Dendrimer Modified Silica Nanoparticles as Fluorescent Chemosensors for the Detection of Copper and Cyanide Ions

<p>A series of silica nanoparticle-based fluorescent chemosensors were synthesized for the sensitive and selective detection of Cu²⁺ions in aqueous solution and subsequent CN^- ion detection. Silica nanoparticles (SNP) were modified with branching polyamidoamine (PAMAM) dendrimers, which function as selective turn-off Cu²⁺ion chelators and platforms for the attachment of rhodamine isothiocyanate (RITC) or fluorescein isothiocyanate (FITC) fluorescent dyes. In the presence of Cu²⁺ions, the emission of the fluorescent dye is quenched by Forster resonance energy transfer (FRET) and is dependent upon dendrimer generation, pH, fluorescent dye, and surface charge. The quenching effectiveness was analyzed by Stern-Volmer quenching analysis and increased with dendrimer generation up to G4, yielding a Stern-Volmer quenching constant of 14 (±2) x 10⁵M^-1and a limit of detection of 0.2 µM Cu²⁺ under optimal conditions (SNPG4-FITC). Furthermore, the fluorescence can be fully restored by the subsequent addition of CN^- ions, which is surprisingly effective compared to other strong anion chelators like EDTA and azide at low concentrations, reaching a turn-on detection limit of 1 µM CN^- (SNPG4-FITC). The turn-off, turn-on fluorescent chemosensing systems were also used as FRET sensors for 8-Anilino-1-naphthalenesulfonic acid (ANS) to prove the applicability of the systems as small organic molecule sensors. In the future, the same SNPGx-Dye sensing system can be customized to sense additional analytes like polycyclic aromatic hydrocarbons, explosives, and amino acids.</p>

Name thesis:degree_name

Master of Science in Chemistry

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemistry

Year dc:date.available

2016

Author dc:creator

• Luhrs, Alicia

Contributors dc:contributor

• Lawrence Margerum
• William Melaugh
• Ryan West

• silica nanoparticles
• fluorescent chemosensor
• dendrimer
• FRET
• copper
• Analytical Chemistry
• Inorganic Chemistry

Repository record dc:identifier

https://repository.usfca.edu/thes/175

OAI identifier oai:identifier

oai:repository.usfca.edu:thes-1214