143 research outputs found
Low-dimensional chainlike assemblies of TiO2 nanorod-stabilized Au nanoparticles RID C-5360-2009
No full textA simple and versatile light-based strategy to grow low-dimensional gold superstructures is presented; prolonged UV-irradiation of TiO2 nanorod-stabilized Au nanoparticles in organic media promotes the progressive formation of distinctive chainlike metal assemblies, namely segments of a few gold particles, 2D or quasi-1D large structures composed of interlacing lines of hundreds of metal units over areas of about 500 nm(2)
Deciphering hot- and multi-exciton dynamics in core–shell QDs by 2D electronic spectroscopies
No full text<p>2D spectroscopy datasets from PCCP 20 (2018) 18176, DOI: 10.1039/c8cp02574f</p>
<p>Dasets are in the Matlab format .mat, each one containing:</p>
<p>R(or N or T).X = 3-dimensional matrix containing 3d signal. dimensions=(w1,w3,t2)<br>
R.t= t2 axis<br>
R.f= w1=w3 axis</p>
<p> </p>
<p>R=rephasing; N=non-rephasing; T=total signal</p>
<p>2D-BC=2D photon echo in BOXCARS configuration; 2D-PP= 2D pump-probe in quasi-collinear configuration.</p>
Minerals for wastewater purification: a case study
No full textAmongst the various strategies studied to reduce polluting agents in water, both from anthropogenic and natural sources, adsorption processes are among the most widespread techniques. Layered double hydroxides (LDH, anionic adsorbers) play a fundamental role in the treatment of industrial wastewater, which often contains both anionic and cationic species. The objectives of the present study were to synthesize a (Mg, Zn) Al-NO3 LDH, and a composite between the LDH and montmorillonite (Mnt, cationic exchanger), and to test their adsorption capacity for both cationic and anionic pollutants in two different samples of industrial wastewater. The compounds were characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray powder diffraction (XRPD), Fourier-transform infrared (FT-IR) spectroscopy, differential thermal analysis/thermogravimetry (DTA-TG), and transmission electron microscopy (TEM). Results of product yields and extraction performance provided evidence that the synthesized compounds were active in the removal of various kinds of pollutants from real wastewaters. The adsorption capacity, in the case of the removal of cations varied from ~85 to 100% and from ~92 to 100% when the LDH and the LDH-Mnt, respectively, were used. The 56–100% removal of anions was instead obtained for both the adsorbents
One-Pot Synthesis of Dual Color-Emitting CDs: Numerical and Experimental Optimization towards White LEDs
No full textCarbon Dots (CDs) are fluorescent carbon-based nanoparticles that have attracted increasing attention in recent years as environment-friendly and cost-effective fluorophores. An application that can benefit from CDs in a relatively short-term perspective is the fabrication of color-converting materials in phosphor-converted white LEDs (WLEDs). In this work we present a one-pot solvothermal synthesis of polymer-passivated CDs that show a dual emission band (in the green and in the red regions) upon blue light excitation. A purposely designed numerical approach enables evaluating how the spectroscopic properties of such CDs can be profitable for application in WLEDs emulating daylight characteristics. Subsequently, we fabricate nanocomposite coatings based on the dual color-emitting CDs via solution-based strategies, and we compare their color-converting properties with those of the simulated ones to finally accomplish white light emission. The combined numerical and experimental approach can find a general use to reduce the number of experimental trial-and-error steps required for optimization of CD optical properties for lighting application
A combined size sorting strategy for monodisperse plasmonic nanostructures
No full textThe fabrication of highly monodisperse silica coated Au NPs by the microemulsion approach and the selection of the nanostructure morphology have been described. Several experimental conditions, synthetic parameters and post-preparative strategies such as reaction time, precursor concentration, size selection techniques and NP surface treatments have been suitably investigated in order to fabricate Au and Au@SiO2 NPs with peculiar and tuneable plasmonic properties that strongly depend on the specific size distribution and nanostructure morphology. In particular, size selected precipitation of oleylaminecapped Au NPs by antisolvent titration has successfully offered a strategy to discriminate and collect monodisperse fractions with different average size and narrow size distribution. Moreover, for the first time, a deep insight into the microemulsion mechanism for the silica shell growth has been provided, highlighting the critical role played by the density of oleylamine at the Au NP surface. Specifically the capping agent has been demonstrated to strongly determine the multiplicity of the core in the final Au@SiO2 nanostructures. Density gradient centrifugation has been finally performed to sort the achieved Au@SiO2 NPs with different morphologies, which was ultimately able to recover a significant fraction formed of two Au NPs in one silica shell. A systematic characterization of the Au and Au@SiO2 NPs has been carried out by complementary morphological and spectroscopic techniques. These deeply investigated materials, with tuneable plasmonic properties, have been proposed as versatile building blocks useful for the design and fabrication of plasmonic and photonic structures as well as metamaterials for device applications
Electroactive Layer-by-Layer Plasmonic Architectures Based on Au Nanorods
