Showing papers by "Thalappil Pradeep published in 2019"
TL;DR: This Account presents recent advancements on different possibilities of supramolecular interactions in atomically precise cluster systems that can occur at different length scales and discusses how variation in intercluster interactions can lead to polymorphic crystals, which are observable in single-crystal X-ray diffraction.
Abstract: ConspectusSupramolecular chemistry is a major area of chemistry that utilizes weaker non-covalent interactions between molecules, including hydrogen bonding, van der Waals, electrostatic, π···π, and C–H···π interactions. Such forces have been the basis of several molecular self-assemblies and host–guest complexes in organic, inorganic, and biological systems. Atomically precise nanoclusters (NCs) are materials of growing interest that display interesting structure–property correlations. The evolving science of such systems reaffirms their molecular behavior. This gives a possibility of exploring their supramolecular chemistry, leading to assemblies with similar or dissimilar cluster molecules. Such assemblies with compositional, structural, and conformational precision may ultimately result in cluster-assembled hybrid materials. In this Account, we present recent advancements on different possibilities of supramolecular interactions in atomically precise cluster systems that can occur at different length ...
133 citations
TL;DR: The optical spectrum of the mixture showed unique features which were in good agreement with the results from time-dependent density functional theory (TD-DFT) and the presence of two entities in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry.
Abstract: Two ligand-protected nanoscale silver moieties, [Ag46 (SPhMe2 )24 (PPh3 )8 ](NO3 )2 and [Ag40 (SPhMe2 )24 (PPh3 )8 ](NO3 )2 (abbreviated as Ag46 and Ag40 , respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co-crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag32 S24 P8 , which is reminiscent of fullerenes, and it encapsulates a well-studied core, Ag14 and a completely new core, Ag8 , which correspond to a face-centered cube and a simple cube, respectively, resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time-dependent density functional theory (TD-DFT).
75 citations
TL;DR: In-depth structural elucidation and density functional theory calculations suggest that the cluster is a superatom with four magic electrons, which is divalent and contains four free electrons.
Abstract: We introduce a cluster coprotected by thiol and diphosphine ligands, [Ag22(dppe)4(2,5-DMBT)12Cl4]2+ (dppe = 1,2-bis(diphenylphosphino)ethane; 2,5-DMBT= 2,5-dimethylbenzenethiol), which has an Ag10 core encapsulated by an Ag12(dppe)4(2,5-DMBT)12Cl4 shell. The Ag10 core comprises two Ag5 distorted trigonal bipyramidal units and is uncommon in Au and Ag nanoclusters. The electrospray ionization mass spectrum reveals that the cluster is divalent and contains four free electrons. An uncommon crystallization-induced enhancement of emission is observed in the cluster. The emission is weak in the solution and amorphous states. However, it is enhanced 12 times in the crystalline state compared to the amorphous state. A detailed investigation of the crystal structure suggests that well-arranged C–H···π and π···π interactions between the ligands are the major factors for this enhanced emission. Further, in-depth structural elucidation and density functional theory calculations suggest that the cluster is a superatom...
61 citations
TL;DR: It is found that molecular mobility and interactions play crucial roles in the formation of CHs, even though there is no external pressure to force cage formation, implying that CHs can exist in extreme low-pressure environments present in the ISM.
Abstract: Clathrate hydrates (CHs) are ubiquitous in earth under high-pressure conditions, but their existence in the interstellar medium (ISM) remains unknown. Here, we report experimental observations of the formation of methane and carbon dioxide hydrates in an environment analogous to ISM. Thermal treatment of solid methane and carbon dioxide–water mixture in ultrahigh vacuum of the order of 10 −10 mbar for extended periods led to the formation of CHs at 30 and 10 K, respectively. High molecular mobility and H bonding play important roles in the entrapment of gases in the in situ formed 5 12 CH cages. This finding implies that CHs can exist in extreme low-pressure environments present in the ISM. These hydrates in ISM, subjected to various chemical processes, may act as sources for relevant prebiotic molecules.
36 citations
TL;DR: Chakraborty et al. as mentioned in this paper reviewed recent advances in applying mass spectrometry to solid-state materials, specifically nanoclusters of noble metals, and summarise the successes of mass-spectrometry in determining properties such as ionization energy and electronic structure in emerging materials.
