A Heteroatom-Containing Functional Poly(Silylenevinylene): Synthesis, Anion Binding, and Sensing of Anion Extraction Processes.

Catalytic hydrosilylation is one of the important synthetic approaches to prepare functional organosilicon polymers. Herein, a functional silicon copolymer is constructed by polyhydrosilylation reaction between a novel 3,7-bis(dimethyl silane)-10-(2-ethylhexyl)-10H-phenothiazine monomer and a neutral tetrapyrrolic macrocycle, namely, 5,5,10,15,15,20-hexamethyl-10α, 20α-bis(4-[ethynylphenyl]) calix[4]pyrrole. The as-constructed copolymer (Mn  = 9609, PDI = 2.2) is investigated as an extractant for organic anions as their tetrabutylammonium salts under interfacial aqueous-organic (water-chloroform) conditions. In this context, a distinctive naked-eye colorimetric as well as fluorescence detection method is developed based on anion-directed hydrogen-bonding interactions. This kind of color/fluorescence monitoring serves as a handy tool for rapid screening of anion extraction processes. The copolymer exhibits high selectivity toward extraction of chloride anion. This study augments the field of polycarbosilanes, poly(silylenevinylene)s in particular, allowing access to a new application window that can be further advanced with good grace in near future.

Carbon Nanodots as Peroxidase Nanozymes for Biosensing.

'Nanozymes', a term coined by Scrimin, Pasquato, and co-workers to describe nanomaterials with enzyme-like characteristics, represent an exciting and emerging research area in the field of artificial enzymes. Indubitably, the last decade has witnessed substantial advancements in the design of a variety of functional nanoscale materials, including metal oxides and carbon-based nanomaterials, which mimic the structures and functions of naturally occurring enzymes. Among these, carbon nanodots (C-dots) or carbon quantum dots (CQDs) offer huge potential due to their unique properties as compared to natural enzymes and/or classical artificial enzymes. In this mini review, we discuss the peroxidase-like catalytic activities of C-dots and their applications in biosensing. The scope intends to cover not only the C-dots but also graphene quantum dots (GQDs), doped C-dots/GQDs, carbon nitride dots, and C-dots/GQDs nanocomposites. Nevertheless, this mini review is designed to be illustrative, not comprehensive.

Graphene-Based Nanomaterials as Efficient Peroxidase Mimetic Catalysts for Biosensing Applications: An Overview.

"Artificial enzymes", a term coined by Breslow for enzyme mimics is an exciting and promising branch of biomimetic chemistry aiming to imitate the general and essential principles of natural enzymes using a variety of alternative materials including heterogeneous catalysts. Peroxidase enzymes represent a large family of oxidoreductases that typically catalyze biological reactions with high substrate affinity and specificity under relatively mild conditions and thus offer a wide range of practical applications in many areas of science. The increasing understanding of general principles as well as intrinsic drawbacks such as low operational stability, high cost, difficulty in purification and storage, and sensitivity of catalytic activity towards atmospheric conditions of peroxidases has triggered a dynamic field in nanotechnology, biochemical, and material science that aims at joining the better of three worlds by combining the concept adapted from nature with the processability of catalytically active graphene-based nanomaterials (G-NMs) as excellent peroxidase mimetic catalysts. This comprehensive review discusses an up-to-date synthesis, kinetics, mechanisms, and biosensing applications of a variety of G-NMs that have been explored as promising catalysts to mimic natural peroxidases.

Graphene-based nanomaterials as heterogeneous acid catalysts: a comprehensive perspective.

