Fabrication, functionalization and characterization of silica monolith for forensic chemistry applications

Khattab, Amin Khalid

Abstract

The physiochemical properties of silica monolith make it an ideal base material for drugs extracting, pre-concentrating and separation from biological samples which can interact not only with molecules but also with ions and atoms. However, the fabrication of silica monoliths still has some problems, such as cost, limited capacity and fabrication and modification methodology, which can be time consuming and labour intensive. Structure evolution of silica monolith was studied in microwave and conventionally processed samples over the temperature range from 25 to 70 oC. The samples were produced using sol-gel processing. The microwave process was performed using a single mode cavity at 2.45GHz. Characterization of produced silica monoliths were carried out using a variety of techniques, including Scanning Electron Microscopy (SEM) analysis, EDX analysis, BET and BJH analysis. The data obtained showed that structural differences do exist between conventional and microwave processed samples. It was found however, that microwave based fabrication offered a significantly quicker (11 min) gelation process, compared to those obtained using the thermal heated oven methodology (4,320 min).

The silica monolithic surfaces were modified with three different phases C₁₈, gold nanoparticles and graphene which received a thermal treatment at different programmed powers in two different ovens, conventional and microwave. Three substantial variance were also identified from the structural characterization of modified silica surfaces processed using microwave heating and conventional heating methods:

1- The use of microwave heating during C₁₈ surface modification improved not only the attachment of C₁₈ groups to the silica surface but also increased the extraction efficiency of caffeine and eserine from standard solutions (102 % and 97 %, respectively).

2- The fabrication of gold nanoparticles-NH2-silica monolith using microwave heating was found to improve the sensitivity and selectivity of modified silica surface and make possible to extract, detect and quantify more than one type of drugs of abuse at the same time within few minutes.

3- Using graphene-silica monolith makes the extraction of non-polar, polar, very polar and water-soluble analytes, based on both hydrophobic and electronic interactions, easy and simple.

Fabrication and modification of silica monoliths using microwave heating make the sol-gel procedure much faster and easier and allow for non-polar, polar, very polar and water-soluble analytes to be extracted more efficiently to produce accurate and precise results compared to the conventional method for fabrication and modification of silica monoliths using three phases (C₁₈, gold nanoparticles and graphene).

Finally, this technique make the modified silica monolithic column capable to extract selected drugs of abuse from biological samples and produce qualitative and quantitative results at the same time using chemiluminescence based immunoassays or HPLC-UV.

Citation

Khattab, A. K. (2014). Fabrication, functionalization and characterization of silica monolith for forensic chemistry applications. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4216084

• Thesis Type: Thesis
• Deposit Date: Dec 4, 2014
• Publicly Available Date: Feb 23, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4216084
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: May 1, 2014