Chemical tuning of Coulomb blockade at room-temperature in ultra-small platinum nanoparticle self-assemblies

This work describes self-assemblies of ultra-small platinum nanoparticles, the electrical properties of which can be adjusted through slight modifications of the assemblies' constituents. Elaborating such systems, stable in air for months, is a first step towards nanoelectronic systems, where the charging energy of the nanoparticles is tuned by the nature of the ligands

The role of natural products and their multitargeted approach to treat solid cancer

Natural products play a critical role in the discovery and development of numerous drugs for the treatment of various types of cancer. These phytochemicals have demonstrated anti-carcinogenic properties by interfering with the initiation, development, and progression of cancer through altering various mechanisms such as cellular proliferation, differentiation, apoptosis, angiogenesis, and metastasis. Treating multifactorial diseases, such as cancer with agents targeting a single target, might lead to limited success and, in many cases, unsatisfactory outcomes. Various epidemiological studies have shown that the steady consumption of fruits and vegetables is intensely associated with a reduced risk of cancer. Since ancient period, plants, herbs, and other natural products have been used as healing agents. Likewise, most of the medicinal ingredients accessible today are originated from the natural resources. Regardless of achievements, developing bioactive compounds and drugs from natural products has remained challenging, in part because of the problem associated with large-scale sequestration and mechanistic understanding. With significant progress in the landscape of cancer therapy and the rising use of cutting-edge technologies, we may have come to a crossroads to review approaches to identify the potential natural products and investigate their therapeutic efficacy. In the present review, we summarize the recent developments in natural products-based cancer research and its application in generating novel systemic strategies with a focus on underlying molecular mechanisms in solid cancer

Spin crossover in Fe(triazole)–Pt nanoparticle self-assembly structured at the sub-5 nm scale

A main goal of molecular electronics is to relate the performance of devices to the structure and electronic state of molecules. Among the variety of possibilities that organic, organometallic and coordination chemistries offer to tune the energy levels of molecular components, spin crossover phenomenon is a perfect candidate for elaboration of molecular switches. The reorganization of the electronic state population of the molecules associated to the spin crossover can indeed lead to a significant change in conductivity. However, molecular spin crossover is very sensitive to the environment and can disappear once the molecules are integrated into devices. Here, we show that the association of ultra-small 1.2 nm platinum nanoparticles with FeII triazole-based spin crossover coordination polymers leads to self-assemblies, extremely well organized at the sub-3 nm scale. The quasi-perfect alignment of nanoparticles observed by transmission electron microscopy, in addition to specific signature in infrared spectroscopy, demonstrates the coordination of the long-chain molecules with the nanoparticles. Spin crossover is confirmed in such assemblies by X-ray absorption spectroscopic measurements and shows unambiguous characteristics both in magnetic and charge transport measurements. Coordinating polymers are therefore ideal candidates for the elaboration of robust, well-organized, hybrid self-assemblies with metallic nanoparticles, while maintaining sensitive functional properties, such as spin crossover

Transport de charge dans les assemblages de nanostructures magnétiques, non magnétiques et à spin cross-over complexes

Understanding charge transport properties of metallic and magnetic nano-structures is highly important for the development and miniaturization of modern functional devices. In particular, chemically synthesized nano-structures are in focus as they provide better control over their shape and size, which can be used to tune their charge transport properties. The aim of this thesis is to study the various aspects of charge transport properties which emerge due to the small size and magnetic nature of different types of nanostructures which include Pt nanoparticles (1.3-3 nm), FeCo magnetic particles (⁓10 nm), and Fe (II) triazole based coordination complex. To further specify, phenomenon such as Coulomb blockade, tunnel magnetoresistance and spin-transition will be in focus. Depending on the desirable property, these nanostructures can be exploited for their applications in a variety of sensors, actuators and spintronic devices etc.La compréhension des propriétés de transport de charge des nanostructures métalliques et magnétiques est très importante pour le développement et la miniaturisation des dispositifs fonctionnels modernes. En particulier, les nanostructures synthétisées chimiquement sont intéressant car elles permettent de mieux contrôler leur forme et leur taille, ce qui peut être utilisé pour ajuster leurs propriétés de transport de charge. L'objectif de cette thèse est d'étudier les aspects différents des propriétés de transport de charge qui résultent de la petite taille et de la nature magnétique de différents types de nanostructures comprenant des nanoparticules de Pt (1,3-3 nm), des particules magnétiques FeCo (⁓10 nm), et complexe de coordination à base de triazole Fe (II). Pour préciser davantage, des phénomènes tels que le blocage de Coulomb, la magnétorésistance tunnel et la transition de spin seront mis en évidence. En fonction de la propriété souhaitée, ces nanostructures peuvent être exploitées pour leurs applications dans divers capteurs, actionneurs et dispositifs spintroniques, etc

A quantum chemistry background of sickle cell anemia and gaps in antisickling drug development