Acid catalysis is quite prevalent and probably one of the most routine operations in both industrial processes and research laboratories worldwide. Recently, "graphene", a two dimensional single-layer carbon sheet with hexagonal packed lattice structure, imitative of nanomaterials, has shown great potential as alternative and eco-friendly solid carbocatalyst for a variety of acid-catalyzed reactions. Owing to their exceptional physical, chemical, and mechanical properties, graphene-based nanomaterials (G-NMs) offer highly stable Brønsted acidic sites, high mass transfer, relatively large surface areas, water tolerant character, and convenient recoverability as well as recyclability, whilst retaining high activity in acid-catalyzed chemical reactions. This comprehensive review focuses on the chemistry of G-NMs, including their synthesis, characterization, properties, functionalization, and up-to-date applications in heterogeneous acid catalysis. In line with this, in certain instances readers may find herein some criticisms that should be taken as constructive and would be of value in understanding the scope and limitations of current approaches utilizing graphene and its derivatives for the same.

Colorimetric recognition of hydrazine in aqueous solution by a bromophenol blue-tethered ion-pair-like ratiometric probe.

Hydrazine or hydrazine hydrate (N2H4·H2O) is a potential neurotoxin and has several mutagenic effects in physiological systems. Therefore, the development of synthetic organic probes that are sensitive and selective to hydrazine is of tremendous importance. Unfortunately, however, the hydrazine-selective sensing probes that rely upon minimum usage of the organic solvents (≤5%, v/v) are still rarer. In this work, an ion-pair-like mono acetate derivative of bromophenol blue has been developed as a fairly selective ratiometric probe for the naked-eye recognition of hydrazine in a solution of tris buffer and EtOH (19:1, v/v) at physiological pH. The chromogenic signalling relies upon hydrazine-induced cleavage of an ester moiety of the probe to its resonance stabilized quinonoid form, resulting in momentous variations in its spectrophotometric profile. Meanwhile, the colour of the probe solution changed from mustard yellow to blue within few minutes. This sensing assay could be successfully applied in the recognition of hydrazine in real environmental and pharmaceutical samples with satisfactory recoveries. Given the cost-effectiveness, simplicity and versatility, for instance, direct analysis of colorimetric probes, it is reasonable to propose that the present method can serve as a complementary method for prompt inspection of hydrazine in boiler feed water.

A Hydrosilylation Approach to Silicon-Bridged Functional Dipyrromethanes: Introducing Silicon to A New Arena.

Two silylene-spaced ((E)-vinylsilyl)anthracene-dipyrromethane dyads have been designed and synthesized by RhCl(PPh3 )3 -catalyzed hydrosilylation reactions of 5-methyl-5'-(ethynylaryl)dipyrromethanes with (9-Anthryl)-dimethylsilane. The complexation studies of dyads toward different anions have also been performed, which reveal that dyads exhibit a highly selective response towards fluoride anion attributable to both hydrogen-bonding and pentacoordination phenomena. This dual-mode fluoride recognition event is unprecedented and may pave the way for future developments in the areas of porphyrinoids, organosilicon, polymer, and supramolecular chemistry.

Syntheses of calix[4]pyrroles by amberlyst-15 catalyzed cyclocondensations of pyrrole with selected ketones.

A facile and efficient protocol is reported for the synthesis of calix[4]pyrroles and N-confused calix[4]pyrroles in moderate to excellent yields by reaction of dialkyl or cycloalkyl ketones with pyrrole catalyzed by reusable Amberlyst(TM)-15 under eco-friendly conditions.

A novel graphene-based label-free fluorescence 'turn-on' nanosensor for selective and sensitive detection of phosphorylated species in biological samples and living cells.

