Name: a modular microfluidic technology for systematic studies of colloidal semiconductor nanocrystals
Uploaded: 2018-05-10T15:00:00
Description: Watch this Scientific Journal Video about A Modular Microfluidic Technology for Systematic Studies of Colloidal Semiconductor Nanocrystals at JoVE.com

The authors gratefully acknowledge the financial support provided by North Carolina State University. Milad Abolhasani and Robert W. Epps gratefully acknowledge financial support from the UNC Research Opportunities Initiative (UNC-ROI) grant.

1. Reactor Assembly
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57666/57666fig1.jpg" /> 
Figure 1. Step-by-step illustration of a sample platform assembly process. The panels shows a step-by-step illustration of a sample platform assembly process detailing (i) the initial arrangement of the translation stage and optical post holders on the mounting bread broad, (ii) the mounting of the precursor t...

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W., Yu, Y., Dou, L., Yang, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solution-phase+synthesis+of+cesium+lead+halide+perovskite+nanowires.">Solution-phase synthesis of cesium lead halide perovskite nanowires.</a> Journal of the American Chemical Society. 137 (29), 9230-9233 (2015).</li><li>Lignos, I., Stavrakis, S., Nedelcu, G., Protesescu, L., deMello, A. J., Kovalenko, M. 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W., Felton, K. C., Coley, C. W., Abolhasani, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Automated+microfluidic+platform+for+systematic+studies+of+colloidal+perovskite+nanocrystals:+towards+continuous+nano-manufacturing.">Automated microfluidic platform for systematic studies of colloidal perovskite nanocrystals: towards continuous nano-manufacturing.</a> Lab Chip. 23 (17), 4040-4047 (2017).</li><li>Lignos, I., Protesescu, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Facile+droplet-based+microfluidic+synthesis+of+monodisperse+IV-VI+semiconductor+nanocrystals+with+coupled+in-line+NIR+fluorescence+detection.">Facile droplet-based microfluidic synthesis of monodisperse IV-VI semiconductor nanocrystals with coupled in-line NIR fluorescence detection.</a> Chemistry of Materials. 26 (9), 2975-2982 (2014).</li><li>Park, J., Saffari, A., Kumar, S., G&#252;nther, A., Kumacheva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+synthesis+of+polymer+and+inorganic+particulate+materials.">Microfluidic synthesis of polymer and inorganic particulate materials.</a> Annual Review of Materials Research. 40 (1), 415-443 (2010).</li><li>Phillips, T. 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Automated sampling system: The autonomous operation of the screening platform is carried out with a central control finite state machine. Movement between these states occurs sequentially with multiple recursive segments to allow for operation across a varying number of sampling conditions. The general system controls can be divided into 3 core stages. First, the system begins with an initialization step, which establishes communications through each USB-controlled component, automatically defines file s...

The advent of semiconductor nanocrystals, particularly quantum dots, has driven significant advancements in electronic materials research and manufacturing. For example, quantum dot LEDs1 have already been implemented in commercially available &#34;QLED&#34; displays. More recently among this class of semiconductors, perovskites have sparked substantial interest and research towards high-efficiency and low-cost PV technologies. Since the first demonstration of a perovskite-based PV in 2009,2 the lab-scale power conversion efficiency of perovskite-based solar cells has increased at a rate unparalleled by any PV technology in history.3,4 In addition to the driving interest in perovskite-based PVs, a variety of recent methods describing the facile colloidal synthesis of perovskite nanocrystals have created the opportunity for low-cost, solution-phase processing of perovskite QDs in commercial electronics.5,6,7,8,9,10,11,12,13,14
In the effort towards large-scale nanomanufacturing of colloidal perovskite QDs, a better fundamental understanding of the nanocrystal growth pathways and an effective control of the reaction conditions must first be developed. However, existing studies of these processes have traditionally relied on flask-based approaches. Batch synthesis strategies present a variety of inherent limitations in terms of material characterization and production, but most significantly, flask-based techniques are highly inefficient in screening time and precursor consumption, and demonstrate flask size-dependent mass transfer properties, which inhibit the synthesis consistency.15 To effectively study the growth pathways of colloidal semiconductor nanocrystals across the large variety of reported syntheses procedures and within the broad relevant sample space, a more efficient screening technique is required. Over the past two decades, a range of microfluidic strategies have been developed for studies of colloidal nanocrystals leveraging the substantially lower chemical consumption, the accessibility of high-throughput screening methods, and the potential for a process control implementation in continuous synthesis systems.12,16,17,18,19,20
In this work, we report the design and development of an automated microfluidic platform for the high-throughput in situ studies of colloidal semiconductor nanocrystals. A novel translating flow cell, a highly modular design, and the integration of off-the-shelf tubular reactors and fluidic connections form a unique and adaptable reconfigurable platform with direct applications in the discovery, screening, and optimization of colloidal nanocrystals. Capitalizing on the translational capability of our detection technique (i.e., a three-port flow cell), for the first time, we demonstrate the systematic decoupling of mixing and reaction timescales, while simultaneously improving the sampling efficiency and collection rates over traditional stationary flow cell approaches. The utilization of this platform enables the high-throughput and precise band-gap engineering of colloidal nanocrystal syntheses towards continuous nanomanufacturing strategies.

