Ultrasensitive and versatile hydrogen peroxide sensing fluorescence quenching.

Reported herein is an ultra-sensitive turn-off fluorescence sensor for hydrogen peroxide based on its reaction with bimane 1. This reaction is highly efficient, resulting in a detection limit of 7.9 pM.

Shining light on fluoride detection: a comprehensive study exploring the potential of coumarin precursors as selective turn-on fluorescent chemosensors.

In this study, we report a fluoride chemosensor based on the use of a non-fluorescent pre-coumarin, compound 1. This compound undergoes selective fluoride-triggered formation of coumarin 2, with a concomitant turn-on fluorescence signal. Although compound 1 exists as a mixture of alkene isomers (2 : 1 in favor of the isomer), only the minor -isomer undergoes cyclization.

Paper-based manganese and β-cyclodextrin sensors for colorimetric sulfur dioxide detection.

Reported herein is a novel detection method for sulfur dioxide in aqueous solutions, in which the presence of sulfur dioxide leads to color changes of filter paper modified with both β-cyclodextrin and manganese. This detection method is rapid (less than 5 min required for complete color change), sensitive (limits of detection as low as 33 ppm), broadly applicable (tolerant of a range of pH values), and practical (color changes can be observed via naked eye detection and quantified via straightforward color analysis). Extensive optimization of each component provides insight into the unique stabilizing effect of cyclodextrin in preventing the filter paper from permanganate-induced degradation, and mechanistic analysis points to an oxidation-reduction reaction as responsible for the observed color changes.

Highly Sensitive Water Detection Through Reversible Fluorescence Changes in a -Bimane Based Boronic Acid Derivative.

Reported herein is a fluorometric and colorimetric sensor for the presence of trace amounts of water in organic solvents, using -bimane based boronate ester . This sensor responds to the presence of water with a highly sensitive turn-off fluorescence response, with detection limits as low as 0.018% water (v/v).

A dipodal bimane-ditriazole-diCu(II) complex serves as an ultrasensitive water sensor.

An ultrasensitive fluorescent water sensor based on a dipodal bimane-Cu(II) complex is reported here. This complex, which is non-fluorescent in the absence of water, demonstrates a remarkable turn-on fluorescence in the presence of extremely low (0.000786% v/v) concentrations of water, highly selective water-induced displacement of copper and restoration of the innate bimane fluorescence.

Sonication-Induced, Solvent-Selective Gelation of a 1,8-Napthalimide-Conjugated Amide: Structural Insights and Pollutant Removal Applications.

Reported herein is the synthesis, characterization, and dye removal applications of a highly solvent-selective organogel-forming amide, compound , which contains a 1,8-naphthalmide moiety, flexible -hexyl chain, and benzene ring. This compound displayed remarkable solvent selectivity, with gel formation occurring only in the presence of alkylated aromatic solvents. Detailed structural characterization of the gels, combined with notable theoretical insights, is invoked to explain the highly selective gelation properties of compound , as is a comparison to non-gel forming structural isomer , which contains the same structural elements in a different arrangement.

Ronald C.D. Breslow (1931-2017): A career in review.

Reviewed herein are key research accomplishments of Professor Ronald Charles D. Breslow (1931-2017) throughout his more than 60 year research career. These accomplishments span a wide range of topics, most notably physical organic chemistry, medicinal chemistry, and bioorganic chemistry.

Fluorescence-Based Sensing of Pesticides Using Supramolecular Chemistry.

The detection of pesticides in real-world environments is a high priority for a broad range of applications, including in areas of public health, environmental remediation, and agricultural sustainability. While many methods for pesticide detection currently exist, the use of supramolecular fluorescence-based methods has significant practical advantages. Herein, we will review the use of fluorescence-based pesticide detection methods, with a particular focus on supramolecular chemistry-based methods.

Highly sensitive detection of cobalt through fluorescence changes in β-cyclodextrin-bimane complexes.

A supramolecular complex of syn-(methyl,methyl)bimane (1) and β-cyclodextrin demonstrates a sensitive (limit of detection = 0.60 nM) and selective fluorescence turn-off response in the presence of cobalt in aqueous media, with calibration curves enabling quantitation in solution and using filter papers on which bimane and cyclodextrin were adsorbed. 1H NMR spectroscopy provides insight into interactions underlying the sensor performance.