Abstract: Mass spectrometry (MS), a hundred-year-old subject, has been a technique of profound importance to molecular science. Its impact in solid-state materials science has not been evident, although many materials of modern science, such as fullerenes, have their origins in MS. Of late, mass spectrometric interface with materials is increasingly strengthened with advances in atomically precise clusters of noble metals. Advances in instrumentation along with recent developments in synthetic approaches have expanded the chemistry of clusters, and new insights into matter at the nanoscale are emerging. High-resolution MS coupled with soft ionization techniques enable efficient characterization of atomically precise clusters. Apart from that, techniques such as ion mobility, tandem MS, etc. reveal structural details of these systems. Growth, nucleation, and reactivity of clusters are also probed by MS. Some of the recent advancements in this field include the development of new hyphenated techniques. Finer structural details may be obtained by coupling MS with spectroscopic tools, such as photoelectron spectroscopy, vacuum ultraviolet spectroscopy, etc. With such advancements in instrumentation, MS can evolve into a universal tool for the characterization of materials. The present review captures highlights of this area. Recent advances in mass spectrometry have broadened the range of materials that it can be used to analyse, including solids. Mass spectrometry determines the composition of a material by measuring the mass of ions. Papri Chakraborty and Thalappil Pradeep from the Indian Institute of Technology Madras, Chennai, review recent advances in the efficiency and precision of this technology. Early work in mass spectrometry focussed on gases. The authors look back over recent advances in applying mass spectrometry to solid-state materials, specifically nanoclusters of noble metals. They summarise the successes of mass spectrometry in determining properties such as ionization energy and electronic structure in emerging materials. Much of this success has come from using so-called hyphenated techniques: combining mass spectrometry with methods such as ion mobility, chromatography, photoelectron spectroscopy and optical spectroscopy. Mass spectrometry, coupled with soft ionization methods, in conjunction with associated techniques such as tandem mass spectrometry, ion mobility and spectroscopies of sorts, has become a powerful tool for the characterization of advanced materials.
35 citations
TL;DR: The nature of the M-L interfaces, i.e., the oxidation state of metal atoms, structure of the ligand, M- L bonding network, and so forth, plays a key role in the chemical reactivity of clusters.
Abstract: We discuss the role of the metal–ligand (M–L) interfaces in the chemistry of ligand-protected, atomically precise noble metal clusters, a new and expanding family of nanosystems, in solution as well as in the gas phase. A few possible mechanisms by which the structure and dynamics of M–L interfaces could trigger intercluster exchange reactions are presented first. How interparticle chemistry can be a potential mechanism of Ostwald ripening, a well-known particle coarsening process, is also discussed. The reaction of Ag59(2,5-DCBT)32 (DCBT = dichlorobenzenethiol) with 2,4-DCBT leading to the formation of Ag44(2,4-DCBT)30 is presented, demonstrating the influence of the ligand structure in ligand-induced chemical transformations of clusters. We also discuss the structural isomerism of clusters such as Ag44(SR)30 (−SR = alkyl/aryl thiolate) in the gas phase wherein the occurrence of isomerism is attributed to the structural rearrangements in the M–L bonding network. Interfacial bonding between Au25(SR)18 clu...
32 citations
04 Jun 2019
TL;DR: In this article, the authors proposed wearable electronics have gained momentum in the past few years, there is a dire need for smart, responsive, and, most importantly, affordable sensors for biological monitoring.
Abstract: As wearable electronics have gained momentum in the past few years, there is a dire need for smart, responsive, and, most importantly, affordable sensors for biological monitoring. One such noninva...
30 citations
TL;DR: An unprecedented growth mechanism for the formation of silver NCs mediated by silver-thiolate intermediates is presented and suggests selective crystallization in the co-crystal.
