New Electrochemical and Optical Detection Methods for Biological and Environmental Applications

Detection of chromium and vanadium is of interest for biomedical and environmental applications. The two metals have narrow limits between being essential and toxic for humans. Ultra-sensitive techniques have been studied to measure Cr and V at low concentrations found in human blood and environmental samples. Bismuth film and mercury-alloy electrodes have been developed as alternatives to traditional Hg-based electrodes for Cr and V detection. While catalytic adsorptive stripping voltammetry (CAdSV) has been used to detect Cr and V, little is known about the process. The mechanisms of CAdSV have been probed to provide a better understanding of its exceptional sensitivity and selectivity. Near-real time monitoring of plume gas constituents is desired as a diagnostic tool for combustion efficiency, ensuring safe testing conditions and observing releases of green house gasses. Ground testing rockets is a crucial preliminary step that ensures their performance during critical space missions. Optical sol-gel sensors for carbon dioxide have been developed for remote sensing applications. They are inexpensive and are compatible with the harsh environments encountered during rocket plume tests. The sensors are a viable approach to compliment current infrared (IR) measurements for real-time carbon dioxide detection. Additional work on kerosene and isopropyl alcohol sensing has been explored for incorporation into a multi-analyte sensing platform

Cultivating a Community of STEM Polymaths at UNG

The University of North Georgia (UNG), Dahlonega, suffers from high attrition of STEM majors and low STEM graduation rates. In response to this challenge, a transdisciplinary (TD) team of UNG STEM faculty – from biology, chemistry, mathematics, and physics - has designed and developed hands-on laboratory experiments that employ empirical, interpretive, critical, and transdisciplinary research methodologies. The TD laboratory curriculum exposes undergraduate STEM students to cutting-edge techniques and new scientific frontiers, which will foster creativity and passion about scientific research, help undergraduates develop skills in analytical thinking and experimental design, and improve their technological fluency. In turn, this will improve persistence by stimulating student interest and participation in STEM. We will present examples of the transdisciplinary experiments that our students are engaging in and provide interactive activities to expose an interdisciplinary audience to the substantive scientific questions and real-world observations of the TD lab at UNG

A Transdisciplinary Laboratory Course Increases STEM Retention

STEM retention is a national challenge. Recent literature suggests that students leave STEM for many reasons including lack of context, lack of academic preparedness for entering college, and challenges with quantitative reasoning. These observations compelled us to design an introductory, transdisciplinary STEM lab course which we describe herein. This course was designed to integrate the disciplines of biology, chemistry, physics, and mathematics with activities that engage students in real-world, inquiry-based exercises and help students develop quantitative reasoning skills. Assessment showed that students in this STEM lab have higher STEM retention rates than those in equivalent disciplinary courses. The largest gains in STEM retention were seen in the 4th semester for students who took the lab as underclassmen. Additionally, student surveys indicated that students found the context of the lab compelling. In contrast, there were no significant differences in gains in quantitative literacy and reasoning or GPA among STEM lab students and students in discipline-specific labs. These results suggest that students’ engagement in applications of STEM with context might be more important for increasing retention than just focusing on academic ability alone

Magnetic Drug Delivery of Xanthohumol to Adipocytes Using Ultrasmall Superparamagnetic Iron Oxide Nanoparticles.