Sickle cell anemia disease has been a great challenge for the world in the present situation. It occurs only due to the polymerization of sickle hemoglobin (HbS) having Pro-Val-Glu (PVG) typed mutation, while the polymerization does not occur in normal hemoglobin (HbA) having Pro-Glu-Glu (PGG) residues. According to data from the literature, Val-beta6 of Pro-Val-Glu is hydrophobic in nature, which appears to fit into a hydrophobic pocket in the adjacent HbS. After the insertion of Pro-Val-Glu into a hydrophobic pocket on the adjacent HbS, the polymerization is started. This is a questionable point on how the replacement of glutamic acid with valine in HbS makes it more reactive to fit into a hydrophobic pocket on adjacent HbS for polymerization. No data from the literature on the reactivity of HbS for polymerization was found yet. This is the first time that the theoretical calculation was done in both HbA and HbS where they were structurally different. After that, a comparative study between PVG and PGG was done at quantum level for the evaluation of the reactivity to fit into a hydrophobic pocket on adjacent HbS. At a quantum level, it was found that the HOMO-LUMO gap of Pro-Val-Glu was lower than that of Pro-Glu-Glu. According to the data from the literature, the lesser HOMO-LUMO gap promotes the initiation of the polymerization reaction. On the basis of the results, it was also shown how the mutation point (Pro-Val-Glu) in HbS becomes more reactive to polymerization, whereas Pro-Glu-Glu in HbA does not. The computational method developed for the first time will be very helpful not only for molecular biologists but also for computational and medicinal chemists. Additionally, the required modifications based on gaps in anti-sickling drug development are also suggested in the presented article

Study on Adiponectin Levels in Polycystic Ovary Syndrome Cases

Introduction: Low adiponectin levels in polycystic ovarian syndrome (PCOS) have been largely attributed to obesity which is common among these patients. In addition, evidence also suggests that low adiponectin in PCOS may be related to insulin resistance (IR) in these women. However, studies on the role of adiponectin in younger and lean patients are limited. Therefore, the aim of the present study was to examine the association of adiponectin levels in young and lean women with PCOS.Methodology: This case control study included 75 participants for each.75 women for cases were included who had PCOS. This study was carried in Department of Biochemistry & Department of Obs/Gynae in Patna Medical College, Patna, Bihar. The duration of study was over a period of two years.Results: The result of this study revealed that adiponectin level <13.0 in 27 PCOS cases and in 45 healthy participants, rest were having >13.0 adiponectin level. Conclusion: This study concludes that the serum adiponectin levels can be used as a potential independent biomarker for diagnosis of PCOS

Tunnel magnetoresistance and cotunneling in assemblies of chemically synthesized FeCo nanoparticles

International audienceMagnetotransport studies in assemblies of chemically synthesized FeCo nanoparticles have been performed between 1.8 and 300 K. The samples display tunnel magnetoresistance (TMR), the amplitude of which ranges between 3 and 11% at low temperature, and could persist up to 0.5% at room temperature. A quantitative analysis of the resistance-temperature and current-voltage characteristics evidences the presence of cotunneling effect inside the samples, which becomes the dominant transport mechanism below 40 K. The presence of cotunneling at low temperature is clearly correlated with an increase of TMR amplitude. Interestingly, in some samples, the TMR amplitude increases with voltage, a phenomenon which is shown to be correlated with an increase of the number of junctions involved in the tunneling process. Extent of cotunneling and TMR amplitude was found to be higher in case of samples prepared by drop casting compared to those prepared by dielectrophoresis. In the former case, the assemblies are more ramified than in the latter case, indicating the importance of controlling the structural properties, and especially the mean number of neighbors of an assembly, in order to observe the cotunneling enhancement of the TMR amplitude. Apart from TMR, two other types of magnetoresistance occurring at larger magnetic field were measured. One of them could reach up to 16% in certain cases. The cotunneling enhancement of TMR amplitude in chemically synthesized nanoparticles could be used to improve response of cheap magnetic sensors elaborated using on-chip deposition of colloidal solution of magnetic nanoparticles

Tuning Coulomb blockade in ultra-small metallic nanoparticle self-assemblies, at room-temperature

International audienceTuning Coulomb blockade at room temperature in nanoparticle self-assemblies can open the door to the development of a new class of nanoelectronics. Here, we describe self-assemblies of ultrasmall platinum nanoparticles, the morphology and electrical properties of which can be tuned through slight modifications of their aryl- or alkyl thiol ligand backbones or chain length. Three parameters have been modified independently at an unprecedented fine level to control the Coulomb blockade energy: the size of the nanoparticles (between 1.2 and 1.7 nm), the distance between them (between 1.9 and 2.5 nm) and the dielectric constant of the ligands (between 2.7 and 7.1). Elaborating such systems, stable in air for months, and understanding their electrical properties are first steps towards nanoelectronic systems where the charging energy of the nanoparticles can be tuned by the nature of the ligands

Tuning Coulomb blockade in ultra-small metallic nanoparticle self-assemblies, at room-temperature

International audienceTuning Coulomb blockade at room temperature in nanoparticle self-assemblies can open the door to the development of a new class of nanoelectronics. Here, we describe self-assemblies of ultrasmall platinum nanoparticles, the morphology and electrical properties of which can be tuned through slight modifications of their aryl- or alkyl thiol ligand backbones or chain length. Three parameters have been modified independently at an unprecedented fine level to control the Coulomb blockade energy: the size of the nanoparticles (between 1.2 and 1.7 nm), the distance between them (between 1.9 and 2.5 nm) and the dielectric constant of the ligands (between 2.7 and 7.1). Elaborating such systems, stable in air for months, and understanding their electrical properties are first steps towards nanoelectronic systems where the charging energy of the nanoparticles can be tuned by the nature of the ligands

Influence of the pore diameter in Cu/Co/Cu antidots: A XANES study

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