Preparation of Cation Doping Precursor
A 0.12 M Mn(Ac)2 precursor was prepared by dissolving 1245.8 mg Mn(Ac)2 powder, into 50 mL ODE, and 10 mL OA. The metal cation dopant precursor was heated under N2 at 150 °C for 2 h. A mixture of OA–ODE (1:2) was used to further dilute the dopant precursor in flow.
Modular Fluidic micro-processor
The modular flow synthesis platform was constructed using three main modules: 1) precursor delivery, 2) reaction, and 3) spectral monitoring modules. The process flow diagram is shown in Figure S7, Supporting Information. The precursor delivery module included nine automated syringe pumps (seven Chemyx Fusion 6000 and two Chemyx Fusion 4000 syringe pump) loaded with gas-tight stainless steel syringes (nine 50 mL, Chemyx) and one automated mass flow controller (MFC, Bronkhorst, EL-Flow Select) for the controlled injection of liquid precursors and Ar into the fluidic micro-processor. All the syringes and MFC were connected to the fluidic junctions by fluorinated ethylene propylene (FEP) tubing (500 μm inner diameter, ID, 1.59 mm outer diameter, OD, 90 cm long). Both fluidic micro-processors were constructed using 750 μm ID FEP tubing. The CsPbBr3, SnCl4, PFO, and Ar streams were directed to a custom-designed five-port segmentation module to form a three-phase flow in the first fluidic micro-processor. The pristine NC stream was formed by mixing a concentrated CsPbBr3 NCs solution (4 mM) with pure toluene in a T-junction before entering the segmentation module. The SnCl4 stream was formed by in-flow mixing of the SnCl4 precursors in a four-way cross-junction (IDEX Health & Sciences) with OAm–TOL (1:2), OA–TOL (1:2), and pure TOL streams. Two in-line braided tubing were used to ensure uniform mixing of the CsPbBr3 and SnCl4 streams before entering the segmentation module. The Mn(Ac)2 stream was formed by in-flow mixing of the Mn(Ac)2 precursor with the OA–ODE (1:2) and pure ODE streams. The in-line injection of the metal cation doping precursor into the reactive phase droplet exiting micro-processor 1, before entering micro-processor 2, was accomplished through a T-junction. The total flow rates of the precursors in micro-processor 1, micro-processor 2, PFO, and Ar were set at 400, 250, 50, and 500 μL min−1, respectively. The spectral monitoring module consisted of two custom-machined flow cells, located at the end of each fluidic micro-processor for in situ PL spectroscopy of the in-flow doped LHP NCs. Each flow cell was connected to a fiber-coupled UV LED (365 nm, Thorlabs, M365LP1) as the only excitation light source, and a fiber-coupled spectrometer (Ocean Insight, Ocean HDX Miniature Spectrometer) in a 90° configuration. The in situ PL spectra were acquired using an integration time of 20 ms. To reduce the signal-to-noise ratio for the PL spectroscopy after cation doping reaction, the outlet of micro-processor 2 was connected to an adapter (IDEX union) to increase the FEP tubing ID to 1.59 mm (3.18 mm OD). The droplet formation stability and uniformity within the three-phase flow configuration in both microreactors were studied using the methodology reported in our previous work. The travel time of each phase passing through the flow cell was measured by monitoring the PL intensity at 400 nm in each flow cell.
Read Full Article Here: Autonomous Nanocrystal Doping by Self-Driving Fluidic Micro-Processors
Authors: Fazel Bateni,Robert W. Epps,Kameel Antami,Rokas Dargis,Jeffery A. Bennett,Kristofer G. Reyes,Milad Abolhasani.
Published Date: 13 March 2022