The therapeutic use of rose bengal (RB) has been limited by its anionic nature, high water solubility, and short half-life. Herein, RB was converted into a group of uniform materials based on organic salts (GUMBOS) via ion metathesis reactions to replace its sodium counterions with distinct cationic antiseptics (i.e., benzyldimethylhexadecylammonium, BZK; cetylpyridinium, C16Py; and chlorhexidine, CHX). The potential use of RB-based GUMBOS as antibacterial agents was investigated against a panel of Gram-positive and Gram-negative bacteria, namely Staphylococcus aureus (S. aureus), methicillin-resistant S. aureus (MRSA), Enterococcus faecalis (E. faecalis), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli). The micro-broth dilution method was used to determine the minimum inhibitory concentration (MIC) of synthesized GUMBOS as well as their parent compounds and unreacted stoichiometric mixtures. Hemolytic effects were further studied using human red blood cells. When compared to parent compounds and unreacted mixtures, GUMBOS showed equal or improved activity towards the non-resistant strain of S. aureus (i.e., DSM 2569) and E. faecalis. Additionally, [CHX][RB] was found to be active against E. coli with a MIC of 6.4–0.8 nmol mL−1, being 79 and 48 times more potent than RB and the corresponding unreacted mixture. The [CHX][RB] GUMBOS also showed the lowest hemolytic activity among all tested compounds and mixtures (percentage of hemolysis <5%). Overall, these results demonstrated that this ion metathesis strategy can improve the antibacterial activity of RB against Gram-positive bacteria and extend its spectrum of action towards E. coli, which could further contribute to safety improvements in multiple industries.

Tuning the 8-anilino-1-naphthalenesulfonic acid (ANS) structure usually requires harsh conditions and long reaction times, which can result in low yields. Herein, ANS was modified to form an ANS group of uniform materials based on organic salts (GUMBOS), prepared with simple metathesis reactions and distinct cations, namely tetrabutylammonium (N4444), tetrahexylammonium (N6666), and tetrabutylphosphonium (P4444). These ANS-based GUMBOS were investigated as fluorescent probes for membrane binding studies with four proteins having distinct physicochemical properties. Liposomes of 1,2-dimyristoyl- sn-glycero-3-phosphocholine were employed as membrane models as a result of their ability to mimic the structure and chemical composition of cell membranes. Changes in fluorescence intensity were used to monitor protein binding to liposomes, and adsorption data were fitted to a Freundlich-like isotherm. It was determined that [N4444][ANS] and [P4444][ANS] GUMBOS have enhanced optical properties and lipophilicity as compared to parent ANS. As a result, these two GUMBOS were selected for subsequent protein-membrane binding studies. Both [N4444][ANS] and [P4444][ANS] GUMBOS and parent ANS independently reached membrane saturation within the same concentration range. Furthermore, distinct fluorescence responses were observed upon the addition of proteins to each probe, which demonstrates the impact of properties such as lipophilicity on the binding process. The relative maintenance of binding cooperativity and maximum fluorescence intensity suggests that proteins compete with ANS-based probes for the same membrane binding sites. Finally, this GUMBOS-based approach is simple, rapid, and involves relatively small amounts of reagents, making it attractive for high-throughput purposes. These results presented herein can also provide relevant information for designing GUMBOS with ameliorated properties.

Herein, hydrophobic coating materials are reported for QCM detection of VOCs under dry and humid conditions. In this study, IR780-based GUMBOS ([IR780][OTf] and [IR780][NTf2]) were synthesized using an ion exchange reaction and the anions trifluoromethanesulfonimide ([OTf]) and bisperfluoromethanesulfonimide ([NTf2]). The parent iodide salts and GUMBOS ([IR780][I]), [IR780][OTf], and [IR780][NTf2]) were characterized using several analytical techniques. These salts were then employed as sensor coatings on quartz crystal resonators using an electrospray coating method. These sensors were exposed to four flow ratios of five common VOCs in the absence and presence of 10 vol% water. Fundamental frequency responses were recorded and further employed as input variables to develop highly accurate multi-sensor arrays (MSAs). Accuracy was more than 78.3% without water, and more than 91.7% in the presence of water. When multi-harmonic responses were evaluated as input variables to assess discrimination ability for each sensor, highly accurate virtual sensor arrays (VSAs) were able to be developed for each GUMBOS coating. In the case of [IR780][NTf2], a slight improvement in discrimination was achieved in the presence of water (95%) versus the absence of water. Moreover, this study highlights development of readily synthesized hydrophobic coatings of IR780-based GUMBOS for potential detection and discrimination of VOCs in aqueous systems.