According to the CDC’s National Center for Health Statistics, more than one-third (36.5%) of U.S adults are obese. It is the main risk factor for type-2-diabetes, hypertension, dyslipidemia and atherosclerosis. Nutraceuticals such as Xanthohumol have shown potential to inhibit adipogeneis, however, their bioavailability has remained controversial. Hence there is a need to develop targeted therapy which will increase the concentration of Xanthohumol on adipose tissues. Currently, magnetic drug delivery has been used to develop targeted therapies where conventional therapies have proven to be less effective. Among various types of nanoparticles ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) have found considerable attention in magnetic drug delivery as they are easy to synthesize, inert, and are biocompatible. Hence to deliver Xanthohumol to adipose tissues we synthesized USPIO tagged Xanthohumol. The synthesized USPIO nanoparticles were amine functionalized using 3-aminotripropyl ethoxysilane. The presence of amine functional groups on the surface of USPIO was confirmed qualitatively using FTIR and quantitatively using ninhydrin Assay. The ninhydrin assay revealed that 1 mg of amine functionalized UPSIO had 22mg of amine groups. Xanthohumol was then conjugated to the surface of amine-USPIO using via a polyethylene glycol linker. The presence of Xanthohumol on the surface of nanoparticles was confirmed via FTIR. The amount of Xanthohumol tagged onto the surface of doped nanoparticles was quantified using HPLC. The particle size of the synthesized nanoparticles will be evaluated using TEM and the toxicity and therapeutic potency of Xanthohumol tagged to USPIO will be evaluated in vitro

1J: Chemically selective self-assembled monolayers for lowered limits of detection of Cr(VI)

Chromium most often exists in two natural oxidation states, Cr(III) necessary for life and Cr(VI) a carcinogen. Differentiating between the two states in public drinking water is crucial to determining whether or not that water is safe for public usage. In order to detect lower concentrations of the heavy metal and to distinguish between its two oxidation states, sensors employing pyridine self-assembled monolayers (SAMs) to a gold surface with Total Reflection X-Ray Fluorescence (TXRF) were proposed using a new protocol. It is hypothesized that these sensors will lower limits of detection and increase detection selectivity between Cr’s two common oxidation states. Electrochemical cycling of the gold surface prior to SAMs addition increased surface area to 2.40 * 10-14 µg/Å2, leading to an increase in the functional pyridine groups used to isolate Cr(VI). Data was confirmed by enhanced peak current from potassium ferrocyanide electrochemical cycling and quartz crystal microbalance (QCM) mass addition studies, with the increase in gold surface area allowing for 408.1% increase in Cr(VI) signal­. Future TXRF analysis can be applied to view the amplified signal of isolated Cr(VI), using the gold surface of the sensor as an internal standard. With electrochemical removal of Cr(VI) and use of the pyridine SAMs, these sensors are hypothesized to be reusable and chemically selective for Cr(VI) detection with improvement to limits of detection

Indirect Detection of Chromium using Monoliths and Sol-gels

The use of sol-gels as a chemical sensing matrix is attractive due to many of the unique physical and chemical properties they exhibit. In the current work, pyridine functionalized sol-gels were studied for their potential application in spectroelectrochemical sensing. Bulk sol-gel monoliths of varying formulations were tested to determine the optimal concentration of charge selective pyridine functional groups within the ion selective sensing sol-gel matrix. Process variables were investigated in order to produce uniform monoliths and material performance was tested by fluorescence spectroscopy. Once optimal formulations are determined, tests will be conducted on thin film electrodes which provide three modes of selectivity by means of chemically selective sol-gel films, electrochemical activity, and/or optical properties of the fluorescent redox probe, Ru(bpy)32 for the indirect simultaneous optical and electrochemical detection of Cr6+

Determination of Hop Alpha Acids and Hop Acid Utilization From Whirlpool Brewing Processes Using a Scaled-down Industrial Method and High Performance Liquid Chromatography