Abstract: We present an example of an interparticle reaction between atomically precise nanoclusters (NCs) of the same metal, resulting in entirely different clusters. In detail, the clusters [Ag12(TBT)8(TFA)5(CH3CN)]+ (TBT = tert-butylthiolate, TFA = trifluoroacetate, CH3CN = acetonitrile) and [Ag18(TPP)10H16]2+ (TPP = triphenylphosphine) abbreviated as Ag12 and Ag18, respectively, react leading to [Ag16(TBT)8(TFA)7(CH3CN)3Cl]+ and [Ag17(TBT)8(TFA)7(CH3CN)3Cl]+, abbreviated as Ag16 and Ag17, respectively. The two product NCs crystallize together as both possess the same metal chalcogenolate shell, composed of Ag16S8, making them indistinguishable. The occupancies of Ag16 and Ag17 are 66.66 and 33.33%, respectively, in a single crystal. Electrospray ionization mass spectrometry (ESI MS) of the reaction product and a dissolved crystal show the population of Ag16 and Ag17 NCs to be in a 1:1 and 2:1 ratio, respectively. This suggests selective crystallization in the cocrystal. Time-dependent ESI MS was employed to understand the formation of product clusters by monitoring the reaction intermediates formed in the course of the reaction. We present an unprecedented growth mechanism for the formation of silver NCs mediated by silver thiolate intermediates.
30 citations
TL;DR: The results acquired indicate an immense potential for scaling up the photoreactor as a sustainable tertiary treatment technology in water treatment plants.
28 citations
TL;DR: The desorption electrospray ionization mass spectrometry imaging results indicated a clear tissue localization of the various indole alkaloids, in fruits, leaves and roots of R. tetraphylla.
27 citations
TL;DR: Time-lapse observations have shown that laser-induced changes in the plasmonic properties of AgNPs resulted in the appearance of SERS, and it is shown that the release of silver ions by silver nanoparticles can be the probable reason for their plAsmonic changes.
Abstract: We report simultaneous plasmonic scattering and Raman spectroscopic observations of single citrate capped silver nanoparticles (AgNPs) which exhibit surface enhanced Raman scattering (SERS) upon meeting specific conditions induced by laser (532 nm) exposure. We show that nanoparticles which are not initially SERS active become SERS active by laser-induced reshaping/reorientation. A set-up developed for these observations enabled in situ high speed time-lapse characterization using plasmonic and Raman spectroscopies in conjunction with dark-field microscopy (DFM). Changes in the AgNPs were confirmed by monitoring plasmonic scattering spectra and DFM images. Time-lapse observations have shown that laser-induced changes in the plasmonic properties of AgNPs resulted in the appearance of SERS. Spectral matching between plasmon resonance and downward molecular vibronic transitions for molecules adsorbed on the surface of plasmonic nanomaterials is attributed to the nanoparticle SERS. We have further shown that the release of silver ions by silver nanoparticles can be the probable reason for their plasmonic changes. Gold nanoparticles inert to such mild (850 μW, 532 nm) laser-induced changes do not exhibit the appearance of SERS.
TL;DR: In this article, the authors report various functionalized microcellulose-reinforced 2-line ferrihydrite composites which show outstanding As(III) and As(V) adsorption capacities.
Abstract: Arsenicosis was recognized over 104 years ago. Elevated arsenic (As) concentrations in water is faced by about 200 million people worldwide and has become one of the biggest challenges in the context of water purification. Providing sustainable and affordable solutions to tackle this menace is a need of the hour. Adsorption on advanced materials is increasingly being recognized as a potential solution. Here, we report various functionalized microcellulose-reinforced 2-line ferrihydrite composites which show outstanding As(III) and As(V) adsorption capacities. Green synthesis of the composite yields granular media with high mechanical strength which show faster adsorption kinetics in a wide pH range, irrespective of the presence of other interfering ions in water. The composites and their interaction with As(III) and As(V) were studied by XRD, HRTEM, SEM, XPS, Raman, TG, and IR spectroscopy. Performance of the media in the form of cartridge reaffirms its utility for point-of-use water purification. We show...
08 Oct 2019
TL;DR: The crystal structure of a supramolecular coassembly of a red luminescent silver cluster was reported in this paper, where it was shown that the structure of the cluster is similar to the one described in this paper.
Abstract: We report the crystal structure of a supramolecular coassembly of a red luminescent silver cluster, [Ag29(BDT)12(TPP)4]3– (referred to as Ag29) (BDT, 1,3-benzene dithiol; TPP, triphenyl phosphine),...
TL;DR: In addition to insulin resistance (HOMA-IR), hyperandrogenemia is an independent predictor of NAFLD in women with PCOS in a prospective, cross-sectional study at a tertiary care hospital from South India.
