Sherine O. Obare

Nanoparticles Functionalized with Ampicillin Destroy Multiple-Antibiotic-Resistant Isolates of Pseudomonas aeruginosa and Enterobacter aerogenes and Methicillin-Resistant Staphylococcus aureus

ABSTRACT We show here that silver nanoparticles (AgNP) were intrinsically antibacterial, whereas gold nanoparticles (AuNP) were antimicrobial only when ampicillin was bound to their surfaces. Both AuNP and AgNP functionalized with ampicillin were effective broad-spectrum bactericides against Gram-negative and Gram-positive bacteria. Most importantly, when AuNP and AgNP were functionalized with ampicillin they became potent bactericidal agents with unique properties that subverted antibiotic resistance mechanisms of multiple-drug-resistant bacteria.

Size-dependent antimicrobial effects of novel palladium nanoparticles.

Investigating the interactions between nanoscale materials and microorganisms is crucial to provide a comprehensive, proactive understanding of nanomaterial toxicity and explore the potential for novel applications. It is well known that nanomaterial behavior is governed by the size and composition of the particles, though the effects of small differences in size toward biological cells have not been well investigated. Palladium nanoparticles (Pd NPs) have gained significant interest as catalysts for important carbon-carbon and carbon-heteroatom reactions and are increasingly used in the chemical industry, however, few other applications of Pd NPs have been investigated. In the present study, we examined the antimicrobial capacity of Pd NPs, which provides both an indication of their usefulness as target antimicrobial compounds, as well as their potency as potential environmental pollutants. We synthesized Pd NPs of three different well-constrained sizes, 2.0±0.1 nm, 2.5±0.2 nm and 3.1±0.2 nm. We examined the inhibitory effects of the Pd NPs and Pd2+ ions toward gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus) bacterial cultures throughout a 24 hour period. Inhibitory growth effects of six concentrations of Pd NPs and Pd2+ ions (2.5×10−4, 10−5, 10−6, 10−7, 10−8, and 10−9 M) were examined. Our results indicate that Pd NPs are generally much more inhibitory toward S. aureus than toward E. coli, though all sizes are toxic at ≥10−5 M to both organisms. We observed a significant difference in size-dependence of antimicrobial activity, which differed based on the microorganism tested. Our work shows that Pd NPs are highly antimicrobial, and that fine-scale (<1 nm) differences in size can alter antimicrobial activity.

Fluorescent Chemosensors for Toxic Organophosphorus Pesticides: A Review

Many organophosphorus (OP) based compounds are highly toxic and powerful inhibitors of cholinesterases that generate serious environmental and human health concerns. Organothiophosphates with a thiophosphoryl (P=S) functional group constitute a broad class of these widely used pesticides. They are related to the more reactive phosphoryl (P=O) organophosphates, which include very lethal nerve agents and chemical warfare agents, such as, VX, Soman and Sarin. Unfortunately, widespread and frequent commercial use of OP-based compounds in agricultural lands has resulted in their presence as residues in crops, livestock, and poultry products and also led to their migration into aquifers. Thus, the design of new sensors with improved analyte selectivity and sensitivity is of paramount importance in this area. Herein, we review recent advances in the development of fluorescent chemosensors for toxic OP pesticides and related compounds. We also discuss challenges and progress towards the design of future chemosensors with dual modes for signal transduction.

Nanostructured materials for environmental remediation of organic contaminants in water

Abstract Nanostructured materials have opened new avenues in various scientific fields and are providing novel opportunities in environmental science. The increased surface area-to-volume ratio of nanoparticles, quantum size effects, and the ability to tune surface properties through molecular modification make nanostructures ideal for many environmental remediation applications. We describe herein the fabrication of metal and semiconductor nanoparticles for environmental remediation applications, particularly in ground water. We then summarize literature reports of nanostructures specifically tailored for remediation of environmental contaminants including organohalides, trinitrotoluene, and phenols.

Selective blue emission from an HPBO-Li+ complex in alkaline media

2-(2-Hydroxyphenyl)benzoxazole (HPBO) exhibits enhanced fluorescence and specificity for Li+ compared to Na+ and K+, in an alkaline medium. The selectivity was observed in several organic solvents in the presence of bases such as pyridine, triethylamine and trimethylamine. HPBO–Li+ complex formation results in an intense blue emission readily observed by the naked eye under UV light. Spectroscopic titrations suggest that the structure of the complex is one in which two HPBO anionic ligands coordinate to one Li+, with a second Li+ as a counterion.

In situ immobilization of palladium nanoparticles in microfluidic reactors and assessment of their catalytic activity.

