LMNT Research Highlights



C-dots in ZnO macroporous films with controlled photoluminescence through defects engineering

Graphene Carbon-dots (C-dots) nanocomposites represent a new frontier for highly efficient light-emitting materials with tunable colors in a wide range of the visible spectral region. We have developed a C-dots–ZnO system whose emission is finely controlled through material processing. The C-dots, besides being fluorophores, become a tool for modulating the defects in a ZnO matrix through chemical interactions. Macroporous ZnO films have been prepared via a hard templating route using mesoporous silica spheres which allows full crystallization of the ZnO framework and post-impregnation of large amounts of C-dots within the porous matrix. The photoluminescence spectra are given by a combination of different contributions: C-dots, UV near-band and defects-related ZnO emissions. The reducing action of C-dots in ZnO porous matrix allows engineering the defect-related ZnO emissions. The chromaticity of the nanocomposite, from orange to purple and white, is controlled by adjusting the amounts of C-dots through post-impregnation. (RSC Advances 2016, 6, 55393-55400).






BOOK: The Sol to Gel Transition by Plinio Innocenzi

Sol-Gel chemistry roots are quite ancient but Sol-Gel really appears as a self-standing field of science and technology in the late 70’s. In 1981, the first international conference was held in Padova chaired by late Professor Gottardi and the International Sol-Gel society was launched in 2003. Now Sol-Gel is widely recognized as an important field of science and is spreading far beyond the initial circle of materials chemists. This success of Sol-Gel chemistry exemplified by the development of the field of Hybrid materials, is linking communities together, from physics to biology, from polymers to biomaterials and many others. Some 40 years after the birth of Sol-Gel science, this book is proposing to look back at some basics of the field in a very timely manner. It is always nice from time to time to go back to more fundamental issues since as mentioned by the author “the current trend in materials science is more focusing on applications and fewer studies are devoted to understanding the basic science behind “. Prof. Innocenzi (University of Sassari, Italy) is not only a famous and respected scientist in the field but also a fantastic storyteller, this gives this book a peculiar style and multiplies the pleasure of reading. Throughout the six chapters of this book, we travel along the Sol to Gel Transition in a very concise but detailed way for the pleasure and benefit of the readers. No doubt that this book was necessary and will serve to better educate the young scientists entering the field.




Introducing Ti-GERS: Raman Scattering Enhancement in Graphene-Mesoporous Titania Films

Graphene sheets increase the Raman signal through a chemical enhancement mechanism which gives rise to graphene-mediated enhanced Raman scattering (GERS). The low enhancement factor and the surface available for analysis are, however, a limitation on the application of graphene-mediated enhanced Raman scattering (ERS). We have, therefore, developed a new GERS platform, which is based on mesoporous ordered films made of titania anatase containing dispersed sheets of exfoliated graphene. The analytical enhancement factor has revealed that the combination of titania and graphene produces a significant increase in GERS response using Rhodamine 6G as molecular probe. This is a new effect, which we have defined as Ti-GERS (Titania-induced Graphene-mediated ERS) and is attributed to synergic interfacial interactions between graphene sheets and titania at the nanocrystals edges within the nanocomposite. In the future, the Ti-GERS effect is expected to foster a development of better performing Raman based analytical devices avoiding use of expensive noble metals. (J. Phys. Chem. Lett. 2015, 6, 3149-3154).




Energy Transfer Induced by Carbon Quantum Dots in Porous Zinc Oxide Nanocomposite Films

A one-pot approach making use of a zinc oxide sol precursor and carbon quantum dots, together with a partially fluorinated block copolymer as templating agent, has been used to synthesize a porous matrix characterized by interesting energy transfer properties. The resulting nanocomposite films have been characterized by steady-state 3D mapping that has evidenced a complex behavior as a function of the carbon quantum dots concentration. In particular, the luminescence bands of the zinc oxide matrix appear to be modulated by the broad emission of the carbon quantum dots, which depends on their aggregation state. These results can be thus considered as a step further toward the fine-tuning of the luminescence properties provided by zinc oxide-based nanocomposites as a result of a doping effect due to the presence of carbon quantum dots. (J. Phys. Chem. C. 2015, 119, 2837-2843).




Graphene-mediated surface enhanced Raman scattering in silica mesoporous nanocomposite films

Silica mesoporous nanocomposite films containing graphene nanosheets and gold nanoparticles have been prepared via a one-pot synthesis using a dispersion of exfoliated graphene. The composite films have shown Graphene-mediated Surface-Enhanced Raman Scattering (G-SERS). Graphene has been introduced as dispersed bilayer sheets while gold has been thermally reduced in situ to form nanoparticles of around 6 nm which preferentially nucleate on the surface of the graphene nanosheets. The presence of graphene and gold nanoparticles does not interfere with the self-assembly process and silica mesoporous films ordered as 2D hexagonal structures.The material has shown a remarkable analytical enhancement factor using Rhodamine 6G as a Raman probe. (Phys. Chem. Chem. Phys. 2014, OPEN ACCESS DOI: 10.1039/C4CP03582H).



BOOK: Water Droplets to Nanotechnology: A Journey Through Self-Assembly

The ability of nanostructures to organize into complex arrangements leads to unique materials with valuable applications. Self-assembly is therefore a key concept for nanotechnology, but it can be quite a complex and difficult subject to approach. Water Droplets to Nanotechnology gives a simple and general overview of the different self-assembly processes which are at the basis of recent developments in nanotechnology. The book shows how simple phenomenon from everyday examples can become sophisticated tools for self-assembly and the fabrication of nanomaterials. By exploring the coffee stain and tears of wine phenomena, the first part looks at how the evaporation of a droplet of colloidal solution can be used in designing organized structures. This leads onto more complex systems such as templated porous materials, photonic crystals, colloidal nanocrystals and quasi-crystals through to bottom-up systems for designing hierarchal materials. By taking the reader on a journey from everyday life to the secrets of nanotechnology, the book is suitable for a nonspecialist audience interested in self-assembly as well as the wider perspectives and latest developments of nanoscience.







Updated 22 July 2016

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