Thermal behaviour and excess entropy of bioactive glasses and Zn-doped glasses.

International audienceBioactive glasses prepared in SiO2-CaO-Na2O and P2O5 system are used as biomaterials in orthopaedic and maxillofacial surgery. Zn presents high physiological interest. It enhances physiological effects of implanted biomaterials. In this work, the thermal characteristics (Tg, Tc and Tf) of pure bioactive glass elaborated with different amounts of CaO, Na2O in pure glass and with different amounts of introduced Zn in glass (ranging from 0.1 to 10 in wt%), were studied. The excess entropy was calculated for different compounds. Glasses were prepared by the melting process. The thermal behaviour of obtained bioactive glasses was determined using differential thermal analysis. Therefore, the glass transition (Tg), the crystallization (Tc) and the melting temperatures (Tf) were revealed. Moreover, according to Dietzel formula, the thermal stability (TS) of the studied bioactive glasses has been calculated. The first results concerning the impact of different oxides, revealed a decrease of the TS, Tg, Tc and Tf when the SiO2/CaO increases and revealed an increase of these thermal characteristics when the SiO2/Na2O and CaO/Na2O ratios increase. Introducing Zn into the bioactive glasses induces a decrease of Tf and an increase of TS. Contrary to crystals, prepared glasses have entropy different to zero at T = 0 K and vary versus Tf. The excess entropy of pure glasses and Zn-doped glasses were calculated. The significant variations were registered

Coherent Plasmon-Plasmon and Plasmon-Exciton Interactions at the Nanoscale

Noble metallic nanoparticles which supports localized surface plasmon resonances, offers a variety of potential scientific as well as industrial applications. Due to a remarkable ability to confine light at nanoscale dimensions, far below the optical diffraction limit, together with an ability to detect minute changes in the local environment plasmonic nanoparticles have paved routes towards several new and intriguing techniques, promising for future applications in areas such as molecular sensing and quantum optics.The exploitation of coherent interations at the nanoscale is rather frequent in the scientific community, and has recently resulted in several prominent discoveries, which have ended up as publications in high-ranked scientific journals. However, numerous studies demonstrates utilization of coherent interactions in rather complicated systems, which is often costly and impractical for future development. Plenty of the phenomena presented within these studies are moreover based on measurements on an ensemble level, where there is either no or very limited knowledge in the performance of single nanoparticles. In this thesis we first present and demonstrate ways to acheive ultracompact and competitive molecular analysis in nanosized systems, which supports directional scattering properties due to coherent plasmon-plasmon interactions. Secondly we also demonstrates realization of strong light-matter interactions from plasmon-exciton coupling in nanosized systems comprised by single crystalline Ag nanoprisms and J-aggregated molecular sheets of TDBC. These demonstrations support promising outlooks for future plasmonic molecular analysis as well as room temperature quantum plasmonics and quantum optics

Coherent Plasmon-Plasmon and Plasmon-Exciton Interactions at the Nanoscale

Noble metallic nanoparticles which supports localized surface plasmon resonances, offers a variety of potential scientific as well as industrial applications. Due to a remarkable ability to confine light at nanoscale dimensions, far below the optical diffraction limit, together with an ability to detect minute changes in the local environment plasmonic nanoparticles have paved routes towards several new and intriguing techniques, promising for future applications in areas such as molecular sensing and quantum optics.The exploitation of coherent interations at the nanoscale is rather frequent in the scientific community, and has recently resulted in several prominent discoveries, which have ended up as publications in high-ranked scientific journals. However, numerous studies demonstrates utilization of coherent interactions in rather complicated systems, which is often costly and impractical for future development. Plenty of the phenomena presented within these studies are moreover based on measurements on an ensemble level, where there is either no or very limited knowledge in the performance of single nanoparticles. In this thesis we first present and demonstrate ways to acheive ultracompact and competitive molecular analysis in nanosized systems, which supports directional scattering properties due to coherent plasmon-plasmon interactions. Secondly we also demonstrates realization of strong light-matter interactions from plasmon-exciton coupling in nanosized systems comprised by single crystalline Ag nanoprisms and J-aggregated molecular sheets of TDBC. These demonstrations support promising outlooks for future plasmonic molecular analysis as well as room temperature quantum plasmonics and quantum optics