We report on the synthesis and characterization of catalytic palladium nanoparticles (Pd NPs) and their immobilization in microfluidic reactors fabricated from polydimethylsiloxane (PDMS). The Pd NPs were stabilized with D-biotin or 3-aminopropyltrimethoxysilane (APTMS) to promote immobilization inside the microfluidic reactors. The NPs were homogeneous with narrow size distributions between 2 and 4 nm, and were characterized by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and x-ray diffraction (XRD). Biotinylated Pd NPs were immobilized on APTMS-modified PDMS and glass surfaces through the formation of covalent amide bonds between activated biotin and surface amino groups. By contrast, APTMS-stabilized Pd NPs were immobilized directly onto PDMS and glass surfaces rich in hydroxyl groups. Fourier transform infrared spectroscopy (FT-IR) and x-ray photoelectron spectroscopy (XPS) results showed successful attachment of both types of Pd NPs on glass and PDMS surfaces. Both types of Pd NPs were then immobilized in situ in sealed PDMS microfluidic reactors after similar surface modification. The effectiveness of immobilization in the microfluidic reactors was evaluated by hydrogenation of 6-bromo-1-hexene at room temperature and one atmosphere of hydrogen pressure. An average first-run conversion of 85% and selectivity of 100% were achieved in approximately 18 min of reaction time. Control experiments showed that no hydrogenation occurred in the absence of the nanocatalysts. This system has the potential to provide a reliable tool for efficient and high throughput evaluation of catalytic NPs, along with assessment of intrinsic kinetics.

Editorial: core-shell nanostructures: modeling, fabrication, properties, and applications

1 School of Materials Science and Engineering, Central South University, Changsha, Hunan 410083, China 2 School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei, Anhui 230009, China 3College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, China 4Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of the Ministry of Education, Department of Physics, Hunan Normal University, Hunan Changsha 410081, China 5Materials Research Centre, Indian Institute of Science, Bangalore 560012, India 6Department of Chemistry, Western Michigan University, Kalamazoo, MI 49008, USA

Effects of surface activation on the structural and catalytic properties of ruthenium nanoparticles supported on mesoporous silica

Using colloid-based methods to prepare supported catalytic metallic nanoparticles (NPs) often faces the challenge of removing the stabilizer used during synthesis and activating the catalyst without modifying the particles or the support. We explored three surface activation protocols (thermal oxidation at 150 °C, thermal reduction at 350 °C, and argon-protected calcination at 650 °C) to activate ruthenium NPs supported on mesoporous silica (MSU-F), and assessed their effects on the structural and catalytic properties of the catalysts, and their activity by the aqueous phase hydrogenation of pyruvic acid. The NPs were synthesized by polyol reduction using poly-N-vinyl-2-pyrrolidone (PVP) as a stabilizer, and supported on MSU-F by sonication-assisted deposition. The NPs maintained their original morphology on the support during activation. Ar-protected calcination was the most efficient of the three for completely removing PVP from particle surfaces, and provided the highest degree of particle crystallinity and a metal dispersion comparable to commercial Ru/SiO2. Its catalytic performance was significantly higher than the other two protocols, although all three thermally activated catalysts achieved higher activity than the commercial catalyst at the same Ru loading. Post-reaction analysis also showed that the supported catalyst activated at 650 °C retained its morphology during the reaction, which is an important requirement for recyclability.

CHAPTER 5:The Green Synthesis and Environmental Applications of Nanomaterials

This chapter summarizes the use of green chemistry on the synthesis of nanomaterials as well as their environmental applications. Green routes for the synthesis of nanomaterials are discussed, including those using nontoxic solvents and natural template materials, such as ionic liquid, leaf and tea extract, natural cellulose, sucrose, starch, and plant leaves. Such methods could decrease the use of hazardous chemicals in chemical processes and reduce or eliminate undesirable products during the synthesis process. The employment of micro-organisms for the green synthesis of nanoparticles is also described. In addition, the use of nanomaterials as photocatalysts, Fentons catalysts, and disinfectants is reported for environmental remediation including the degradation of organic contaminants and the inactivation of pathogenic micro-organisms in water. Finally, the importance of immobilization of nanomaterials onto substrates for their sustainable application to environmental remediation, in particular, contaminated water and wastewater treatment is presented.

Nanoscale materials for organohalide degradation via reduction pathways

Abstract The unique chemical and physical properties of nanoscale materials have led to important roles in several scientific and technological fields. Environmental chemistry processes have benefited from the enhanced reactivity of nanoscale particles relative to their bulk counterparts with contaminants. Here, we describe recent advances in the synthesis and characterization of metallic and bimetallic nanoparticles that have been effective toward degrading toxic organohalide contaminants. We then review the degradation mechanisms involved in the reactions of nanoscale particles with organohalides via reduction pathways. We also discuss an emerging area – the degradation of organohalides via multi-electron transfer pathways.