A novel label-free fluorescence 'turn-on' nanosensor has been developed for highly selective and sensitive detection of phosphorylated species (Ps) in biological samples and living cells. The design strategy relies on the use of Ti(4+)-immobilized polydopamine (PDA) coated reduced graphene oxide (rGO@PDA-Ti(4+)) that serves as an attractive platform to bind riboflavin 5'-monophosphate molecules (FMNs) through ion-pair interactions between phosphate groups and Ti(4+). The as-prepared rGO@PDA-Ti(4+)-FMNs (nanosensor), fluoresce only weakly due to the ineffective Förster resonance energy transfer between the FMNs and rGO@PDA-Ti(4+). The experimental findings revealed that the microwave-assisted interaction of the nanosensor with α-, ß-casein, ovalbumin, human serum, non-fat milk, egg white, and living cells (all containing Ps) releases FMNs (due to the high formation constant between phosphate groups and Ti(4+)), leading to an excellent fluorescence 'turn-on' response. The fluorescence spectroscopy, confocal microscopy, and MALDI-TOF MS spectrometry were used to detect Ps both qualitatively and quantitatively. Under the optimized conditions, the nanosensor showed a detection limit of ca. 118.5, 28.9, and 54.8 nM for the tryptic digests of α-, ß-casein and ovalbumin, respectively. Furthermore, the standard addition method was used as a bench-mark proof for phosphopeptide quantification in egg white samples. We postulate that the present quantitative assay for Ps holds tremendous potential and may pave the way to disease diagnostics in the near future.

A highly selective phenothiazine-based fluorescence 'turn-on' indicator based on cyanide-promoted novel protection/deprotection mechanism.

A cyanide anion (CN(-))-triggered deprotection of NH-protected phenothiazine, (E)-10-(10H-phenothiazin-3'-yl)propenal, has been discovered as a novel mechanism for the highly selective fluorescence detection of CN(-) under ambient conditions. The present protocol may pave the way for its broad application in organic synthesis in the near future.

Graphene-based nanomaterials as molecular imaging agents.

Molecular imaging (MI) is a noninvasive, real-time visualization of biochemical events at the cellular and molecular level within tissues, living cells, and/or intact objects that can be advantageously applied in the areas of diagnostics, therapeutics, drug discovery, and development in understanding the nanoscale reactions including enzymatic conversions and protein-protein interactions. Consequently, over the years, great advancement has been made in the development of a variety of MI agents such as peptides, aptamers, antibodies, and various nanomaterials (NMs) including single-walled carbon nanotubes. Recently, graphene, a material popularized by Geim & Novoselov, has ignited considerable research efforts to rationally design and execute a wide range of graphene-based NMs making them an attractive platform for developing highly sensitive MI agents. Owing to their exceptional physicochemical and biological properties combined with desirable surface engineering, graphene-based NMs offer stable and tunable visible emission, small hydrodynamic size, low toxicity, and high biocompatibility and thus have been explored for in vitro and in vivo imaging applications as a promising alternative of traditional imaging agents. This review begins by describing the intrinsic properties of graphene and the key MI modalities. After which, we provide an overview on the recent advances in the design and development as well as physicochemical properties of the different classes of graphene-based NMs (graphene-dye conjugates, graphene-antibody conjugates, graphene-nanoparticle composites, and graphene quantum dots) being used as MI agents for potential applications including theranostics. Finally, the major challenges and future directions in the field will be discussed.

Rapid identification of trimethyl and triethyl amines using sulphonic acidic ionic liquids: A time-of-flight secondary ion mass spectrometry study of fragmentation reactions.

The time-of-flight secondary ion mass spectrometry (TOF-SIMS) has emerged as a powerful tool for the unswerving detection of biomolecules, in particular, proteins and peptides. To date, there is very little information available on the direct determination of trimethyl/triethyl amines using TOF-SIMS. One major hurdle in this regard is an ultrahigh vacuum system, usually needed in TOF-SIMS, which hampers its usability to trimethyl/triethyl amines owing to their high evaporation rate. We designed an efficient and sensitive protocol for rapid identification and sensitive determination of tertiaryalkyl amines using TOF-SIMS. The amines were derivatized by reaction with 1,4-butane sultone and sulphuric acid sequentially to afford the corresponding sulphonic acidic ionic liquids (ILs). The TOF-SIMS analysis of these task-specific ILs (TSILs) was carried out in both positive and negative polarity. The positive ion mass spectra of TSILs showed sharp fragmented peaks for tertiaryalkyl amines at typical level and up to 10ppm. The possible mechanism for different fragmentation pathways in positive polarity was discussed.