Strong Light-Matter Interactions and Formation of Hybrid States at the Nanoscale

Noble metallic nanoparticles, which support localized surface plasmon resonances (LSPR), offer a variety of potential scientific and industrial utilizations. Due to their remarkable ability to confine light at nanoscale dimensions, far below the optical diffraction limit, plasmonic nanoparticles enable intricate light manipulations, which may be performed and exploited for a wide range of future revolutionary applications. For instance, LSPR in noble metal nanoparticles may be coupled to and coherently interact with exciton resonances in semiconducting nanocrystals and/or dye molecules. If the coupling strength is strong enough it is possible to create nanoscale systems, which support a new type of hybrid excitations. These excitations cannot be thought of as neither plasmonic nor excitonic, but rather an indistinguishable mixture of both. These type of excitations need to be considered as being half-light/half-matter entities and may be treated as quasiparticles, referred to as polaritons. Such quasiparticles have shown to possess properties, which open up completely new routes toward light manipulation at the nanoscale and have recently attracted tremendous attention and interest within the scientific nano-optics and nano-photonics communities. \ua0The subject of this thesis is to both experimentally and theoretically demonstrate strong light-matter interactions in isolated single particle nanoscale plasmon-exciton systems, as well as discussing possible applications. The systems described and presented in this thesis are composed of single crystalline Ag nanoprisms attached to J-aggregated dye molecules, as well as Ag nanoprisms coupled to excitons in 2D material transition metal dichalcogenides (TMDC) monolayers. The experimental results presented in this thesis support promising outlooks for future plasmonic molecular manipulations as well as room temperature quantum plasmonics and quantum optics

Evaluation of the kinetic and relaxation time of gentamicin sulfate released from hybrid biomaterial Bioglass-chitosan scaffolds

International audienceChitosan scaffolds, combined with bioactive glass 46S6, were prepared to serve as gentamicin sulfate delivery in situ systems for bone biomaterials. This work presents a study about the effect of the ratio chitosan/bioactive glass (CH/BG) on the release of gentamicin sulfate and on the bioactivity during in vitro experiments. SEM observations allowed understanding the bond between the glass grains and the chitosan matrix. In vitro results showed that scaffolds form a hydroxyapatite (HA) Ca10(PO4)6(OH)2 after 15 days of immersion in a simulated body fluid (SBF).The interest of this study is to see that the increase of the content of bioactive glass in the chitosan matrix slows the release of gentamicin sulfate in the liquid medium. Starting concentration of gentamicin sulfate has an influence on the relaxation time of the scaffolds. Indeed, an increasing concentration delays the return to a new equilibrium. Contents of chitosan and bioactive glass do not affect the relaxation time. Synthesized scaffolds could be adapted to a clinical situation: severity and type of infection, weight and age of the patient

Thermal investigations of Ti and Ag-​doped bioactive glasses

International audienceThe purpose of this paper is to explore the effect of titanium and silver on the characteristic temperatures of 46S6 glass and the excess entropy. The results show that the adding of these metals in the chemical composition does not affect the amorphous character of glasses. The introduction of these elements greatly reduces the melting temperatures of glasses and involves similar variations on the crystallization and glass transition temperatures. These elements also increase the thermal stability of glasses. The excess entropy calculations show a decrease when the content of Ti or Ag increases. Contrary to crystals, synthesized glasses have entropy different to zero at T = 0 K

