LMNT Research Highlights



Design of Carbon Dots Photoluminescence through Organo-Functional Silane Grafting for Solid-State Emitting Devices

Advanced optical applications of fluorescent carbon dots (C-dots) require highly integrated host-guest solid-state materials with a careful design of C-dots-matrix interface to control the optical response. We have developed a new synthesis based on the grafting of an organo-functional silane (3-glycidyloxypropyltrimethoxysilane, GPTMS) on amino-functionalized C-dots, which enables the fabrication of highly fluorescent organosilica-based hybrid organic-inorganic films through sol-gel process. The GPTMS grafting onto C-dots has been achieved via an epoxy–amine reaction under controlled conditions. Besides providing an efficient strategy to embed C-dots into a hybrid solid-state material, the modification of C-dots surface by GPTMS allows tuning their photoluminescence properties and gives rise to an additional, intense emission around 490 nm. Photoluminescence spectra reveal an interaction between C-dots surface and the polymeric chains which are locally formed by GPTMS polymerization. The present method is a step forward to the development of a surface modification technology aimed at controlling C-dots host-guest systems at the nanoscale (Scientific Reports 2017, 7, 5469). OPEN ACCESS




Improving the Selective Efficiency of Graphene-Mediated Enhanced Raman Scattering through Molecular Imprinting

Enhancement of Raman scattering signal through graphene is an important property that could be exploited for producing innovative sensing devices with advanced properties. Because the enhancement of Raman scattering is due to only a chemical mechanism, the amplification of the signal is lower than that one produced by excitation of localized surface plasmons. The combination of a highly selective technique, which is molecular imprinting, with graphene-mediated enhanced Raman scattering, represents a new synergistic approach that we have developed in the present work. The careful material design has allowed obtaining a porous composite embedding exfoliated graphene and molecular cavities specifically designed for recognizing Rhodamine 6G. The molecularly imprinted porous samples have shown a signal enhancement that increases as a function of the number of molecular cavities, which are also accountable for the molecular recognition properties. The most efficient sample has shown a Raman enhancement per cavity that exceeds the value of 10^12 and a remarkable molecular selectivity allowing for a Rhodamine 6G signal amplification 4.5 higher than structural analogues such as Rhodamine B and methylene blue. The robust and flexible matrix ensures a good recyclability of the samples without lack of linear response. These results prove the great potential of molecular imprinting as a general strategy to provide selectivity to GERS-active substrates for a new generation of sensing devices (ACS Applied Materials & Interfaces 2016, 8, 34098-34107).




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).





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).






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.



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 18 September 2017

LMNT Laboratorio di Scienza dei Materiali e NanoTecnologie D.A.D.U. - Università di Sassari. Palazzo Pou Salit, Piazza Duomo, 6 - 07041 Alghero (SS)

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