Using Size-Exclusion Chromatography to Evaluate Changes in the Sizes of Au and Au/Pd Core/Shell Nanoparticles Under Thermal Treatment

Abstract

In this study, we used size-exclusion chromatography (SEC) to evaluate the sizes of Au and Au/Pd core/shell nanoparticles (NPs) that had been subjected to thermal treatment, with the eluted NPs monitored through diode array detection (DAD) of the surface plasmon (SP) absorption of the NPs. In the absence of an adequate stabilizer, thermal treatment resulted in longer retention times for the Au NPs and shorter retention times for the Au/Pd core/shell NPs in the SEC chromatograms. Thus, thermal treatment influenced the sizes of these Au and Au/Pd core/shell NPs, through digestive ripening and Ostwald-type growth, respectively. In addition, the trends in the SP absorption phenomena of the NPs in the eluted samples, as measured using DAD, were consistent with the trends of their size variations, as measured from their elution profiles. In the presence of 3A-amino-3A-deoxy-(2AS,3AS)-b-cyclodextrin (H 2 N-b-CD) as a stabilizer, the retention times and SP absorptions of the eluted Au and Au/Pd NP samples remained constant. Thus, H 2 N-b-CD is a good stabilizer against size variation duration the thermal treatment of Au and Au/Pd core/shell NPs. A good correlation existed between the sizes obtained using SEC and those provided by transmission electron microscopy. Therefore, this SEC strategy is an effective means of further searching for suitable stabilizers for NPs, especially those exposed to harsh reaction conditions (e.g., in catalytic reactions).

Using Size-Exclusion Chromatography to Monitor Variations in the Sizes of Microwave-Irradiated Gold Nanoparticles

“…were separated in the presence of a mobile phase additive (10 mM SDS) at a flow rate of 1.0 mL min −1 . Accordingly, we found that the four differently sized Au NPs had different elution times; the sequence of elution times (increasing with decreasing Au NP size) paralleled the elution behavior described previously [37]. For SEC to be used practically for the routine analysis of NP sizes, it was necessary for us to validate the reproducibility of the elution times because it influences the precision of the size-characterization process.…”

“…In addition, we have recently employed SEC approaches to determine a suitable stabilizer for NPs under conditions mimicking the temperatures found in catalysis environments (ca. 100 • C) [37] and to rapidly monitor the sizes of Au NPs in the presence of salt or organic environments to determine the effects of the stabilizers of Au NPs in these media [40]. Our results, combined with the prevalence of automated SEC systems, suggest that this approach is superior to other techniques (e.g., DLS and TEM) typically employed for the characterization of NPs [33].…”

“…In each chromatogram, the intensity of the signal for the Au NPs decreased. In addition, the retention time lengthened slightly upon increasing the heating temperaturepresumably a result of digestive ripening, which decreases the sizes of citrate-capped Au NPs [25,37]. We used the calibration curve in Figure 1 to obtain the sizes of the fabricated NPs from the elution times in the SEC chromatograms of the NPs.…”

“…In addition, techniques that can be performed using a small volume of a single sample within a short analysis times and at a low operating cost are of interest for the separation NPs into their constituent sizes [33]. Relative to other separation techniques (e.g., centrifugation, high-performance liquid chromatography (HPLC) [9], capillary electrophoresis [34], diafiltration [35], and gel electrophoresis [36]), size-exclusion chromatography (SEC) has the advantageous features of short analysis times, low operating costs, and high reliability, with the potential for in situ analysis and in situ gathering of spectroscopic data of the individual separated NPs [37].…”

Size-exclusion chromatography of metal nanoparticles and quantum dots

“…SEC was also employed for stability studies of Au NP solutions [19–21]. A polymer-based (styrene/divinylbenzene) column and 10 mmol L −1 SDS mobile phase were used in all of these studies.…”