Excess entropy and thermal behavior of Cu- and Ti-doped bioactive glasses

International audienceBioactive glasses belong to the ceramic family. They are good materials for implantation due to their excellent capacities to create an intimate bond with bones. Copper is known for its anti-inflammatory, antibacterial, and antifungal properties. Titanium is biocompatible and resistant to corrosion. These chemical elements can be introduced in bioactive glasses to provide a wide variety of uses and to enhance the physiological properties of implanted biomaterials. In this work, bioactive glasses doped with different contents of copper and titanium were synthesized by the melting method. The purpose is to study the effect of doping metal element on the thermal characteristics (T g, T c, and T f). The results revealed that the increase of the content of copper and titanium in the glass matrix decreases the melting temperature and induces an increase of the thermal stability. The excess entropies of pure and doped glasses were calculated. Obtained results highlighted the decrease of the excess entropy with the increase of metal elements contents

Comparative Study of Nanobioactive Glass Quaternary System 46S6

International audienceDifferent bioactive glass systems have been prepared by sol-gel. However, the production of Na2O-containing bioactive glasses by sol-gel methods has proved to be difficult as the sodium nitrate used in the preparation could be lost from the glass structure during filtration and washing. The aim of this study was to prepare the quaternary system 46S6 of bioactive glass by modified sol-gel techniques with a decrease in the time of gelation. In addition, compare the behaviour of the prepared sol-gel bioactive glass system by its corresponding prepared by melting. The obtained glasses were characterized by using several physicochemical techniques; XRD, FTIR, TEM and SEM beside the effect of the glass particles on the viability of osteoblast like cells (Saos-2). Results show that nanopowders 40-60 nm of 46S6 glass system had been prepared by modified sol-gel (acid-base reaction) method at 600°C in just three days at 600°C. Cell viability by MTT assay confirmed the effectiveness of the prepared nanobioactive glass

Study of bioactive glass ceramic for use as bone biomaterial in vivo: investigation by Nuclear Magnetic Resonance and Histology

International audienceThe performance of the porous glass ceramic doped with 10% wt Zinc and 2% wt TiN (46S6-10Zn),in the restoration of critical diaphyseal bone defect, was evaluated by several physicochemical methods and histological studies. The critical defect in rabbits was created and then filled with 46S6-10Zn. At different periods after implementation, animals were sacrificed. Samples were harvested for exploration. The nuclear magnetic resonance (MAS-NMR) of 31P and 29Si illustrates the progressive degradation of 46S6-10Zn in favor to of the formation and the development of biological apatite. Therefore, after one month of implementation, MAS- NMR 29Si proves the presence of Q2 (25%), Q3 (73%) and Q4 (2%). However, after six months, the disappearance of all these species was revealed and characterized by the 46S6-10Zn dissolution. Besides, MAS- NMR 31P demonstrates the presence of Qc° (4%), QHA° (55%) and Qa° (41%) after one month. Nevertheless, six months later, we observe the presence of QHA° (80%) and Qa° (20%). Histological study demonstrates an intimate contact of 46S6-10Zn surrounding bone after one month of implantation. However, after four months, mature bone matrix became calcified and the implanted 46S6-10Zn began to be degraded. Moreover, nine months later, 46S6-10Zn was nearly resorbed and replaced by a calcified tissue in the periphery and an osteoid tissue in the middle of bone defect

Suppression of photo-oxidation of organic chromophores by strong coupling to plasmonic nanoantennas

Intermixed light-matter quasi-particles—polaritons—have unique optical properties owing to their compositional nature. These intriguing hybrid states have been extensively studied over the past decades in a wide range of realizations aiming at both basic science and emerging applications. However, recently, it has been demonstrated that not only optical but also material-related properties, such as chemical reactivity and charge transport, may be significantly altered in the strong coupling regime of light-matter interactions. We show that a nanoscale system, composed of a plasmonic nanoprism strongly coupled to excitons in a J-aggregated form of organic chromophores, experiences modified excited-state dynamics and, therefore, modified photochemical reactivity. Our experimental results reveal that photobleaching, one of the most fundamental photochemical reactions, can be effectively controlled and suppressed by the degree of plasmon-exciton coupling and detuning. In particular, we observe a 100-fold stabilization of organic dyes for the red-detuned nanoparticles. Our findings contribute to understanding of photochemical properties in the strong coupling regime and may find important implications for the performance and improved stability of optical devices incorporating organic dyes