Antimicrobial resistance is a silent pandemic considered a public health concern worldwide. Strategic therapies are needed to replace antibacterials that are now ineffective. One approach entails the use of well-known antibacterials along with adjuvants that possess non-antibiotic properties but can extend the lifespan and enhance the effectiveness of the treatment, while also improving the suppression of resistance. In this regard, a group of uniform materials based on organic salts (GUMBOS) presents an alternative to this problem allowing the combination of antibacterials with adjuvants. Fluoroquinolones are a family of antibacterials used to treat respiratory and urinary tract infections with broad-spectrum activity. Ciprofloxacin and moxifloxacin-based GUMBOS were synthesized via anion exchange reactions with lithium and sodium salts. Structural characterization, thermal stability and octanol/water partition ratios were evaluated. The antibacterial profiles of most GUMBOS were comparable to their cationic counterparts when tested against Gram-positive S. aureus and Gram-negative E. coli, except for deoxycholate anion, which demonstrated the least effective antibacterial activity. Additionally, some GUMBOS were less cytotoxic to L929 fibroblast cells and non-hemolytic to red blood cells. Therefore, these agents exhibit promise as an alternative approach to combining drugs for treating infections caused by resistant bacteria.

Herein, hydrophobic coating materials are reported for QCM detection of VOCs under dry and humid conditions. In this study, IR780-based GUMBOS ([IR780][OTf] and [IR780][NTf2]) were synthesized using an ion exchange reaction and the anions trifluoromethanesulfonimide ([OTf]) and bisperfluoromethanesulfonimide ([NTf2]). The parent iodide salts and GUMBOS ([IR780][I]), [IR780][OTf], and [IR780][NTf2]) were characterized using several analytical techniques. These salts were then employed as sensor coatings on quartz crystal resonators using an electrospray coating method. These sensors were exposed to four flow ratios of five common VOCs in the absence and presence of 10 vol% water. Fundamental frequency responses were recorded and further employed as input variables to develop highly accurate multi-sensor arrays (MSAs). Accuracy was better than 78.3% without water, and better than 91.7% in the presence of water. When multi-harmonic responses were evaluated as input variables to assess discrimination ability for each sensor, highly accurate virtual sensor arrays (VSAs) were developed using each GUMBOS coating. In the case of [IR780][NTf2], a slight improvement in discrimination was achieved in the presence of water (95%) versus the absence of water. Moreover, this study highlights development of readily synthesized hydrophobic coatings of IR780-based GUMBOS for potential detection and discrimination of VOCs in aqueous systems.

Although institutions of higher education have placed a large emphasis on increasing the number of underrepresented minority (URM) students matriculating in higher education, the disparities in STEM retention and graduation rates between URM and non-URM students emphasize the dire need for increased support to help URM students navigate challenges including stereotype threat, impostor phenomenon, and lack of social connectedness that disproportionately affect URM students in majority-dominated fields. Prior research has demonstrated that structured mentoring has the potential to generate substantial improvements in academic, social, and career outcomes for URM STEM students. In particular, network-based mentoring approaches that allow for students to receive both professional and peer mentoring, as well as the opportunity to mentor other students, have demonstrated success in this realm. In this article, we discuss how the current state of academia often fails URM STEM students and faculty, review literature regarding the ways in which structured mentoring approaches can alleviate barriers to success among URM groups in STEM fields, and offer recommendations regarding how academic institutions can successfully implement holistic student and faculty mentoring programs.

