Localized Surface Plasmon Resonance Decorated with Carbon Quantum Dots and Triangular Ag Nanoparticles for Chlorophyll Detection

Abstract

This paper demonstrates carbon quantum dots (CQDs) with triangular silver nanoparticles (AgNPs) as the sensing materials of localized surface plasmon resonance (LSPR) sensors for chlorophyll detection. The CQDs and AgNPs were prepared by a one-step hydrothermal process and a direct chemical reduction process, respectively. FTIR analysis shows that a CQD consists of NH2, OH, and COOH functional groups. The appearance of C=O and NH2 at 399.5 eV and 529.6 eV in XPS analysis indicates that functional groups are available for adsorption sites for chlorophyll interaction. A AgNP–CQD composite was coated on the glass slide surface using (3-aminopropyl) triethoxysilane (APTES) as a coupling agent and acted as the active sensing layer for chlorophyll detection. In LSPR sensing, the linear response detection for AgNP–CQD demonstrates R2 = 0.9581 and a sensitivity of 0.80 nm ppm−1, with a detection limit of 4.71 ppm ranging from 0.2 to 10.0 ppm. Meanwhile, a AgNP shows a linear response of R2 = 0.1541 and a sensitivity of 0.25 nm ppm−1, with the detection limit of 52.76 ppm upon exposure to chlorophyll. Based on these results, the AgNP–CQD composite shows a better linearity response and a higher sensitivity than bare AgNPs when exposed to chlorophyll, highlighting the potential of AgNP–CQD as a sensing material in this study.

A Self-Referenced Refractive Index Sensor Based on Gold Nanoislands

“…Nanolithography techniques, such as electron beam lithography [ 19 ] and nanoimprint lithography [ 20 ], allow controlled positioning and dimensioning of nanostructures according to a specific pattern; however, they typically require multiple processing steps and complex, expensive processing facilities. On the other hand, lithography-free nanofabrication processes, such as colloidal nanoparticle deposition [ 21 , 22 , 23 , 24 ] and dewetting [ 25 , 26 , 27 , 28 , 29 , 30 ], typically result in a low-ordered or random distribution of nanoparticles, which exhibit significant size dispersion; nevertheless, they are simpler and lower-cost fabrication alternatives. In particular, thermal dewetting by annealing of thin metal films [ 25 , 26 , 27 , 28 , 29 , 30 ] is one of the easiest and cheapest methods to produce metal nanostructures on solid substrates.…”