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.

Efficient Detection and Removal of Polycyclic Aromatic Hydrocarbons Using Cyclodextrin-Modified Cellulose.

Covalent functionalization of cellulose with β-cyclodextrin by succinic acid-promoted cross-linking leads to a dual-function material that efficiently promotes proximity-induced energy transfer from polycyclic aromatic hydrocarbons (PAHs) to squaraine fluorophores with high quantum yields, and removes PAHs from aqueous solution through non-covalent binding. This material, which possesses a high functionalization density (0.17 μg/mm of cyclodextrin on cellulose), promotes energy transfer efficiencies as high as 58 % (for an anthracene donor in combination with a squaraine fluorophore acceptor), and leads to the removal of up to 91 % of a PAH (pyrene) from aqueous solution by mixing of the solution with the functionalized material.

Enhanced Characterization of Pyrene Binding in Mixed Cyclodextrin Systems via Fluorescence Spectroscopy.

Although significant effort has been expended to analyze the binding of pyrene in β-cyclodextrin and γ-cyclodextrin, little has been published on the binding of this guest in β-cyclodextrin derivatives (methyl-β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin) or in mixtures of such derivatives, despite the fact that these derivatives are known to have different supramolecular properties that facilitate unique modes of complexation. Reported herein is a detailed spectroscopic investigation of the binding of pyrene in β-cyclodextrin derivatives and in binary mixtures of cyclodextrins. Py values, defined as the ratio of representative vibronic bands in the fluorescence emission of pyrene, were used to measure changes in the pyrene microenvironment in the presence of the cyclodextrin hosts, and indicated that unmodified β-cyclodextrin is unique in providing a fully hydrophobic environment for pyrene through the use of two cyclodextrins to bind a single pyrene guest.

Detection of anabolic steroids cyclodextrin-promoted fluorescence modulation.

Reported herein is the detection of anabolic steroids through the use of cyclodextrin-promoted interactions between the analyte of interest and a high quantum yield fluorophore, which lead to measurable, analyte-specific changes in the fluorophore emission signal. By using a variety of β-cyclodextrin derivatives (unmodified β-cyclodextrin, methyl-β-cyclodextrin, and 2-hydroxypropyl-β-cyclodextrin) in combination with high quantum yield fluorophore rhodamine 6G, we detected five anabolic steroid analytes with 100% differentiation between structurally similar analytes and micromolar level limits of detection. Overall, these results show significant potential in the development of practical, fluorescence-based steroid detection devices.

A Paper-Based Device for Ultrasensitive, Colorimetric Phosphate Detection in Seawater.

High concentrations of certain nutrients, including phosphate, are known to lead to undesired algal growth and low dissolved oxygen levels, creating deadly conditions for organisms in marine ecosystems. The rapid and robust detection of these nutrients using a colorimetric, paper-based system that can be applied on-site is of high interest to individuals monitoring marine environments and others affected by marine ecosystem health. Several techniques for detecting phosphate have been reported previously, yet these techniques often suffer from high detection limits, reagent instability, and the need of the user to handle toxic reagents.

Ultrasensitive Detection of Nitrite through Implementation of -(1-Naphthyl)ethylenediamine-Grafted Cellulose into a Paper-Based Device.

Reported herein is the immobilization of -(1-naphthyl)ethylenediamine (NED) on cellulose via an epichlorohydrin (ECH)-based covalent attachment and the implementation of the functionalized cellulose into an ultrasensitive, paper-based device for nitrite detection. The reported functionalization procedure resulted in a 12.9-fold higher functionalization density than the density that results from the previously reported procedures, and the subsequent device allows for nitrite detection limits in synthetic freshwater and real seawater of 0.

Colorimetric Detection of Aliphatic Alcohols in β-Cyclodextrin Solutions.

The sensitive, selective, and practical detection of aliphatic alcohols is a continuing technical challenge with significant impact in public health research and environmental remediation efforts. Reported herein is the use of a β-cyclodextrin derivative to promote proximity-induced interactions between aliphatic alcohol analytes and a brightly colored organic dye, which resulted in highly analyte-specific color changes that enabled accurate alcohol identification. Linear discriminant analysis of the color changes enabled 100% differentiation of the colorimetric signals obtained from methanol, ethanol, and isopropanol in combination with BODIPY and Rhodamine dyes.