Here we report a thermoset shape memory polymer-based syntactic foam inherently integrated with flame retardancy, good mechanical properties, excellent shape memory effect, and 3D printability. The syntactic foam is fabricated by incorporating a high-temperature shape memory polymer (HTSMP) as the matrix, with 40 vol % hollow glass microspheres (HGM) K20, K15, and K1 as fillers. Compressive behavior, strain-controlled programming followed by free recovery, stress recovery, and flame retardancy of these three syntactic foams were studied. Dynamic mechanical analysis and thermal characterization validate their high glass transition temperature (T g = ∼250 °C) and excellent thermal stability. Our results suggest that the foam consisting of K20 HGM exhibits high compressive strength (81.8 MPa), high recovery stress (6.8 MPa), and excellent flame retardancy. Furthermore, this syntactic foam was used for three-dimensional (3D) printing by an extruder developed in our lab. Honeycomb, sinusoidal shapes, and free-standing helical spring were printed for demonstration. This high-temperature photopolymer-based syntactic foam integrated with high T g, flame retardancy, high recovery stress, and 3D printability can be beneficial in different sectors such as aerospace, construction, oil and gas, automotive, and electronic industries.

GUMBOS (Group of Uniform Materials Based on Organic Salts) have recently emerged as interesting materials for protein analysis due to their unique features and high tunability. In this regard, four novel erythrosin B (EB)based GUMBOS were synthesized and their potential to discriminate among proteins with distinct properties (e. g., size, charge, and hydrophobicity) was assessed. These solid-phase materials were prepared using a single-step metathesis reaction between EB and various phosphonium and ammonium cations, namely tetrabutylphosphonium (P4444+), tributylhexadecylphosphonium (P44416+), tetrabutylammonium (N4444+), and benzyldimethylhexadecylammonium (BDHA+). Subsequently, the effect of pH (3.0, 4.5, and 6.0) and reaction time (5, 10, and 15 min) on the discriminatory power of synthesized GUMBOS was evaluated. Absorption spectra resulting from the interaction between EB-based GUMBOS and proteins were analyzed using partial least squares discriminant analysis (PLSDA). Unlike time, the pH value was determined to have influence over GUMBOS discrimination potential. Correct protein assignments varied from 86.5% to 100.0%, and the best discriminatory results were observed for [P4444]2[EB] and [N4444]2[EB] at pH 6.0. Additionally, these two GUMBOS allowed discrimination of protein mixtures containing different ratios of albumin and myoglobin, which appeared as individualized clusters in the PLSDA scores plots. Overall, this study showcases EB-based GUMBOS as simple synthetic targets to provide a label-free, cost-effective, rapid, and successful approach for discrimination of single proteins and their mixtures.

Nanoparticles derived from a group of uniform materials based on organic salts (nanoGUMBOS) are considered promising candidates for protein analysis due to their facile synthesis in aqueous media and high tunability. In this study, a phosphonium-erythrosin B-based nanoGUMBOS (i.e., [P4444]2[EB]) was prepared using an ultrasound-assisted reprecipitation method, and its ability to discriminate and quantify proteins was evaluated. Sonication time (30 s, 5 min, and 15 min) and cyclodextrin templating (alpha-, 2-HP-beta-, and gamma-CD) were investigated for their effects on discrimination performance of synthesized nanomaterial. Six proteins (albumin, hemoglobin, trypsin, catalase, lysozyme, and cytochrome c) with different abundance levels and physicochemical properties were selected as target analytes. Absorbance response patterns generated from interactions between [P4444]2[EB] nanoGUMBOS and proteins were analyzed using partial least squares discriminant analysis. Percentages of correct protein discrimination ranged from 94.6 to 99.6%, with the latter being the best result obtained using non-templated nanoGUMBOS formed after 5 min sonication. Under optimized conditions, it was possible to discriminate all protein samples with percentages of correct assignments greater than 90% for concentrations as low as 2.0 mu g mL-1. The discrimination capability of synthesized nanoGUMBOS was further evaluated using mixtures of different ratios of lysozyme, cytochrome c, and hemoglobin. Finally, partial least squares models were developed for protein quantification and the best performance was observed for albumin. Results support potential use of [P4444]2[EB] nanoGUMBOS in combination with ultraviolet-visible spectroscopy and chemo-metrics for qualitative and quantitative analyses of individual proteins and mixtures of proteins.

