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- Heinz, D., et al.
(author)
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GaInN Quantum Wells as Optochemical Transducers for Chemical Sensors and Biosensors
- 2017
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In: IEEE Journal of Selected Topics in Quantum Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-4542 .- 1077-260X. ; 23:2, s. 15-23
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Journal article (peer-reviewed)abstract
- In this paper, investigations on gallium indium nitride (GaInN) quantum well structures as optochemical transducers in (bio) chemical sensing are presented. In contrast to the conventional electrical read-out of III-nitride-based sensors, a purely optical photoluminescence read-out is performed. A significant spectral shift of the quantum well photoluminescence is observed with varying surface modification. The spectral photoluminescence shift can be attributed to an externally induced quantum confined Stark effect caused by the adsorbed species deposited on the quantum well surface. In order to improve the sensitivity of the transducer elements, different chemical surface treatments are studied. In particular, optical sensing experiments with reducing and oxidizing gases are performed in order to investigate the quantum well photoluminescence response. Additionally, optical investigations of the iron-storage molecule ferritinwith varying iron load are presented. The iron load of this molecule is generally considered as a superior biomarker for severe illnesses, such as Alzheimer's disease. In contrast to conventional fluorescent labels, GaInN quantum wells provide a much more stable luminescence signal, and hence, are promising candidates for next generation bioanalytical sensor structures.
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- Busi, KB, et al.
(author)
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Surface Ligand Influences the Cu Nanoclusters as a Dual Sensing Optical Probe for Localized pH Environment and Fluoride Ion
- 2023
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In: Nanomaterials (Basel, Switzerland). - : MDPI AG. - 2079-4991. ; 13:3
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Journal article (peer-reviewed)abstract
- Functional metal nanomaterials, especially in the nanocluster (NC) size regime, with strong fluorescence, aqueous colloidal stability, and low toxicity, necessitate their application potential in biology and environmental science. Here, we successfully report a simple cost-effective method for red-/green-color-emitting protein/amino-acid-mediated Cu NCs in an aqueous medium. As-synthesized Cu NCs were characterized through UV-Vis absorption spectroscopy, fluorescence spectroscopy, time-resolved photoluminescence, dynamic light scattering, zeta potential, transmission electron microscopy and X-ray photoelectron spectroscopy. The optical properties of both Cu NCs responded linearly to the variation in pH in the neutral and alkaline ranges, and a robust pH reversible nature (between pH 7 and 11) was observed that could be extended to rapid, localized pH sensor development. However, a contrasting pH response nature between protein–Cu NCs and amino acid–Cu NCs was recorded. The alteration in protein secondary structure and strong binding nature of the surfactants were suggested to explain this behavior. Furthermore, we investigated their use as an efficient optical probe for fluoride ion detection. The limit of detection for protein–Cu NCs is 6.74 µM, whereas the limit of detection for amino acid–Cu NCs is 4.67 µM. Thus, it is anticipated that ultrasmall Cu NCs will exhibit promise in biological and environmental sensing applications.
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