Optical imaging has emerged to be the gateway to the world of biology in the past several decades. Various classes of optical probes such as fluorescent molecules, semiconductor quantum dots and other hybrid materials have been developed to image biological systems with unprecedented detail. However, these probes have faced several challenges in mitigating problems such as low quantum yield, considerable photobleaching and a strong autofluorescence.
To overcome these inherent shortcomings we propose the engineering of upconversion nanoparticles (UCNP). Furthermore, these UCNP’s can be converted to unique single-nanoparticle lasers by introducing an appropriate gain medium for embedding and a plasmonic core. The sequential absorption of low energy photons provides UCNP’s order of magnitude more efficient than other multiphoton processes, and the gain medium enhances the plasmonic enhancement thereby increasing the quantum yield drastically, and also narrowing the emission profile considerably.
The presence of the plasmonic core also renders the nanoprobes the functionality to be used as dual surface-enhanced Raman spectroscopy (SERS) agents. The single-molecule detection limit of SERS combined with the narrow emission profile of the upconversion nanoprobes makes it efficient for multiplexed imaging of complex biological systems. We propose a new design that facilitates the formation of lanthanoid doped upconversion nanoparticles complexed with plasmonic nanoparticles for ensuring luminescent enhancement and consistent SERS measurements. We envisage that these surface engineered nano-constructs will act as highly stable, robust, biocompatible and efficient platforms for Biological Imaging and other applications using both SERS and enhanced luminescence of UCNP’s. To use it as an efficient probing tool, the developed UCNP’s will be functionalized with engineered synthetic biomolecules through the spontaneous biological conjugation method. These functionalized UCNP’s will be directly applied into AC-EHD integrated nano-bioengineered chips for single-molecule detection of clinically important biomarkers.
These developed UCNP’s could be effectively utilized as highly sensitive detection probes as well as imaging tools. This work shall have huge potential to use these imaging probes in early diagnostics, especially single molecule detections. The project is expected to lead to high-impact publications, patents and clinical collaborations.