In this study, we have investigated a behavior of particle with diameter several ten nanometers size at the time of heating on an atomic scale by numerical analysis using the molecular dynamics (MD) simulation. On solving the equation of motion, the Langevin equation was adopted. The Finnis-Sinclair potential, which can well reproduce the mechanical properties of a BCC-metal, was used as the interatomic force. We determined the relationship between the melting point (Tm) of the nano-sized particles and its diameter by MD simulations. We have also investigated the self-diffusion coefficient of each atom-forming at a temperature larger or less than Tm of the submicron-size metal particles . As a result, even in case of heating at a temperature larger than Tm, the mean self-diffusion coefficient at the center of a particle was 10-7–10-6 cm2/sec. On the other hand, at the surface layer of the particle was two to three orders of magnitude larger than that at the center. Those particles were in a quasi-molten state. It is conceivable that the thickness of the surface layer can explain a phenomenon that sintering progresses as the heating temperature increases.

One of the major concerns regarding the clinical translation of metal nanoparticles is related to the question of their persistence in organisms that can increase the likelihood of toxicity and the interaction/interference with common medical diagnoses.

In order to overcome these issues we have recently introduced a versatile 90 nm nano-architecture composed by: i) arrays of 3 nm gold nanoparticles, ii) functionalizable commercial polymers surrounding the gold nanoparticles, and iii) biodegradable and derivatizable silica shell embedding the polymer-nanoparticle assembly. These robust nanocapsules maintain the intriguing features of gold nanospheres but are biodegraded in physiological media to their potentially renal clearable building blocks.

We report preparation and characterization of colloidal gold nanorods (AuNR) with plasmon absorbance over 950 nm and an aspect ratio of 7.2 by tuning silver nitrate concentration and the CTAB/BDAC ratio during growth. Samples were analyzed by scanning transmission electron microscopy, X-ray diffraction, UV-vis absorption spectroscopy and measurement of zeta potential. Addition of 170 μM silver nitrate to the CTAB-containing reaction mixture allowed preparation of AuNRs with a maximum absorbance peak at 941.8 nm and a yield around 96%. Optimization of the BDAC/CTAB ratio allowed for a further redshift of the absorbance maximum to 954.0 nm, but with poorer yields.

Two-Dimensional materials open up great prospects in photodetector applications owing to their sharp optical properties and the ability to combine them in layered heterostructures. Among this new class of materials, colloidal nanoplatelets (NPL) made of cadmium chalcogenides readily combine the thickness control at the atomic level together with the large scale production and ease of processing of colloidal materials. As a strategy to overcome the limited mobility inherent to nanocrystal based devices, the photocarrier lifetime is increased by building an electrolyte-gated phototransistor to passivate the electron traps. NPL can also be coupled with a graphene transport layer collecting the photogenerated charges, thus bypassing the transport bottleneck. We show that the charge transfer is driven by the large exciton binding energy of the NPL, which can be engineered by heterostructured NPL. This allows us to control the magnitude and the direction of the charge transfer to graphene. Eventually, we use nanotrench electrodes to decrease the transit time of the carriers, suppress the influence of film defects and provide an electric field large enough to overcome the large exciton binding energy of NPL.

Copper Indium Sulfide (CIS)-based quantum dots (QDs) are considered as a safer alternative compared to carcinogenic cadmium- and lead-based QDs. Here, we present a facile, high throughput, and non-injection method of synthesizing CIS-based QDs. The structure, shape, size, and crystalline structure of the synthesized QDs were studied using high resolution transmission electron microscopy (HRTEM). The effects of temperature and compositional dependency on the structure and optical properties of the resulting QDs were investigated using elemental, absorption, photoluminescence (PL), and time-resolved spectroscopic analyses. We observed that a gradient increase of temperature during the core growth, as well as addition of excess indium (In) and zinc (Zn) precursors during core and core/shell synthesis, at low growth temperatures, resulted in QDs with improved PL and lifetime. The large Stokes shift, broad emission spectra, and long-lived emission of the synthesized QDs reveal their potential applicability to third generation photovoltaic and optoelectronic devices.

2D materials have shown to be the next step in semiconductor use and device manufacturing that can allow us to reduce the size of most electronics. One of the novel ways to obtain 2D materials is through liquid exfoliation, in which these materials can be obtained by dispersing the smallest possible particles in different solvents. Once obtained, the solutions can be used to manufacture devices via different processes, one of which is inkjet printing. This process relies in selecting “jettable” fluids, which need to have the necessary combination of viscosity and surface energy or “wettability”. In this work we have modified the viscosities and surface energies of five solvents: IPA (Isopropanol), NMP (N-methyl – 2 pyrrolidone), DMA (Dimethylacetamide), DMF (Dimethylformamide) and a mixture of Cyclohexanone / Terpineol 7:3. We have found an avenue to tailor the viscosity of these solvents though the addition of Ethyl Cellulose (EC), where the viscosity has been increased by up to 15 times at an EC concentration of 6%. For inkjet printing, ideally a viscosity of 4 – 10 cP is recommended, which we have been able to achieve with all of the solvents studied. It has been found that the different solvents present different susceptibilities to the EC addition, with DMA and DMF being the least sensitive to the EC addition. We have also studied the change in the drop dynamics and interactions of the 2D solutions with the substrate. Through this analysis we have found solvents that appear to be attractive for inkjet printing of MoS2 and graphite.

Water-stable CdSTe quantum dots were synthesized under microwave irradiation heating conditions. An aqueous telluride solution (produced by reducing metallic Te with NaBH4), cadmium sulphate and thioglycolic acid were mixed together in an oxygen-free atmosphere to prevent oxidation of the telluride species. The reaction temperature varied from 60° C to 180° C and was controlled by using a microwave reactor (1,000 W) to control nucleation rate and tune the size of the quantum dots. Photoluminescence analyses of resulting quantum dots evidenced a red shift (from 490 nm to 640 nm, using an excitation wavelength of 380 nm) when the reaction temperature was increased, which suggested crystal growth. The variation in size was also evidenced by the color of the quantum dot suspensions that changed from blue to red, when excited with a 405 nm, 5mW diode laser. The highest quantum yield was observed for quantum dots synthesized from 120° to 150° C. X-ray diffraction analyses suggested the formation of a solid solution of CdSTe with average crystallite size ranging from 1.4 nm to 3.2 nm. FT-IR spectroscopy evidenced the presence of residual thioglycolic functional groups onto the crystals surface, whereas HRTEM confirmed the nanometric size of the quantum dots.