3D-printed millifluidic chip for synthesising plasmonic semiconductor nanocrystals as sensors substrate

ABSTRACT

In the past, plasmonics were always referred to as the collective oscillation of free electrons on metal surfaces such as gold (Au) and silver (Ag). This changed when plasmonic behaviour was experimentally demonstrated in semiconductors, i.e. self-doped copper sulfur, nanocrystals (Cu_2−xS NCs) in 2009. In fact, Cu_2−xS NC possesses different plasmonic behaviour than Au and Ag, in which the resonant condition is governed by another regime (free holes as the carriers) and its sensing capability has not yet been fully explored. In this contribution, the as-prepared (organic phase) Cu_2−xS NCs were transferred in water and were tested with glycerin-water mixtures and anions. The results showed that Cu_2−xS NC is very sensitive to the variation of refractive index in the surrounding environment. Furthermore, it was found that the plasmonic properties of these NCs are also very sensitive to the presence of anions. By taking the advantages of this “additional” effect, Cu_2−xS NC can be used as a potential substrate for the fabrication of sensor devices with enhanced sensitivity.

KEYWORDS:

• Plasmonics
• copper sulfide
• semiconductor nanocrystals
• millifluidic
• 3D-printed

Additional information

Funding

The work described in this paper was fully supported by the Research Grants Council of the HKSAR (Project No. PolyU [25200914]).

Notes on contributors

Wing Cheung Law

Dr Wing Cheung Law is currently an Assistant Professor in the Department of Industrial and Systems Engineering at The Hong Kong Polytechnic University. He obtained his BEng and MPhil degrees in Electronic Engineering from The Chinese University of Hong Kong in 2003 and 2005, respectively. He also received his Ph.D. degree in Electrical Engineering from the State University of New York at Buffalo, the USA in 2011. His research focuses on building nanoparticle-based biosensing systems and translating the bench-top setups into final products. He received two patents on designing surface plasmon resonance biosensors. He has published more than 90 peer-reviewed journals and served as a reviewer for 21 international journals.

Tai Lok Cheung

Mr Tai Lok Cheung is currently a Master student under the supervision of Dr Wing Cheung Law. His research work includes the synthesis and characterisation of novel nanomaterials for biosensing applications. He is also focused on the development of portable biosensor towards his MPhil thesis.

Nanxi Rao

Miss Nanxi Rao is a Research Assistant under the supervision of Dr Wing Cheung Law. Her research interests focus on the assessment of the toxicity of nanomaterials and the development of micro-scaffold for tissue engineering.