Hops are the female seed cones or flowers of the hop plant, humulus lupulus and contain chemical compounds, known as alpha (α) and beta (β) acids, which contribute to the bitterness, aroma, stability, and other final characteristics of beer. Nearly every commercial beer uses hops as the exclusive spice for flavoring. Three similar chemical varieties of α-acids (humulone, cohumulone, and adhumulone) are generally chemically rearranged when exposed to high temperatures during boiling to produce intensely bitter iso-α-acids. The β-acids (lupulone, colupulone, and adlupulone) and some unaltered α-acids are the main contributors to the aroma of the beer. Since hops are an important factor in the overall bitterness and aroma of beer, it is important to know the concentration of α-acids and the extent to which they will be chemically altered to the very bitter iso-α-acids (known as % utilization). There are a multitude of hops distributors worldwide (Hopunion, US organic hops, etc) that offer varieties of hops with various known concentrations of α-acids and β-acids. This information gives the brewer a very general understanding of the amount of hops to use, when to add the hops to the wort (unfermented beer), and the length of time the hops should be exposed to high temperatures to induce the chemical change to iso-α-acids. Commercial brewers are also recently applying a technique called whirlpooling to separate undesirable solids from the wort before fermenting the beer. For some styles of beer, copious amounts of hops are added to the whirlpool while the wort is still hot. This results in increased hop contact times with the heated wort (upwards of 60 min). It is generally assumed that hop utilization (% α-acids converted to iso-α-acids) from this technique is near zero, but this is highly unlikely and the brewing industry does not always have analytical quality control methods to make these determinations. To date, the only attempts to determine hop utilization from whilrpooling have been highly subjective, utilizing professional tasting panels rather than actual detection of α- and β- acids and iso-acids. The initial goal of this work is to use a characterization technique called High Performance Liquid Chromatography (HPLC) to quantify the hop acid content and determine how various whirlpool process factors will affect hop utilization

Stabilization of tetrameric metavanadate ion by tris(1,10-phenanthroline)cobalt(III) complex cation: Synthesis, spectroscopic and X-ray structural study of [Co(phen)3]3(V4O12)2Cl.27H2O

A new complex salt of composition [Co(phen)3]3(V 4O12)2Cl.27H2O (phen = 1,10-phenanthroline and [V4O12]4- = tetrameric metavanadate, dodecaoxotetravanadate ion) was synthesized by the reaction of appropriate salts in aqueous medium. The complex salt has been characterized by elemental analyses, thermogravimetric analysis, cyclic voltammetry, FT-IR, and UV-Vis spectroscopies, solubility product and conductance measurements. Single crystal X-ray structure determination revealed ionic structure consisting of three complex cations, [Co(phen)3]3+, two [V 4O12]4- anions, one chloride and 27 lattice water molecules. Detailed structural and spectroscopic analyses of [Co(phen)3]3(V4O12) 2Cl.27H2O showed that the large anion is stabilized by large cationic metal complex as there is preferred shape compatibility that leads to a large number of lattice-stabilizing non-covalent interactions

A reflection-mode fibre-optic sensor for breath carbon dioxide measurement in healthcare

A reflection-mode carbon dioxide (CO2) fibre optic sensor (FOS) is developed based on the colorimetric change of pH indicator dye thymol blue. The CO2 sensing film comprises thymol blue and tetramethylammonium hydroxide in the form of an ion pair doped in an organically modified silica film. A dip coating process was conducted to coat the sensing film on the tip of optical fibre with a film thickness approximately 2.7 ± 0.1 μm. The observed reflection signal at a wavelength of 608 nm exhibits a reversible change for the concentration of CO2 range from 0 to 6% with a response time of 19 s and recovery time of 170 s for 6% of CO2. An optimal concentration of thymol blue in the preparation of coating solution that provides a highest sensitivity was found to be 2.9 mg/ml. Storing the FOS in a pure nitrogen atmosphere provided a stable film with a shelf-life of over 15 days as compared to a gradual degradation in film performance and complete loss of sensitivity after 10 days with storage in ambient air. The FOS response is affected by relative humidity (RH) and a humidity filter was demonstrated to reduce humidity levels in breath from 90% to 40–50% to reduce this effect. The developed FOS was used to measure the end-tidal breath CO2 for testing its applicability in healthcare. The CO2 measurement from breath sample using our FOS shows a good agreement (percentage error~3%) with a commercial CO2 datalogger (K-33 BLG, CO2 Meter, USA). Due to the limitation of response time, at present the FOS is limited to measuring variation of the CO2 from slow breath to breath. Keywords: Optical fibre CO2 sensor, Colorimetric change, pH indicator, Thymol blue, Sol-gel, End-tidal CO