Abstract: Aims To find the prevalence and predictors of nonalcoholic fatty liver disease (NAFLD) in Asian Indian polycystic ovary syndrome (PCOS) women. Materials and methods This is a prospective, cross-sectional study conducted at a tertiary care hospital from South India. Sixty women fulfilling the Rotterdam (2003) criteria for PCOS were recruited for the study. All participants were evaluated with ultrasound abdomen for fatty liver and additional biochemical investigations including fasting plasma glucose, postprandial plasma glucose, serum insulin, lipid profile and liver function tests. Results The mean age of the study population was 24.06 ± 5.9 (range: 15–39) years. Oligomenorrhea, hirsutism and acne were present in 58 (96.7%), 37 (61.7%) and 33 (55%) women. Mean BMI of the study population was 29.5 ± 5.28 (range: 19.95 to 45.44) kg/m2. Fifty (83.3%) women were obese (BMI: ≥ 25 kg/m2). Twenty-three (38.3%) women with PCOS had NAFLD. Three women each had isolated elevation of alanine transaminase (ALT) and aspartate transaminases (AST) whereas three women had elevation of both. All women with elevated transaminases had NAFLD. By univariate analysis, factors associated with NAFLD were serum total cholesterol, serum insulin, HOMA-IR, hyperandrogenism, ALT and AST. On multiple regression analysis using linear regression, HOMA-IR and hyperandrogenemia were the only significant predictors of NAFLD. Conclusion Our study reports NAFLD in more than one third of Asian Indian women with PCOS. In addition to insulin resistance (HOMA-IR), hyperandrogenemia is an independent predictor of NAFLD in women with PCOS.
TL;DR: This novel technique was used to detect melamine in adulterated milk, whose detection at the ppt level in milk normally needs sophisticated instruments, a larger amount of sample, and a complex sampling procedure, including further purification and separation.
Abstract: A new kind of ambient ionization method named superhydrophobic preconcentration paper spray ionization mass spectrometry (SHPPSI MS) is introduced, where superhydrophobicity and paper spray mass spectrometry (PS MS) are coupled. The SHPPSI MS requires only microliter amounts of analyte solutions, allows easy sampling procedure, and provides high sensitivity for a diverse array of analytes. It can be used to detect food adulteration at extremely low concentrations. The experimental methodology involves modifying one of the surfaces of a triangularly cut filter paper to make it acquire low surface energy by drop casting a green and ecofriendly superhydrophobic coating material over it followed by drying. A micrometer scale defect was made at close proximity to one of the tips of the paper using a pin. Preconcentration of the sample was accomplished by allowing a 10 μL droplet of an aqueous solution of the analyte to stand at the defect followed by drying naturally. The dried paper was used as the substrate ...
TL;DR: Rapid isotopic exchange reveals the solution-state dynamics existing in nanoparticles, very similar to that in H2O and D2O, as two isotopically pure silver clusters made of 107Ag and 109Ag are mixed.
Abstract: Rapid solution-state exchange dynamics in nanoscale pieces of matter is revealed, taking isotopically pure atomically precise clusters as examples. As two isotopically pure silver clusters made of 107Ag and 109Ag are mixed, an isotopically mixed cluster of the same entity results, similar to the formation of HDO, from H2O and D2O. This spontaneous process is driven by the entropy of mixing and involves events at multiple time scales.
TL;DR: In this article, a method for synthesizing different phases of copper sulphide nanostructures using electrospray deposition (ESD) of molecular sulphur in the form of droplets on metallic copper surfaces under ambient conditions was introduced.
Abstract: We introduce a new and simple method for synthesizing different phases of copper sulphide nanostructures using electrospray deposition (ESD) of molecular sulphur in the form of droplets on metallic copper surfaces under ambient conditions. Different phases of copper sulphide nanostructures were created by controlling the deposition time. Time dependent electron microscopy reveals conversion of the Cu2S nanopyramids to Cu1.8S platelets during the course of ESD. In the beginning of deposition, direct interaction between sulphur ions and metallic copper creates Cu2S nanopyramids followed by subsequent slow diffusion of sulphur leading to the formation of copper deficient Cu1.8S platelets. A detailed characterization of both the nanostructures was performed by using different microscopic and spectroscopic tools such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, powder X-ray diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS). We have also studied the optical properties of these nanostructures in both UV-Vis and near infrared (NIR) regions. The characteristic broad peaks in the UV-Vis region of Cu2S nanopyramids indicate the photosensitive nature of the material. A positive photocurrent response was observed from the Cu2S nanopyramids under electrochemical conditions, while Cu1.8S nanostructure shows an intense localized surface plasmon (LSPR) peak in the NIR region indicating its metallic nature. Current–voltage (I–V) measurements showed metallic conductivity in them.
