Here, we discuss an interesting concept that brings an added flexibility in chemo/bio sensing. We
present system that can be switched photonically between two states, only one of which exhibits ion-binding
behaviour. The system is based on molecular photoswitch spiropyran, which is probably the
most studied compound exhibiting above characteristics. Upon irradiation with UV light the passive
spiropyran (SP) molecule undergoes a heterocyclic ring cleavage that results with the formation of the
merocyanine (MC) which is zwitterionic form capable of ion binding. In contrast to the uncharged and
colourless spiropyran form, the merocyanine form is highly charged and can be utilized as ligand for
other charged species. Moreover, it is strongly coloured, and the colour tells us which form is present.
In addition it provides interesting information about the immediate environment of the merocyanine
binding site (e.g. polarity, presence of certain ions etc.). In this work, we present a SP-based system in
which SP is immobilized and protected within a polymeric matrix. Such system may be used for
detection of metal ions in highly polar solvents, e.g. water. The response characteristics and kinetics of
MC-Cr3+ complex formation and SP-MC switching within the polymer matrix have been determined.
Simple light emitting diodes (LEDs) have been employed for photoswitching and colorimetric
measurement of SP-MC switching and MC-Cr3+ complex formation as light sources and detectors.
KEYWORDS: Sensors, Microfluidics, Global system for mobile communications, Calibration, Photodiodes, Telecommunications, Prototyping, Light emitting diodes, Liquids, Absorbance
This work describes the ongoing development of an autonomous platform for the measurement of phosphate levels in river water. This device is designed to operate unassisted for one year, taking a measurement every hour and relaying the result to a laptop computer. A first generation prototype has already been developed and successfully field tested. The system contains the sampling, chemical storage, fluid handling, colorimetric data acquisition and waste storage capabilities necessary to perform the phosphate measurement. In addition to this, the device has the embedded control, GSM communications system and power supply to allow independent operation. The entire system is placed inside a compact and rugged enclosure. Further work discussed here builds on the successes of the prototype design to deliver a system capable of one full year of operation. The second generation system has been built from the ground up. Although identical in operation to the prototype its design has a greater emphasis on power efficient components and power management to allow for a longer lifetime. Other improvements include an automated two-point calibration to compensate for drift and a more rugged design to further increase the lifetime of the device.
We outline a system for monitoring methane over the internet using a simple wireless sensor network. The system was developed for use at a capped landfill site which contains municipal solid waste. The sensor nodes use commercially available metal oxide semiconductor gas sensors to monitor and allow for a near real-time monitoring of gas emissions. This system is intended to complement the work of personnel who have to physically take the measurement using hand-held infrared instrument. We also outline preliminary testing of this system.
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