Three African American analytical chemists, whose primary research careers have focused in the respective sectors of academia, government, and industry, have come together to provide personal perspectives on parameters that have impacted their careers as well as to provide their perceptions of the current and future status of African Americans in the overall science, technology, engineering, and mathematics (STEM) enterprise, and the more specific field of analytical chemistry. The authors, having ∼150 years of combined experiences, reflect on the past status and contemplate future advances for African Americans in STEM. The most important factors during their formative years that underpinned their success over the long-term are enumerated. Particularly cited are the distinct features within the Historically Black Colleges and Universities (HBCU) environment that placed them solidly on a path toward successful careers. The Grand Challenge now and for the foreseeable future, reversal of the dysfunctional metropolitan public-school systems, is cited and the only perceived light in the tunnel for addressing this issue is mentioned. Finally, recommendations are made for the future where diversity within the STEM enterprise will be a prerequisite for U.S. competitiveness in our global society.

The quartz crystal microbalance (QCM) has been widely used in laboratory settings as an analytical tool for recognizing and discriminating biological and chemical molecules of interest. As a result, recent studies have shown there to be considerable attention in practical applications of the QCM technique beyond the laboratory. However, most commercial QCM instruments are not suitable for off-laboratory usage. For field-deployable applications and in situ detection, the development of a portable QCM measurement system achieving comparable performance to benchtop instruments is highly desired. In this paper, we describe the development of a fully customizable, miniaturized, battery-powered, and cost-efficient QCM system employing a phase-locked loop (PLL) electronic circuit-based QCM measurement system. The performance of this developed system showed a minimum frequency resolution of approximately 0.22 Hz at 0.1 s measurement time. This novel, miniaturized system successfully demonstrated an ability to detect two common volatile organic compounds (VOCs), methanol and dichloromethane (DCM), and the obtained results were comparable to responses from a commercially available benchtop instrument.

In recent years, advanced materials with properties resembling biological systems, particularly artificial muscles, have received intense scrutiny. This is because the interesting conformational shape characteristics of such materials have benefited a variety of technologies, including textiles, 3D printing, and medical devices. Although a multitude of shape memory properties have been studied and developed in recent years, self-healing of these polymers after puncture or rupture has also become a major area of study. Most techniques for detection of such processes are mechanically based and require considerable hands-on monitoring. Thus, a rapid visual detection method for self-healing is highly desirable. Herein, we describe fluorescence studies for rapid detection of self-healing properties of a partially neutralized sodium ionomer poly(ethylene-co-methacrylic acid) (PEMA). In this study, two different fluorophores, parent non-ionic 4,6-dipyrenylpyrimidine and ionic 4,6-dipyrenylpyrimidinium iodide fluorophores, were evaluated as possible sensors of self-healing. Incorporation of these probes via solution blending and compatibility into a PEMA of these fluorophores were evaluated. Thermal characterizations using differential scanning calorimetry were also performed to elucidate physical characteristics of healed sites. Ratiometric fluorescence emission variations were explored within puncture-healed ionomer films and related to Young's modulus properties with good linearity, indicating potential utility of this approach for monitoring elastic modulus properties after healing has occurred. Further statistical analyses of mechanical processes using quadratic discriminant analysis resulted in development of several highly accurate predictive models for determining time since damage healing.

