Degree Type


Date of Award


Degree Name

Master of Science


Agricultural and Biosystems Engineering

First Advisor

Chenxu Yu


In this thesis, filed-deployable nano sensors for onsite detection of nitrite and microorganisms were developed. The colorimetric nitrite ion sensor was designed utilizing 4-aminothiophenol (4-ATP) modified gold nanorods (GNR). In the presence of nitrite ions, the deamination reaction was induced by heating the 4-ATP modified GNR in ethanol solution, resulting in the reduction of the GNR surface charges, which led to aggregation of GNRs and a colorimetric response that was quantitatively correlated to the concentration of nitrite ions. This simple assay was rapid (less than 10 minutes) and highly sensitive (< 1 ppm of nitrite), it can be used for rapid monitoring of drinking water quality. Anisotropic nanoparticles (i.e., silver nanocubes, gold nanorods) based SERS molecular probe were also designed and fabricated for the rapid and specific detection of bacterial targets in a test-in-a-tube platform utilizing a novel dual-recognition mechanism. The probes were synthesized by covalently attaching Raman tags and bacteria-specific antibodies to the surface of silver nanocubes. Specific binding between the probes and bacterial targets ensured surface enhanced Raman spectroscopic (SERS) signatures of the targets to be observed alongside with the SERS signals of the Raman tags. The assessment through the dual signals (superimposed target and tag Raman signatures) established a specific recognition of the targets in a single step, no washing/separation steps were needed to separate target-bound probes from unbound ones, because unbound probes only yield tag signatures, and could easily be distinguished from the target-bound ones. The dual-recognition protocol implemented with a portable Raman spectrometer would become an easy-to-use, field-deployable spectroscopic sensor for onsite detection of pathogenic microorganisms.


Copyright Owner

Nan Xiao



Date Available


File Format


File Size

66 pages