TL;DR: Striking voltammetry-induced change in morphology and phase of as-prepared Mn-based electrodes during As sensing and the simultaneous phase evolution of active material occurring through multiple stripping cycles are reported.
Abstract: A simple, one-step electrodeposition approach has been used to fabricate MnOx on an indium-doped tin oxide substrate for highly sensitive As3+ detection. We report an experimental limit of detectio...
TL;DR: In this paper, single-crystal X-ray diffraction is used to determine the structure of monolayer-protected coinage metal clusters in solid state, which is not readily applicable to the characte...
Abstract: Although single-crystal X-ray diffraction is a proven technique to determine the structure of monolayer-protected coinage metal clusters in solid state, it is not readily applicable to the characte...
TL;DR: In this paper, the authors probed the interaction between Au38@BSA and various heavy metal ions using luminescence spectroscopy and found that Au38-BSA showed luminecence enhancement upon interaction with Cd2+ and Pb2+.
Abstract: We probed the interaction between Au38@BSA and various heavy metal ions using luminescence spectroscopy. Interestingly, Au38@BSA showed luminescence enhancement upon interaction with Cd2+ and Pb2+ ...
TL;DR: In this article, the formation of tetrahydrofuran (THF) was reported in ultra-high vacuum (UHV) conditions, where CHs typically nucleate under high-pressure conditions.
Abstract: Clathrate hydrates (CHs) typically nucleate under high-pressure conditions, but their existence in ultrahigh vacuum (UHV) is an open question. Here, we report the formation of tetrahydrofuran (THF)...
TL;DR: In this article, a new synthetic protocol is introduced which preserves the secondary structure of protecting proteins encapsulating a luminescent atomically-precise silver cluster, without using any reducing agent, which results in minimal alteration of the protein structure during cluster growth.
Abstract: A new synthetic protocol is introduced which preserves the secondary structure of protecting proteins encapsulating a luminescent atomically-precise silver cluster. This was achieved by using a preformed triphenylphosphine (TPP)-protected silver cluster as the precursor forming bovine serum albumin (BSA)- and human serum albumin (HSA)-protected Ag18 clusters. This is the first example of the formation of luminescent protein-protected clusters in a neutral medium, without using any reducing agent, which results in minimal alteration of the protein structure during cluster growth. The cluster formed showed exceptional stability, unlike other silver clusters of this class. The formation of these red luminescent clusters was visualized by UV–vis and photoluminescence spectroscopy. The identification of Ag18 core was made through matrix-assisted laser desorption ionization mass spectrometry (MALDI MS), and a plausible mechanism of the formation was identified by monitoring the systematic growth of the cluster ...
TL;DR: Low-cost nanocellulose-aluminium oxyhydroxide nanocomposites functionalized with silver nanoparticles provide insights for designing freshwater purification systems that utilize silver-releasing materials and indicate that an increase of chloride concentration leads to a substantial reduction of antibacterial efficiency, even within chloride concentrations found in freshwaters.
Abstract: The availability of microbially-safe drinking water is a challenge in many developing regions. Due to the well-known antibacterial effect of silver ions, materials used for their controlled release have been widely studied for point-of-use water disinfection. However, even if it is in principle known that chloride anions can suppress the antibacterial efficiency of silver, the majority of previous studies, surprisingly, have not focused on chloride concentrations relevant for freshwaters and thus for practical applications. Here, we prepared low-cost nanocellulose-aluminium oxyhydroxide nanocomposites functionalized with silver nanoparticles. Field samples obtained from Chennai, India were used as a guideline for choosing relevant chloride concentrations for the antibacterial studies, i.e., 10, 90, and 290 ppm. The antibacterial performance of the material against Escherichia coli and Bacillus subtilis was demonstrated and the influence of chloride concentration on the antibacterial effect was studied with E. coli. A 1 h contact time led to bacterial reductions of 5.6 log10, 2.9 log10, and 2.2 log10, respectively. This indicates that an increase of chloride concentration leads to a substantial reduction of antibacterial efficiency, even within chloride concentrations found in freshwaters. This work enables further insights for designing freshwater purification systems that utilize silver-releasing materials.