In this study, three magnetic ionic liquids (MILs) were investigated for extraction of four estrogens, i.e., estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2), from environmental water. The cation trihexyl(tetradecyl)phosphonium ([P66614]+), selected to confer hydrophobicity to the resulting MIL, was combined with tetrachloroferrate(III), ferricyanide, and dysprosium thiocyanate to yield ([P66614][FeCl4]), ([P66614]3[Fe(CN)6]), and ([P66614]5[Dy(SCN)8]), respectively. After evaluation of various strategies to develop a liquid–liquid microextraction technique based on synthesized MILs, we placed the MILs onto a magnetic stir bar and used them as extracting solvents. After extraction, the MIL-enriched phase was dissolved in methanol and injected into an HPLC–UV for qualitative and quantitative analysis. An experimental design was used to simultaneously evaluate the effect of select variables and optimization of extraction conditions to maximize the recovery of the analytes. Under optimum conditions, limits of detection were in the range of 0.2 (for E3 and E2) and 0.5 μg L−1 (for E1), and calibration curves exhibited linearity in the range of 1–1000 μg L−1 with correlation coefficients higher than 0.998. The percent relative standard deviation (RSD) was below 5.0%. Finally, this method was used to determine concentration of estrogens in real lake and sewage water samples.

Ionic liquids (ILs) are defined as organic salts with melting points below 100 °C. Such ionic compounds are typically formed using bulky cations and/or bulky anions in order to produce liquids or lower melting solids. ILs have been widely explored in several research areas including catalysis, remediation, solvents, separations, and many others. The utility of such compounds has also been recently broadened to include solid phase ionic materials. Thus, researchers have pushed the boundaries of ILs chemistry toward the solid state and have hypothesized that valuable properties of ILs can be preserved and fine-tuned to achieve comparable properties in the solid state. In addition, as with ILs, tunability of these solid-phase materials can be achieved through simple counterion metathesis reactions. These solid-state forms of ILs have been designated as a group of uniform materials based on organic salts (GUMBOS). In contrast to ILs, these materials have an expanded melting point range of 25 to 250 °C. In this chapter, we focus on recent developments and studies from the literature that provide for fine tuning and enhancing properties through transformation and recycling of diverse ionic compounds such as dyes, antibiotics, and others into solid state ionic materials of greater utility.

Three novel small organic heterocyclic compounds: 2-(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound A), 1,3-di(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound B), and 1,3,6,8-tetra(1,2-diphenyl)-1H-benzimidazolepyrene (compound C) were synthesized and characterized for possible applications as blue OLED emitters. The specific molecular design targeted decreasing intermolecular aggregation and disrupting crystallinity in the solid-state, in order to reduce dye aggregation, and thus obtain efficient pure blue photo- and electroluminescence. Accordingly, the new compounds displayed reasonably high spectral purity in both solution- and solid-states with average CIE coordinates of (0.160 ± 0.005, 0.029 ± 0.009) in solution and (0.152 ± 0.007, 0.126 ± 0.005) in solid-state. These compounds showed a systematic decrease in degree of crystallinity and intermolecular aggregation due to increasing steric hindrance, as revealed using powder X-ray diffraction analysis and spectroscopic studies. An organic light-emitting diode (OLED) prototype fabricated using compound B as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m−2 at 5.5 V with an essentially pure blue electroluminescence corresponding to CIE coordinates of (0.1482, 0.1300). The highest EQE observed from this OLED prototype was 4.3 (±0.3)% at 3.5 V, and the highest luminance of 290 (±10) cd m−2 at 7.5 V. These values were found comparable to characteristics of the best pure blue OLED devices based on simple fluorescent small-molecule organic chromophores.

