Selective Gold-Nanoparticle-Based “Turn-On” Fluorescent Sensors for the Detection of Cu(II) and Pb(II) in Aqueous Solution

A procedure has been developed to detect Hg(II) ions in aqueous solutions using gold-nanoparticles-based sensors. Rhodamine B (RB) molecules are highly fluorescent in solution, however their fluorescence decreases significantly when chelated to gold-nanoparticles (AuNP). When RB-AuNP molecules are in solution with 2+ metal ions, the RB molecules are released from AuNP which results in a turn-on fluorescence. This can be used to quantify the amount of 2+ metal ions in solution. Further modification of the ligands and reaction conditions increase the RB’s affinity for Hg(II) ions during the reaction. The end result is a highly-selective chemosensor with several applications.This experiment will focus on modifying the ligands and the reaction conditions to increase the affinity for Cu(II) ions and Pb(II) ions respectively, rather than Hg(II) ions. Properties of the AuNPs will also be investigated, including stability, size consistency, and preparation time. The purpose for these modifications is to develop a technique using AuNPs to detect metal ions in solution while decreasing hazardous waste and minimizing time, to allow this procedure to be performed as an analytical chemistry laboratory assignment.

Detecting Achetylcholinesterase Inactivity Caused by Low Levels of Organophosphorous Pesticides using Gold Coated Silica Nanospheres and Surface Enhanced Raman Spectroscopy

The principal goal is to create a durable, reproducible biosensor to detect organophosphates at low concentration levels. Organophosphate pesticides are less harmful to the environment; however they can be more toxic and even deadly to animals and humans since they are not specifically targeting insects. Creating a biosensor will be accomplished by using gold coated silica nanospheres layered and topped with acetylcholinesterase. Using Surface Enhanced Raman Spectroscopy, the inhibition of acetylcholinesterase should be detectable even with low levels of organophosphates.

Determination of Arson Accelerants by GC-MS using SPME Fibers

Gas Chromatography-Mass Spectroscopy (GC-MS) can be used to aid in arson investigations. Solid phase micro extraction (SPME) fibers have been found to detect very low concentrations of accelerants and have been proven to be a useful tool. We will investigate controlled burns and analyze the headspace by GC-MS and SPME fibers to develop a laboratory for upper level chemistry students. The objective of the laboratory will be to correctly identify the accelerant used to set a fire. We will use different accelerants and different burn materials, varying burn time, the time the burn vapors are left uncontained, and the exposure time of the fiber. Once the parameters have been optimized and we have determined a sufficient method, the upper level laboratory will be constructed to fit within the allotted three-hour lab session.

Development of an Analytical Chemistry Experiment Involving Surface Enhancement of Raman Spectroscopy using Silver Nanoparticles

Raman spectroscopy is a technique used to examine the vibrational and rotational frequencies in a system.  An important advantage of Raman spectroscopy for chemical analysis is, as opposed to IR, it is able to use water as a solvent.  A Raman spectrum is acquired by irradiating a sample with a laser source of visible or near-infrared monochromatic radiation.  When the sample is irradiated by the beam of energy, it causes the electrons to shift from the ground state to a virtual state.  Some electrons will return to a vibrational or rotational level within the ground state that is different from their original state.  This causes frequency of radiation to be released that is different from the excitation frequency.  The scattered radiation is measured using a sensitive spectrometer to acquire a spectrum.  In this experiment, the sample being exposed to the laser is diluted in aliquots until the Raman spectrum only displays a slight peak.  Then using silver nanoparticles obtained by citrate reduction, the spectrum will be enhanced.  This enhancement of the Raman spectra is known as Surface Enhanced Raman spectroscopy (SERS).    Silver nanoparticles are added to the sample and as a consequence, the sample is absorbed onto the surface.  Because of the roughened surfaces of the metal, the spectrum increases due to the resonance involved.  The resonance allows the excited electron to immediately relax into a vibrational level of the ground state forcing a strong narrow peak.  The experiment being developed allows student to take spectra of diluted solutions to see the effects of concentration and then to see the effects of adding silver nanoparticles to enhance the spectra.