TL;DR: This work performed an intercluster reaction between silver clusters and produced highly ionizable Ag-S-type clusters and examined their formation by mass spectrometry.
Abstract: Recent reports have shown that the intercluster reaction is a new synthetic strategy to prepare alloy clusters. In this work, we performed an intercluster reaction between silver clusters and produced highly ionizable Ag-S-type clusters; we examined their formation by mass spectrometry. [Ag18(TPP)10H16]2+ (Ag18), a highly reactive hydride and phosphine-protected silver cluster, was used as a sacrificial cluster in this synthesis. An intercluster reaction between Ag18 and smaller silver-chalcogenolate clusters (SCC) resulted in a new cluster, [Ag34S3SBB20(CF3COO)6]2+. The cluster showed an NIR emission at around 1100 nm. The cluster composition was confirmed by high-resolution electrospray ionization mass spectrometry (ESI-MS), thermogravimetry (TGA), and X-ray photoelectron spectroscopy (XPS).
TL;DR: The first example of a covalently bound dimer of monolayer protected atomically precise silver nanocluster [Ag25(DMBT)18] is reported, which could be important to design new cluster assembled materials with composite properties.
TL;DR: In this paper, the degradation of polytetrafluoroethylene (PTFE) in water in the presence of common metals and crosstalk has been reported, which is the most extensively used chemically inert and thermally stable polymer.
Abstract: Polytetrafluoroethylene (PTFE) is probably the most extensively used chemically inert and thermally stable polymer. We report the degradation of PTFE in water in the presence of common metals and c...
TL;DR: In this paper, a waterborne, fluorine-free, robust superhydrophobic material was synthesized at room temperature through a one-step chemical-modification process, which exhibits moisture and CO2 capturing capability.
Abstract: Mimicking natural phenomena is probably the best way to explore smartness. Over the years this has made Mother Nature an idol of architecture. Among many others, surfaces of various biological species having interesting nonwetting characteristics have attracted both industry and academia and have become some of the intensely pursued research areas because of their enormous potential in various domains.[1] Although several methodologies have been introduced to fabricate these surfaces, complicated multistep processes, limitation in large area production, durability, etc., have restricted their use in everyday life.[2] Recently, a few such robust liquid repelling surfaces have been reported.[2c,3] However, in most of the cases, achieving such a property involves the use of 1) fluorine-containing chemicals (offering low surface energy) and 2) hazardous organic solvents.[3a,4] While fluorinated hydrocarbons can lead to bioaccumulation and toxicity, the use of organic solvents increases environmental concerns.[5] Recently, a few superhydrophobic materials have also been designed with reduced environmental impact.[6] For example, Chen and co-workers have demonstrated the fabrication of a fluorine-free robust superhydrophobic surface, but organic solvents were used in the process.[7] We have shown the fabrication of organic-solvent-free superhydrophobic materials that contain fluorinated molecules.[8] Therefore, designing a water-based fluorine-free robust low energy materials at ambient conditions is important from the perspective of reduced environmental impact and industrial significance. Imparting new properties such as conductivity, chemical sensitivity, etc., especially to nonwettable materials is important.[9] For example, introduction of carbon-based materials such as graphite, reduced-graphene, and carbon nanotubes to enhance the mechanical, thermal, and electrical conductivity,[10] incorporation of inorganic nanoparticles such as TiO2, and ZnO to impart biodegradation, etc.,[2a,11] to superhydrophobic surfaces are well known. However, in most of the cases, these modified surfaces were developed through the incorporation of different micro/nanomaterials. In contrast, fabrication of superhydrophobic materials having molecularly grafted functionalities Recent progress in the field of superhydrophobic materials has proven their potential to solve many problems of the contemporary society. However, the use of such materials to capture moisture and CO2 from air, to help reduce the impact of global climate change is not explored. In addition, most of the time, fabrication of these materials needs organic solvents and fluorinated molecules involving multiple steps that hinder the use of nonwettable materials in everyday life. Herein, a waterborne, fluorinefree, robust superhydrophobic material synthesized at room temperature through a one-step chemical-modification process is reported, which exhibits moisture and CO2 capturing capability. While covalently grafted low surface energy hydrocarbon molecules control the bulk superhydrophobicity, the incorporated amine functionalities facilitate moisture and CO2 adsorption as these molecules (H2O and CO2) can easily diffuse through hydrocarbon assemblies. Being polar, H2O molecules are observed to readily interact with amine groups and favor the adsorption process. Synthesized material shows an approximate CO2 adsorption of 480 ppm (10.90 mmol L−1) in ambient conditions having 75% humidity. Multifunctionality along with durability of this material will help expand the applications of superhydrophobic materials. Superhydrophobic Surfaces
TL;DR: Reduced analysis time and improved reproducibility of the data in every analysis, which is generally difficult in SERS, the amount of AgNPs required is an order of magnitude lower in this method, which could also be used to probe the real-time changes in molecular and biological species under ambient conditions.
