavy metal ions in water – An electrochemical approach

“…In order to detect these most toxic metal ions many analytical techniques are being used namely atomic absorption spectroscopy (AAS) [81,82], atomic fluorescence spectroscopy (AFS) [83], inductively coupled plasma-mass spectroscopy (ICP-MS) [84], etc., [4,10,11,16,[85][86][87][88][89]. But these are expensive, bulky, time consuming [90] and require a well-trained analyst [91].…”

Environmental remediation and monitoring of cadmium

“…The optical sensor-based organic membrane for Cd 2+ was developed by applying 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA) on a cellulose triacetate membrane [61][62][63], 5,10,15,20-tetra(p-sulfonatophenyl) porphyrin [64] and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol on XAD-4 (Br-PADAP/XAD-4) membrane [65], and 1,2-bis-(quinoline-2-carboxamido)-4-chloro-benzene on PVC [66] and 1-(2-pyridylazo)-2-naphtol (PAN) on the tri-(2-ethylhexyl) phosphate (TEHP) plasticized cellulose-triacetate matrix.…”