## 6 Nano-Particles and Nano-Structures
### Gold Nano-Particles  
The immobilization of nano-particles has been used to improve the surface area of polymeric monolithic columns [119], to facilitate the addition of a functional group [129; 130], and to provide a substrate to facilitate interchangeable surface chemistry [131]. In addition to the use of gold nano-particles (AuNPs), the methods used in the immobilization procedures vary from latent reactive surface groups, such as those generated by co-polymerization of reactive monomers (e.g., GMA, NAS) [132], and the grafting of functional groups capable of supporting aminated or thiolated groups for immobilization of AuNPs [9; 129; 130; 131]. A method for the preparation of AuNPs was described by [PERSON] _et al_. in the 1970's, in which the concentration of reducing agent controlled the resulting \begin{table}
\begin{tabular}{l l c c c c} \hline \hline \multirow{2}{*}{**Monolith**} & \multirow{2}{*}{**Reaction**} & **Temperature** & \multirow{2}{*}{**Time**} & **Nano-Particle** & \multirow{2}{*}{**Reference**} \\  & & **(C\({}^{\circ}\))** & & & **Type** & \\ \hline \hline \multirow{2}{*}{**Poly(NAS-co-EDMA)**} & Surface generation of allyme group, followed by thiol-yne & RT & N/A & 20 nm Au & [132] \\  & photo-addition of cysteemine for AuNP modification. & & & & \\ \hline \multirow{2}{*}{**Poly(GMA-co-EDMA)**} & Introduction of surface AuNPs by generation of surface & 100 & 30 min & \multirow{2}{*}{40–50 nm Au} & \multirow{2}{*}{[133]} \\  & thiols from surface epoxide groups. Two methods were used: & RT & 2 h & \\  & (i) Hydrogen sulfide, and (ii) Cysteemine. & RT & 20 min & \\ \hline \hline \multirow{2}{*}{**Poly(BuMA-co-EDMA)**} & Preparation of thiolated and aminated surfaces and & & RT & N/A & 20 nm Au & [134] \\  & comparison of immobilization pathways for AuNPs. & & & & \\ \hline \hline \multirow{2}{*}{**Poly(GMA-co-EDMA)**} & Immobilization of SNPs upon a polymer monolith. & RT & 60 min & 50 nm Ag & [127] \\ \hline \multirow{2}{*}{**Poly(HEMA-co-EDMA)**} & Generation of polymer monolith extraction device within a & & & & 20 nm iron & \multirow{2}{*}{[135]} \\  & pipette tip, immobilized with IONPs via surface grafted & RT & N/A & & \\  & functional groups (META). & & & & oxide \\ \hline \multirow{2}{*}{**Poly(NIPAAm-co-GMA-co-EDMA)**} & Generation of \(\gamma\)-alumina nano-particle monolith for PMME. & 60 & 14 h & 10–20 nm & \multirow{2}{*}{[136]} \\  & & & & Al\({}_{2}\)O\({}_{3}\) & \\ \hline \multirow{2}{*}{**Poly(GMA-co-EDMA)**} & Immobilization of Pd/Pt NFs via aminated surface groups. & RT & 72 h & Pd/Pt NFs & [137] \\  & **co-BuMA-co-EDMA)** & & & & \\ \hline \multirow{2}{*}{Poly(GMA-co-EDMA)} & Coating of monolith surface with graphene and graphene & RT & N/A & Graphene & \multirow{2}{*}{[138]} \\  & oxide nano-sheets for PMME. & & & & nano-sheets & \\ \hline \multirow{2}{*}{**Poly(GMA-co-EDMA)**} & Encapsulation of MWCNTs and surface attachment of & & & & \\  & MWCNTs via surface aminated groups. & RT & N/A & MWCNTs & [139] \\ \hline \hline \end{tabular}
\end{table} 
Table 4: _Cont._nano-particle diameter [142]. Generally, the AuNPs are formed _in vitro_ prior to addition to a preformed monolithic column [9,129,134]. Alternative methods can also be used, such as the mixing of the AuNP suspension with a reducing agent directly before entering the column, _i.e._, by use of a T-piece [131,133]. In numerous studies [9,129,134], the reactive monomers VAL or GMA were grafted to monoliths, in order to produce the typical surface for AuNP immobilization. Aminated and thiolated surfaces for AuNP immobilization were investigated; amination provided uniformly spaced nano-particles, whereas a thiolated surface produced sporadic aggregates of nano-particle clusters [134]. The aminated pathway generated a higher gold wt% content on the monolith surface relative to previously reported thiolated methods [131,133]. [PERSON] _et al_. produced a hypercross-linked column, which incorporated the use of both surface thiol groups and a secondary immobilization of amine groups (polyethyleneimine, PEI) [118].