Probing sol-gel matrices microenvironments by PGSE HR-MAS NMR

Area of Science:

• Materials Science
• Physical Chemistry
• Biocatalysis

Background:

• Sol-gel matrices are crucial for enzyme encapsulation in biocatalysis.
• Understanding the microenvironment within these matrices is key to optimizing enzyme activity.

Purpose of the Study:

• To investigate the local chemical microenvironment of sol-gel matrices (TMOS/MTMS and TMOS/BTMS) used for enzyme encapsulation.
• To study the transport properties of solvents with varying polarities within these matrices.

Main Methods:

• Pulsed Gradient Spin Echo diffusion with high-resolution magic angle spinning Nuclear Magnetic Resonance (NMR).
• Analysis of solvent self-diffusion coefficients and root mean square displacements.
• Application of the Kärger model for fitting data.

Main Results:

• Two distinct diffusion domains (fast and slow) were observed for solvents within the sol-gel matrices.
• The fast diffusion domain exhibited free diffusion, while the slow domain's regime depended on the matrix.
• Solvent exchange dynamics varied: n-hexane showed intermediate exchange, polar solvents showed slow exchange in TMOS/BTMS and intermediate in TMOS/MTMS.

Conclusions:

• Sol-gel pores are predominantly hydrophobic, but hydrophilic groups influence polar solvent exchange.
• The observed solvent dynamics and microenvironment characteristics are relevant for understanding enzyme activity in these biocatalytic materials.