Size-Dependent Melting Behavior of Colloidal In, Sn and Bi Nanocrystals

Abstract

Colloidal nanocrystals are a technologically important class of nanostructures whose phase change properties have been largely unexplored. Here we report on the melting behavior of In, Sn, and Bi nanocrystals dispersed in a polymer matrix. This polymer matrix prevents the nanocrystals from coalescing with one another and enables previously unaccessed observations on the melting behavior of colloidal nanocrystals. We measure the melting temperature, melting enthalpy, and melting entropy of colloidal nanocrystals with diameters of approximately 10 to 20 nm. All of these properties decrease as nanocrystal size decreases, although the depression rate for melting temperature is comparatively slower than that of melting enthalpy and melting entropy. We also observe an elevated melting temperature during the initial melt-freeze cycle that we attribute to surface stabilization from the organic ligands on the nanocrystal surface. Broad endothermic melting valleys and very large supercoolings in our calorimetry data suggest that colloidal nanocrystals exhibit a significant amount of surface pre-melting and low heterogeneous nucleation probabilities during freezing.

Nanofluid based on self-nanoencapsulated metal/metal alloys phase change materials with tuneable crystallisation temperature

“…In most cases, encapsulation is obtained by inserting nanoparticles into a high melting temperature matrix 11 – 17 , or by growing a silica 18 – 23 or trioctyl phosphine oxide TOPO 24 shell around them. Different metal cores have been investigated: indium 11 , 16 , 18 , 19 , bismuth 11 – 13 , 16 , 17 , tin 11 , 16 , 20 – 23 , cadmium 11 , lead 11 , 15 , zinc 24 , and their alloys 14 , 17 , 25 . Generally speaking, if metal cores are lower than 50 nm, lowering melting temperature and melting and crystallisation enthalpy values than those measured in the bulk material are observed due to the substantial contribution of the metal atoms near the shell 26 , 27 .…”

Optimization of nimesulide-loaded solid lipid nanoparticles (SLN) by factorial design, release profile and cytotoxicity in human Colon adenocarcinoma cell line

“…The melting behaviour of triacylglycerols nanoparticles strongly depends on particle size, irrespective of matrix material and stabilizer composition. From thermodynamics, it is expected that the melting temperature of colloidal substances would decrease with the decrease of the particle size[24]. Models based on the Thompson equation modified for crystalline materials, or the well-known Gibbs-Thompson equation, are often used to describe the particle size dependence of the melting temperature.They are described using the following equation:…”

Bi2(C2O4)3·7H2O and Bi(C2O4)OH Oxalates Thermal Decomposition Revisited. Formation of Nanoparticles with a Lower Melting Point than Bulk Bismuth

“…Solid line: calculated from Equation 1; black dashed line: bulk melting point. mer 57 ) have been reported. The matrices allow to prevent nanoparticle coalescence and to repeat melting measurements.…”