GO/AIE probes with high FL properties using a VFD platform

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Graphene oxide (GO) has been well recognized as an effective fluorescence (FL) quenching material that reduces the brightness of fluorophores, even for aggregation-induced emission luminogens (AIEgens). A limited number of studies have demonstrated that GO enhanced the FL property of AIEgens, with slight increasing in relative FL intensity occurring at a specific GO concentration. Our recently published research detailed here introduced a dynamic thin-film microfluidic platform, known as vortex fluidic device (VFD), to produce GO/AIE probes with the property of high FL, which is without precedent. The employment of VFD delivers mechanical energy for controlling chemical transformations and tuning the properties of GO/AIE probe under various rotation speeds and water fractions, allowing processing beyond batch production and with cost-effective commercialization potentials.

Incorporating TPE-2BA, a derivative of tetraphenylethylene with 2 boronic acid groups, we prepared highly fluorescent GO/AIE probes exhibiting ~4- or ~14-fold increase in relative FL intensity compared to that of GO/AIE materials prepared by batch processing or AIE alone, respectively (Figure 1a). The brightness of the TPE-2BA particles depended on the final water fraction (WF), with FL intensity negligible for WF < 70%, then increasing in tracking towards WF = 80%. We observed that the addition of GO at the concentration of 0.0025 mg/mL to the TPE-2BA solution resulted in brighter particles at WF = 80% compared to the TPE-2BA alone with 110% enhancement in the FL relative intensity (Figure 1b).

Figure 1. FL relative intensities for AIE and GO/AIE probes, prepared under different condition with effects of (a) GO and VFD at WF =80% and (b) different WFs.

Interestingly, the preparation of GO/TPE-2BA under the shear stress induced by the VFD rotating tube resulted in much brighter probes with significantly enhanced (62-fold) relative FL intensities compared to the quenching state at 5000 RPM, occurring at the rotation speed of 1500 RPM (Figure 2a). In general, we observed that for a specific WF and GO concentration (80% and 0.0025 mg/mL, respectively), the addition of GO enhanced the FL property of TPE-2BA particles with a ~1-fold increase in the relative FL intensity (Figure 2b). When a VFD was recruited, much brighter GO/TPE-2BA probes were prepared at rotation speeds up to 2000 RPM. At 1500 RPM the GO/TPE-2BA was significantly brighter, compared to the batch production, with a ~4-fold increase. At rotation speeds > 2000 RPM, GO quenched the FL property of TPE-2BA particles with an 80% reduction in the relative FL intensity, compared to that from batch production, occurring at 5000 RPM (Figure 2b). High stability of the GO/TPE-2BA probes that were produced at 1500 RPM and WF = 80% was observed with less than 6% and 10% reduction in the FL maxima at 15 and 28 days, respectively (Figure 2b; inset).

Figure 2. (a) Change in relative FL intensity of GO/TPE-2BA probe as a function of VFD tube rotational speed at wf =80%. (b) A general overview indicating the effect of GO and VFD on the relative FL intensities of TPE-2BA and GO/TPE-2BA prepared in batch (GO/TPE-2BA) and using a VFD (GO/TPE-2BA+VFD), and the stability of GO/TPE-2BA+VFD at 15 and 28 days (inset).

Overall, a simple, novel and cost-effective method for the preparation of GO/AIE probes with high FL properties involving the use of a VFD platform has been established. The method affords highly bright GO/AIE probes with >14-fold increase in the relative FL intensity compared to that of AIE fluorogen alone.

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Vortex fluidic enabling and significantly boosting light intensity of graphene oxide with aggregation induced emission luminogen

Javad Tavakoli, Nikita Joseph, Clarence Chuah, Colin L. Raston and Youhong Tang

Mater. Chem. Front., 2020, Advance Article

http://dx.doi.org/10.1039/D0QM00270D

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通讯作者简介

Youhong Tang 教授

Flinders University, Australia

MCF Community Board member

Professor Youhong Tang obtained his PhD degree from the Hong Kong University of Science and Technology in 2007. He moved to Flinders University with an ARC-DECRA in 2012 from the University of Sydney. As a material science and engineering researcher, his research interests mainly focus on the structure-process-property relations of multifunctional and value-added materials and composites, especially incorporating novel aggregation-induced emission luminogens.