Herein, a solvent-based green recycling procedure is reported for recycling thermoset epoxy resins (TERs) and carbon fiber reinforced epoxy composites (CFRECs) employing ionic liquids (ILs) and alcohols under mild conditions. With melting points less than 100 °C, ILs are defined as organic salts, typically composed of bulky cations with organic or inorganic counteranions. As a result of their unique physical properties such as low vapor pressure, relatively high thermal stability, and multifunctional tunability, these solvents are often classified as "green solvents" as compared to traditional organic solvents. In this study, swelling and dissolution of TER are evaluated in the presence of pure alkyl-methyl-imidazolium ILs, alcohols, and various mixtures of these co-solvents to determine their swelling and depolymerization capacity at mild temperatures in the absence of catalysts. In these studies, three ILs with different alkyl lengths were evaluated: 1-butyl-3-methyl imidazolium chloride ([BMIm][Cl]), 1-hexyl-3-methyl imidazolium bromide ([HMIm][Br]), and 1-octyl-3-methyl imidazolium bromide ([OMIm][Br]) along with two alcohols: ethylene glycol (EG) and glycerol (Gly). The highest swelling capacity of TER at 150 °C was achieved by a combination of [BMIm][Cl] and EG. In addition, swelling and dissolution of TER were evaluated in the presence of several anion variants of 1-butyl-3-methyl-imidazolium ILs with EG. Complete dissolution of both TERs and CFRECs was achieved in 150 min (2.5 h) at 150 °C under atmospheric pressure. Finally, recovery and reuse of the recycled monomer after dissolution were examined. Recovered epoxy monomers employed to synthesize a recycled TER exhibited similar mechanical properties to the parent TER. In addition, it was demonstrated that carbon fibers could be successfully recovered from CFREC using the recycling method detailed in this manuscript.

Herein, an inexpensive commercially available sensor is presented for the detection of 4-nitrophenol (4NP) pollutant. Sodium fluorescein (NaFl) is used as a sensor to detect trace amounts of 4NP in acetonitrile (MeCN). The photophysical properties of NaFl were studied in two different solvents, MeCN (aprotic) and water (protic), with varying concentrations of different nitroaromatics using UV-visible absorption and fluorescence spectrophotometry. In an aqueous medium, photophysical properties of NaFl did not change in the presence of nitroaromatics. However, examination of the photodynamics in MeCN demonstrated that NaFl is extremely sensitive to 4NP (limit of detection: 0.29 µg/mL). This extreme specificity of NaFl towards 4NP when dissolved in MeCN, as compared to other nitroaromatics, is attributed to hydrogen bonding of 4NP with NaFl in the absence of water, resulting in both static and dynamic quenching processes. Thus, NaFl is demonstrated as a simple, inexpensive, sensitive, and robust optical turn off sensor for 4NP.

Volatile organic compounds (VOCs) that evaporate under standard atmospheric conditions are of growing concern. This is because it is well established that VOCs represent major contamination risks since release of these compounds into the atmosphere can contribute to global warming, and thus, can also be detrimental to the overall health of worldwide populations including plants, animals, and humans. Consequently, the detection, discrimination, and quantification of VOCs have become highly relevant areas of research over the past few decades. One method that has been and continues to be creatively developed for analyses of VOCs is the Quartz Crystal Microbalance (QCM). In this review, we summarize and analyze applications of QCM devices for the development of sensor arrays aimed at the detection of environmentally relevant VOCs. Herein, we also summarize applications of a variety of coatings, e.g., polymers, macrocycles, and ionic liquids that have been used and reported in the literature for surface modification in order to enhance sensing and selective detection of VOCs using quartz crystal resonators (QCRs) and thus QCM. In this review, we also summarize novel electronic systems that have been developed for improved QCM measurements.

Synthesis, characterization, and ultrafast dynamics of porphyrin- and zinc porphyrin-based nanomaterials are reported. Spherical nanoparticles composed of a group of uniform materials based on organic salts (nanoGUMBOS) are prepared from either porphyrin or zinc porphyrin with trihexyl(tetradecyl)phosphonium in aqueous colloidal suspension with sizes of approximately 50 nm in diameter. Ultrafast excited-state dynamics of porphyrin and zinc porphyrin nanoGUMBOS in water are measured using transient absorption spectroscopy with 400 nm excitation. Results are compared to corresponding measurements of the porphyrin molecular dye parent compounds in water. Porphyrin and zinc porphyrin have long-lived excited states arising from intersystem crossing of the first-excited singlet S-1 state to the triplet T-1 state. These excited-state lifetimes are significantly faster in porphyrin-based nanoGUMBOS as compared to the corresponding porphyrin molecules due to intermolecular energy transfer, electronic delocalization, and altered chemical environments of the nanomaterials. Additionally, these results demonstrate that porphyrin-based nanoGUMBOS are promising nanomaterials for light harvesting in solar cells and optoelectronics.