Abstract: We introduce a technique called ambient electrospray deposition Raman spectroscopy (AESD RS) for rapid and sensitive surface-enhanced Raman scattering (SERS) based detection of analytes using a miniature Raman spectrometer. Using electrospray, soft landing of preformed silver nanoparticles (AgNPs) was performed for 30-40 seconds for different concentrations of analytes deposited on conducting glass slides. Using AESD RS, SERS signals were collected within 4-6 minutes, including sample preparation. Transmission electron microscopy (TEM) and dark-field microscopy (DFM) were used to characterize the preformed AgNPs before and after electrospray. We achieved the nanomolar and micromolar detection of p-mercaptobenzoic acid (p-MBA) and 2,4-dinitrotoluene (2,4-DNT), respectively. In this work, 0.3 μL of preformed AgNPs were used, which is ∼33 times less in volume than the quantity needed for conventional SERS. Quantitation of unknown concentration of analytes was also possible. A similar amount of electrosprayed AgNPs was utilized to characterize Escherichia coli (E. coli) bacteria of different concentrations. Viability of bacteria was tested using fluorescence microscopic imaging. Besides reduced analysis time and improved reproducibility of the data in every analysis, which is generally difficult in SERS, the amount of AgNPs required is an order of magnitude lower in this method. This method could also be used to probe the real-time changes in molecular and biological species under ambient conditions.
TL;DR: A novel method of coupling electrochemistry (EC) with mass spectrometry (MS) is illustrated with a paper-based electrochemical cell supported by carbon nanotubes (CNTs) and the applicability of this technique for qualitative and quantitative analyses of environmentally relevant molecules has been demonstrated.
Abstract: A novel method of coupling electrochemistry (EC) with mass spectrometry (MS) is illustrated with a paper-based electrochemical cell supported by carbon nanotubes (CNTs). The electrochemically formed ions, created at appropriate electrochemical potentials, are ejected into the gas phase from the modified paper, without the application of additional potential. The electrochemical cell was fabricated by using a rectangular CNT-coated Whatman 42 filter paper with printed electrodes, using silver paste. This was used for studying the electrochemical conversion of thiols to disulfides, and the functionalization of polycyclic aromatic hydrocarbons (PAHs), which involve S–S and C–C bond formations, respectively. We also demonstrate the versatility of the set-up by utilizing it for the detection of radical cations of metallocenes, monitoring the oxidation of sulfides through the detection of reactive intermediates, and the detection of radical cations of PAHs, all of which occur at specific applied potentials. Finally, the applicability of this technique for qualitative and quantitative analyses of environmentally relevant molecules has been demonstrated by studying the electrochemical oxidation of glucose (Glu) to gluconic acid (GlcA) and saccharic acid (SacA).
TL;DR: In this paper, an approach to create bare silver cluster Ag17+ and hydride-rich Ag17H14+ separately, as pure species uncontaminated with other entities, in the gas phase starting from a solution-phase m...
Abstract: We report an approach to create bare silver cluster Ag17+ and hydride-rich Ag17H14+ separately, as pure species uncontaminated with other entities, in the gas phase starting from a solution-phase m...