No full textNanostructured films based on Au nanorods (NRs) have been obtained by layer-by-layer (LbL) assembly driven by electrostatic interaction between metal nanoparticles and polyelectrolytes. Multilayer films have been fabricated by using LbL assembly of poly(sodium styrenesulfonate) (PSS) and positively charged Au NRs on a polyelectrolyte-modified substrate. The effect of fabrication parameters, including the nature of the substrate, the polyelectrolyte initial anchoring layer, and the number of layers has been investigated by means of UV vis absorbance spectroscopy and atomic force microscopy (AFM). The results demonstrated the dependence of morphology and plasmonic features in the multilayered nanostructured architectures from the nature of the anchoring polyelectrolyte on the substrate, the number of layers, and the kind of NR mutual assembly. In addition, a study of the electrochemical activity at the solid/liquid interface has been carried out in order to assess charge transport through the NR multilayer by using two molecular probes in solution, namely, potassium ferricyanide, a common and well-established redox mediator with reversible behavior, and cytochrome C, a robust model redox protein. The presented systematic study of the immobilization of Au NRs opens the venue to several application areas, such as (bio)chemical sensing
Role of Metal Nanoparticles in TiO2/Ag Nanocomposite-Based Microheterogeneous Photocatalysis
No full textThe photocatalytic performance of anatase TiO2 nanorod-stabilized Ag nanoparticles has been investigated during the reductive bleaching of a model dye, Uniblue A (UBA), in homogeneous organic solutions. The activity of the TiO2/Ag nanocomposite has been found to vary continuously during the course of photocatalysis, following a concomitant light-induced modification of the metal nanoparticle size and size distribution. The direct involvement of the metal particles in mediating electron transfer between photoexcited TiO2 and the target UBA is explained on the basis of the size-dependent redox properties of the metal nanoparticles. The present results can be useful in the design of new composite materials with well-tailored photocatalytic properties and long-term stability
Exploring Carbon Dots: Green Nanomaterials for Unconventional Lasing
No full textIn recent years, the progress toward lighting miniaturization is focused on luminescent nanomaterials. Among them, fluorescent carbon dots (CDs) are receiving increasing attention thanks to their astonishing optical properties complemented by their intrinsic biocompatibility and low toxicity. The CDs can be easily dispersed in water, organic solvents or incorporated in polymeric matrices, preserving their emission properties. However, the relationship between their structural and optical properties is still not fully elucidated, motivating a consistent research effort for the comprehension of their features. Nevertheless, CDs demonstrate to be efficient gain materials for lasing, thanks to their high quantum yield (QY), emission tunability in the visible and near infrared (NIR) range, short lifetimes, and high absorption cross section, even if the synthetic reproducibility, the low reaction yield and the spectral width of the emission may limit their effective exploitation. This review summarizes the latest advancements in the investigation of the characteristic properties of CDs that make laser action possible, illustrating optical geometries for lasing and random lasing, both in solution and solid state, and the few currently demonstrated breakthroughs. While the journey toward their effective application is still long, the potential of CD-based laser sources is promising in various technological fields and futuristic perspectives will be discussed
UV-induced photocatalytic degradation of azo dyes by organic-capped ZnO nanocrystals immobilized onto substrates RID C-5449-2009 RID C-5360-2009
No full textZnO nanocrystals (mean particle size: 6 nm) with different surface organic coating and commercial ZnO powder (mean particle size: 200 nm) have been immobilized onto transparent substrates and comparatively examined as photocatalysts for the UV-induced degradation of two azo dyes, Methyl Red and Methyl Orange, in water. The effects of the pH, of the catalyst surface status, and of the dye chemical structure on the course of the photocatalysis are discussed. Reasonable degradation pathways for both target molecules are proposed on the basis of the structural identification of several by-products. The results demonstrate that surfactant-capped ZnO nanocrystals exhibit more versatile performances than those of conventional ZnO-based photocatalysts, because the surface organic coating makes the oxide resistant to photocorrosion and to pH changes. Surface-protected ZnO nanocrystals can be regarded as a valuable alternative to standard TiO(2) photocatalysts. (c) 2005 Elsevier B.V. All rights reserved
Patterned assembly of luminescent nanocrystals: Role of the molecular chemistry at the interface
No full textA simple fabrication approach for achieving nanoparticle patterns based on a room temperature chemically driven strategy is reported. Suitably engineered colloidal luminescent nanocrystals (NCs) (4 and 6 nm in diameter), namely organic capped and silica-coated negatively charged CdSe@ZnS NCs, have been selectively assembled onto defined domains in a binary hydrophobic/hydrophilic chemical pattern, purposely fabricated by combining microcontact printing and wet chemistry procedures. The goal of the work has been to investigate the experimental parameters governing the assembly process at molecular level, in order to elucidate factors regulating interactions at the interfaces. For this purpose, specific sets of conditions, namely substrate patterns and NCs with distinct surface functionalization, have been prepared and tested using different NC dispersing solvents. The NC assembly has been demonstrated driven by non-covalent forces, namely Van der Waals or electrostatic interactions occurring at the NC/substrate interface. The overall study has provided a comprehensive understanding of the role of solvent and molecular chemistry at interfaces in NC assembling. The obtained results can be valuable to set up reliable procedures for developing reproducible patterning protocols potentially useful for the fabrication of NC-based devices. © 2014 Springer Science+Business Media
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