Identification of 15 Phthalate Esters in Commercial Cheese Powder via Cyclodextrin-Promoted Fluorescence Detection.

A challenge for detecting phthalates in commercial products such as cheese powders is that the composition of the products is highly complex, and current methods for detection rely on gas chromatography-mass spectrometry, which is not portable and cannot be used by individual consumers at a time and place of their choosing. Herein, we report the development of a new method for phthalate detection in cheese powder using cyclodextrin-promoted fluorescence detection, in which the presence of the phthalate analytes leads to highly analyte-specific changes in the fluorescence emission signal of a fluorophore bound in a cyclodextrin cavity. This method relies on subtle changes in the analyte affinity for the fluorophore and the cyclodextrin cavity and provides for markedly more straightforward sample preparation procedures and an extremely rapid read-out signal, with potential for the development of portable fluorescence sensors.

Effects of Structural Variation in Conjugated Side Chains on the Photophysics of Conjugated Polymers in Nanoparticles.

Conjugated polymers (CPs) are widely used for a variety of applications as a result of their high quantum yields, strong extinction coefficients, and good stability to a variety of experimental conditions. In many cases, the use of conjugated polymer nanoparticles (CPNs) provides additional practical advantages. The ability to understand how the structure of the CP affects its photophysical properties has the potential to significantly accelerate research in this area.

Supramolecular Luminescent Sensors.

There is great need for stand-alone luminescence-based chemosensors that exemplify selectivity, sensitivity, and applicability and that overcome the challenges that arise from complex, real-world media. Discussed herein are recent developments toward these goals in the field of supramolecular luminescent chemosensors, including macrocycles, polymers, and nanomaterials. Specific focus is placed on the development of new macrocycle hosts since 2010, coupled with considerations of the underlying principles of supramolecular chemistry as well as analytes of interest and common luminophores.

Cyclodextrin-Promoted Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Commercial Milk Products.

The detection of polycyclic aromatic hydrocarbons (PAHs) and their metabolites in food and in agricultural sources is an important research objective due to the PAHs' known persistence, carcinogenicity, and toxicity. PAHs have been found in the milk of lactating cows, and in the leaves and stems of plants grown in PAH-contaminated areas, thereby making their way into both cow milk and plant milk alternatives. Reported herein is the rapid, sensitive, and selective detection of 10 PAHs and PAH metabolites in a variety of cow milks and plant milk alternatives using fluorescence energy transfer from the PAH to a high quantum yield fluorophore, combined with subsequent array-based statistical analyses of the fluorescence emission signals.

Detection of Organochlorine Pesticides in Contaminated Marine Environments via Cyclodextrin-Promoted Fluorescence Modulation.

The development of practical and robust detection methods for pesticides is an important research objective owing to the known toxicity, carcinogenicity, and environmental persistence of these compounds. Pesticides have been found in bodies of water that are located near areas where pesticides are commonly used and easily spread to beaches, lakes, and rivers; affect the species living in those waterways; and harm humans who come into contact with or eat fish from such water. Reported herein is the rapid, sensitive, and selective detection of four organochlorine pesticides in a variety of water sources across the state of Rhode Island using cyclodextrin-promoted fluorescence detection.

Efficient Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Human Breast Milk.

Once chemical contaminants are released into the environment, there are a number of concerns that arise regarding the environmental persistence of the contaminants, their known and suspected toxicities, and their potential disruption to the ecosystem. One class of contaminants that is of continuing concern is polycyclic aromatic hydrocarbons (PAHs), persistent organic pollutants that are significant components of oil spills. PAHs have been found in the breast milk of nursing mothers living in oil spill affected regions, and can harm the nursing children.

Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions.

Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of -substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of -cyclohexylmaleimide with a methyl-β-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond.

Rapid and efficient pesticide detection via cyclodextrin-promoted energy transfer.

Cyclodextrins facilitate non-covalent fluorescence energy transfer from a variety of pesticides to high quantum-yield fluorophores, resulting in a rapid, sensitive detection scheme for these compounds with detection limits as low as two micromolar. Such a facile detection tool has significant potential applications in agriculture and public health research.