Interfacial properties of hybrid nanomaterials

A brief summary of our ongoing efforts to understand the surface properties of nanoparticles using fluorophores, namely pyrene alkanethiols, is presented. Excited state interactions were investigated by varying the length of the spacer group and the concentration of fluorophore. The flexible long alkyl chain tethering pyrene in Au-P2/Au-P3 allows free interaction between fluorophores resulting in excimer formation whereas the intermolecular interactions are limited in the Au-P1 system due to the restriction imposed by the curvature of spherical gold nanoparticle. A gradual increase in the peak intensity ratio of III/I band of the normal fluorescence of pyrene was observed indicating that the surface of nanoparticle is more polar than the bulk solvent (toluene)

Aqueous Self-Sorting in Extended Supramolecular Aggregates

Self-organization and self-sorting processes are responsible for the regulation and control of the vast majority of biological processes that eventually sustain life on our planet. Attempts to unveil the complexity of these systems have been devoted to the investigation of the binding processes between artificial molecules, complexes or aggregates within multicomponent mixtures, which has facilitated the emergence of the field of self-sorting in the last decade. Since, artificial systems involving discrete supramolecular structures, extended supramolecular aggregates or gel-phase materials in organic solvents or—to a lesser extent—in water have been investigated. In this review, we have collected diverse strategies employed in recent years to construct extended supramolecular aggregates in water upon self-sorting of small synthetic molecules. We have made particular emphasis on co-assembly processes in binary mixtures leading to supramolecular structures of remarkable complexity and the influence of different external variables such as solvent and concentration to direct recognition or discrimination processes between these species. The comprehension of such recognition phenomena will be crucial for the organization and evolution of complex matter

Colorimetric Assay for Determination of Lead (II) Based on Its Incorporation into Gold Nanoparticles during Their Synthesis

In this report, we present a new method for visual detection of Pb2+. Gold nanoparticles (Au-NPs) were synthesized in one step at room temperature, using gallic acid (GA) as reducer and stabilizer. Pb2+ is added during the gold nanoparticle formation. Analysis of Pb2+ is conducted by a dual strategy, namely, colorimetry and spectrometry. During Au-NPs synthesis, addition of Pb2+ would lead to formation of Pb-GA complex, which can induce the aggregation of newly-formed small unstable gold nanoclusters. Consequently, colorimetric detection of trace Pb2+ can be realized. As the Pb2+ concentration increases, the color turns from red-wine to purple, and finally blue. This method offers a sensitive linear correlation between the shift of the absorption band (Δλ) and logarithm of Pb2+ concentration ranging from 5.0 × 10−8 to 1.0 × 10−6 M with a linear fit coefficient of 0.998, and a high selectivity for Pb2+ detection with a low detection limit down to 2.5 × 10−8 M

Contamination controlled by surface modification (Surfaces of mining applications)

The collection of dust particles in engines causes pollution, which is a major issue for manyindustries, especially for the automotive and aerospace sectors. Dust particles enter enginesthrough various channels, such as air intake systems and mechanical gaps. After entering,these particles stick to internal parts like filters, cylinders, pistons, and valves, obstructingairflow, raising friction, and hindering healthy combustion processes. Dust pollution inengines has several serious repercussions. Among the main problems are decreased power production, higher fuel consumption, less engine efficiency, and faster wear and tear of important parts. This study investigates the surface topography of materials such as cast aluminum,aluminum, and plastic, which are commonly used as engine surfaces. In this paper, we alsoinvestigate the size of dust particles likely to be deposited on engine surfaces. These threematerials were examined using surface texture analysis based on NEWVIEWTM 9000 Zygointerferometer measurements and particle analysis provided by Digital Surf MountainLab. Tosuccessfully solve the accumulation of dust on engine surfaces, we propose using VHTenamel coating and multilayer coating. These coatings provide excellent heat resistance anddust repellence, which is critical for engine components exposed to severe environments

Contamination controlled by surface modification (Surfaces of mining applications)

The collection of dust particles in engines causes pollution, which is a major issue for manyindustries, especially for the automotive and aerospace sectors. Dust particles enter enginesthrough various channels, such as air intake systems and mechanical gaps. After entering,these particles stick to internal parts like filters, cylinders, pistons, and valves, obstructingairflow, raising friction, and hindering healthy combustion processes. Dust pollution inengines has several serious repercussions. Among the main problems are decreased power production, higher fuel consumption, less engine efficiency, and faster wear and tear of important parts. This study investigates the surface topography of materials such as cast aluminum,aluminum, and plastic, which are commonly used as engine surfaces. In this paper, we alsoinvestigate the size of dust particles likely to be deposited on engine surfaces. These threematerials were examined using surface texture analysis based on NEWVIEWTM 9000 Zygointerferometer measurements and particle analysis provided by Digital Surf MountainLab. Tosuccessfully solve the accumulation of dust on engine surfaces, we propose using VHTenamel coating and multilayer coating. These coatings provide excellent heat resistance anddust repellence, which is critical for engine components exposed to severe environments

Supramolecular Organization of Metal Nanoparticles in Solution and of Phenyleneethynylenes on Surfaces

Most of the procedures reported for the synthesis of metal nanoparticles involve the use of strong reducing agents or elevated temperatures. This limits the possibility of developing metal nanoparticle based sensors for the in situ detection of analytes. One of the objectives of the present investigations is to (i) develop newer methodologies for the synthesis of metal nanoparticles in aqueous medium at ambient conditions and (ii) their use in the detection of metal cations by taking advantage of the unique coordination ability. Ideally, biocompatible molecules which possess both the reducing and stabilizing groups are desirable for such applications. Formation of stable supramolecular assembly, by bringing metal nanoparticles close to each other, results in plasmon coupling and this strategy can be effectively utilized for the development of metal nanoparticle based sensors.Another objective of the present study is to understand the supramolecular organization of molecules on surfaces. Various noncovalent interactions between the molecules and with surface play a decisive role in their organizations. An in-depth understanding of these interactions is essential for device fabrications. Recent photophysical studies have revealed that phenyleneethynylene based molecular systems are ideal for device application. The second objective of the thesis focuses on understanding the (i) organization of phenyleneethynylenes on highly oriented pyrolytic graphite (HOPG) surface with atomic level precision and (ii) weak intermolecular interactions which drive their organization

Electrostatically driven self-assembly of CdTe nanoparticles with organic chromophores probed via Ham effect

The polarity difference between nanoparticle's surface and medium is utilized for studying electrostatically driven self-assembly; moreover, diminishing the repulsive forces via charge neutralization fosters the self-organization of QDs into 2D sheets.</p