Selective Detection of Non-Aromatic Pesticides via Cyclodextrin-Promoted Fluorescence Modulation

Reported herein is the detection of aliphatic pesticides using cyclodextrin-promoted fluorescence modulation. The introduction of the pesticide leads to noticeable changes in the emission of a fluorophore held in close proximity by cyclodextrin, leading to a pesticide detection system that operates with 100% successful differentiation and low limits of detection

Sweet, Sweet Science: Addressing the Gender Gap in STEM Disciplines through a One-Day High School Program in Sugar Chemistry

Reported herein is the design, implementation, and evaluation of a full-day outreach program for high school girls that focuses entirely on sugar-related activities. The program, which we ran in February 2016 and February 2017, included multiple hands-on sugar-based experiments to increase the participants’ interest in and enthusiasm for science. The success of the program was quantitatively evaluated through the administration of precamp and postcamp surveys. Overall, the survey results indicated a statistically significant improvement in responses in one of the two program years, which corresponds to success in changing the participants’ attitudes regarding the practical applicability of science and in increasing their interest in pursuing scientific careers

Detection of bacterial spores with lanthanide-macrocycle binary complexes

The detection of bacterial spores via dipicolinate-triggered lanthanide luminescence has been improved in terms of detection limit, stability, and susceptibility to interferents by use of lanthanide−macrocycle binary complexes. Specifically, we compared the effectiveness of Sm, Eu, Tb, and Dy complexes with the macrocycle 1,4,7,10-tetraazacyclododecane-1,7-diacetate (DO2A) to the corresponding lanthanide aquo ions. The Ln(DO2A)^+ binary complexes bind dipicolinic acid (DPA), a major constituent of bacterial spores, with greater affinity and demonstrate significant improvement in bacterial spore detection. Of the four luminescent lanthanides studied, the terbium complex exhibits the greatest dipicolinate binding affinity (100-fold greater than Tb^(3+) alone, and 10-fold greater than other Ln(DO2A)^+ complexes) and highest quantum yield. Moreover, the inclusion of DO2A extends the pH range over which Tb−DPA coordination is stable, reduces the interference of calcium ions nearly 5-fold, and mitigates phosphate interference 1000-fold compared to free terbium alone. In addition, detection of Bacillus atrophaeus bacterial spores was improved by the use of Tb(DO2A)^+, yielding a 3-fold increase in the signal-to-noise ratio over Tb^(3+). Out of the eight cases investigated, the Tb(DO2A)^+ binary complex is best for the detection of bacterial spores

Environmental Application of Cyclodextrin Metal-Organic Frameworks in an Undergraduate Teaching Laboratory

Reported herein is a multidisciplinary laboratory experiment for advanced undergraduate students that includes elements of material synthesis, in the synthesis of cyclodextrin-containing metal–organic frameworks (CD-MOFs), and environmental chemistry, in the use of these MOFs for pollutant removal. This multiday laboratory experiment starts with the synthesis of cyclodextrin-containing metal–organic frameworks (CD-MOFs) using vapor diffusion crystal growth procedures, followed by the use of the CD-MOFs for a pollutant removal application. Specifically, the CD-MOFs were used for the removal of a methylene blue dye (a common mimic of aromatic pollutants) from an organic solution, with the monitoring of the success of the removal procedures using UV–vis spectroscopy. This experiment was implemented as part of a larger multiday unit, and undergraduate students were particularly engaged with and excited by the CD-MOF synthesis and methylene blue removal experimental modules. As a result, the decision was made to make these two components a stand-alone multidisciplinary laboratory experiment, the results of which are reported herein

Efficient Detection of Phthalate Esters in Human Saliva via Fluorescence Spectroscopy

The detection of phthalates in human biologic fluids remains an important research objective because it provides an important measure of an individual’s exposure to this class of compounds, which have known deleterious health effects. Moreover, the ability to accomplish such detection in fluids that are easy to collect, such as saliva and urine, provides additional practical advantages. Reported herein is the application of cyclodextrin-promoted fluorescence energy transfer and fluorescence modulation to accomplish precisely such detection: the development of sensitive and selective florescence-based detection methods for phthalates in saliva, an easily collectable human biologic fluid. Such saliva-based detection methods occur with high levels of selectivity (100% differentiation) and sensitivity (limits of detection as low as 0.089 µM), and provide significant potential in the development of practical phthalate detection devices

Use of α-cyclodextrin to Promote Clean and Environmentally Friendly Disinfection of Phenolic Substrates via Chlorine Dioxide Treatment

The use of chlorine dioxide to disinfect drinking water and ameliorate toxic components of wastewater has significant advantages in terms of providing safe water. Nonetheless, significant drawbacks toward such usage remain. These drawbacks include the fact that toxic byproducts of the disinfection agents are often formed, and the complete removal of such agents can be challenging. Reported herein is one approach to solving this problem: the use of α-cyclodextrin to affect the product distribution in chlorine dioxide-mediated decomposition of organic pollutants. The presence of α-cyclodextrin leads to markedly more oxidation and less aromatic chlorination, in a manner that is highly dependent on analyte structure and other reaction conditions. Mechanistic hypotheses are advanced to explain the cyclodextrin effect, and the potential for use of α-cyclodextrin for practical wastewater treatment is also discussed

Fluorescence-Based Detection of Benzene, Toluene, Ethylbenzene, Xylene, and Cumene (BTEXC) Compounds in Fuel-Contaminated Snow Environments

Reported herein is the sensitive and selective cyclodextrin-promoted fluorescence detection of benzene, toluene, ethylbenzene, xylene, and cumene (BTEXC) fuel components in contaminated snow samples collected from several locations in the state of Rhode Island. This detection method uses cyclodextrin as a supramolecular scaffold to promote analyte-specific, proximity-induced fluorescence modulation of a high-quantum-yield fluorophore, which leads to unique fluorescence responses for each cyclodextrin-analyte-fluorophore combination investigated and enables unique pattern identifiers for each analyte using linear discriminant analysis (LDA). This detection method operates with high levels of sensitivity (sub-micromolar detection limits), selectivity (100% differentiation between structurally similar compounds, such as ortho-, meta-, and para-xylene isomers), and broad applicability (for different snow samples with varying chemical composition, pH, and electrical conductivity). The high selectivity, sensitivity, and broad applicability of this method indicate significant potential in the development of practical detection devices for aromatic toxicants in complex environments

Calcium Coordination Solids for pH-Triggered Release of Olsalazine

Calcium coordination solids were synthesized and evaluated for delivery of olsalazine (H_4olz), an anti-inflammatory compound used for treatment of ulcerative colitis. The materials include one-dimensional Ca(H_2olz)⋅4 H_2O chains, two-dimensional Ca(H_2olz)⋅2 H_2O sheets, and a three-dimensional metal-organic framework Ca(H_2olz)⋅2DMF (DMF=N,N-dimethylformamide). The framework undergoes structural changes in response to solvent, forming a dense Ca(H_2olz) phase when exposed to aqueous HCl. The compounds Ca(H_2olz)⋅x H_2O (x=0, 2, 4) were each pressed into pellets and exposed to simulated gastrointestinal fluids to mimic the passage of a pill from the acidic stomach to the pH-neutral intestines. All three calcium materials exhibited a delayed release of olsalazine relative to Na_2(H_2olz), the commercial formulation, illustrating how formulation of a drug within an extended coordination solid can serve to tune its solubility and performance