Thermoporometry, a useful tool in a wide range of applications

摘要

Thermoporometry is a calonmetnc method to analyze size and morphology of nanometer-size pores The method is based on pore size dependent melting or freezing of liquids inside the pores In our research, we have expanded the use of the method and obtained new insights about materials in very different applications In the presentation we show how thermoporometry 1° was utilized as a unique tool in determining the distribution of catalytic metal oxide particles in a mesoporous support, 2° was used to understand how the drug materials are deposited in mesoporous drug carriers, vital m understanding of the drug dissolution process, and 3° was employed to determine mesopores structure of cartilage, currently poorly known 1° Freezing of water inside SBA-15 with varying amount (0-9 wt-%) of vanadium oxide (VO) catalyst was measured with DSC The freezing had a three distinct features that were dependent on the VO content These features are seen as peaks in the pore size distribution 1) The first peak at small pore sizes represents the pores separated from the external surface by narrow < 4 5 nm necks, n) The second peak represents water that is separated from the surface by necks with diameters between 4 5 nm and 7 nm, and in) The third peak represents the water located between the pore openings and the necks in the pore structure Because the necks are caused by the VO particles the data gives useful information about the distribution and sizes of the VO particles in the structure 2° When poorly soluble drug celecoxib was loaded into mesoporous silicon drug carrier (PSi), the drug remained in an amorphous state as long as the loaded amount corresponded to a molecular monolayer When more than a monolayer of the drug was loaded, it begun to form crystals The melting temperature of the crystals was observed and it was found that the drug may either crystallize as small crystals on the pore surfaces or as large crystals that occupy the whole cross section of the pore The latter case is unfavorable because the large crystals restrict the diffusion of drug molecule during dissolution Furthermore, it was found that larger drug crystals formed during the dissolution process in 27 nm pores but not in 50 nm pores 3℃artilage consists of 65-80 % of water and its mesoporous structure is not well known because it is difficult to determine with conventional methods However, according to preliminary results it was possible to measure the pore size distribution of mesopores in a bovine cartilage by measuring the melting of water inside the pores The pore size distribution in cartilage was wide, as expected, and had a maximum at ca 8 nm