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			<td height="21" style="height:21px;width:272px;">Toluene</td>
			<td style="width:191px;">Fisher Scientific</td>
			<td style="width:168px;">AC364410010</td>
			<td style="width:257px;">99.85% extra over molecular sieves</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Oleic acid</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td style="width:168px;">364525&#160;ALDRICH</td>
			<td>technical grade 90%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Cesium hydroxide (50 wt% in water)</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td style="width:168px;">232041 ALDRICH</td>
			<td>50 wt% in water &#62; 99.9% trace metals</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Lead(II) oxide</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td style="width:168px;">211907 SIGMA-ALDRICH</td>
			<td>&#62; 99.9% trace metals basis</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Tetraoctylammonium bromide</td>
			<td style="width:191px;">Sigma Aldrich</td>
			<td style="width:168px;">294136 ALDRICH</td>
			<td>98%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1/16&#34; OD, 0.04&#34; ID FEP tubing</td>
			<td style="width:191px;">MicroSolv</td>
			<td style="width:168px;">48410-40</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1/16&#34; OD, 0.02&#34; ID ETFE tubing</td>
			<td style="width:191px;">MicroSolv</td>
			<td style="width:168px;">48510-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">0.02&#34; thru hole PEEK Tee</td>
			<td style="width:191px;">IDEX Health &#38; Science</td>
			<td style="width:168px;">P-712</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1/4-28 ETFE flangeless ferrule for 1/16&#34;</td>
			<td style="width:191px;">IDEX Health &#38; Science</td>
			<td style="width:168px;">P-200N</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">1/4-28 PEEK flangeless nut for 1/16&#34;</td>
			<td style="width:191px;">IDEX Health &#38; Science</td>
			<td style="width:168px;">P-230</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">4-way PEEK L-valve</td>
			<td style="width:191px;">IDEX Health &#38; Science</td>
			<td style="width:168px;">V-100L</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Syringe pump</td>
			<td style="width:191px;">Harvard Apparatus</td>
			<td style="width:168px;">70-3007</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">8 mL stainless steel syringe</td>
			<td style="width:191px;">Harvard Apparatus</td>
			<td style="width:168px;">70-2267</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">25 mL glass syringe</td>
			<td style="width:191px;">Scientific Glass Engineering</td>
			<td style="width:168px;">25MDF-LL-GT</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Optical breadboard</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">MB1224</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">300 mm translation stage</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">LTS300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Optical post</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">TR2-4</td>
			<td>TR2, TR3, or TR4</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Optical post holder</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">PH4-6</td>
			<td>PH4 or PH6</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">365 nm LED</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">M365LP1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">LED driver</td>
			<td style="width:191px;">ThorLabs</td>
			<td style="width:168px;">LEDD1B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">600 micron patch cord</td>
			<td style="width:191px;">Ocean Optics</td>
			<td style="width:168px;">QP600-1-SR</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Deuterium-halogen light source</td>
			<td style="width:191px;">Ocean Optics</td>
			<td style="width:168px;">DH-2000-BAL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Miniature spectrometer</td>
			<td style="width:191px;">Ocean Optics</td>
			<td style="width:168px;">FLAME-S-XR1-ES</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Multifuction I/O device (DAQ)</td>
			<td style="width:191px;">National Instruments</td>
			<td style="width:168px;">USB-6001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:272px;">Virtual Instrument Software</td>
			<td style="width:191px;">National Instruments</td>
			<td style="width:168px;">LabVIEW 2015 SP1</td>
			<td></td>
		</tr>
	</tbody>
</table>

a modular microfluidic technology for systematic studies of colloidal semiconductor nanocrystals

Colloidal semiconductor nanocrystals, known as quantum dots (QDs), are a rapidly growing class of materials in commercial electronics, such as light emitting diodes (LEDs) and photovoltaics (PVs). Among this material group, inorganic/organic perovskites have demonstrated significant improvement and potential towards high-efficiency, low-cost PV fabrication due to their high charge carrier mobilities and lifetimes. Despite the opportunities for perovskite QDs in large-scale PV and LED applications, the lack of fundamental and comprehensive understanding of their growth pathways has inhibited their adaptation within continuous nanomanufacturing strategies. Traditional flask-based screening approaches are generally expensive, labor-intensive, and imprecise for effectively characterizing the broad parameter space and synthesis variety relevant to colloidal QD reactions. In this work, a fully autonomous microfluidic platform is developed to systematically study the large parameter space associated with the colloidal synthesis of nanocrystals in a continuous flow format. Through the application of a novel translating three-port flow cell and modular reactor extension units, the system may rapidly collect fluorescence and absorption spectra across reactor lengths ranging 3 - 196 cm. The adjustable reactor length not only decouples the residence time from the velocity-dependent mass transfer, it also substantially improves the sampling rates and chemical consumption due to the characterization of 40 unique spectra within a single equilibrated system. Sample rates may reach up to 30,000 unique spectra per day, and the conditions cover 4 orders of magnitude in residence times ranging 100 ms - 17 min. Further applications of this system would substantially improve the rate and precision of the material discovery and screening in future studies. Detailed within this report are the system materials and assembly protocols with a general description of the automated sampling software and offline data processing.

Sample spectra:&#160;Utilizing the discussed microfluidic platform, the nucleation and growth stages of colloidal semiconductor nanocrystals at the synthesis temperature can be directly studied by monitoring the time-evolution of the absorption and fluorescence spectra of the formed nanocrystals under uniform mixing conditions. Figure 5A shows an example set of spectra obtained within a single pass of the three-port flow cell...

Watch this Scientific Journal Video about A Modular Microfluidic Technology for Systematic Studies of Colloidal Semiconductor Nanocrystals at JoVE.com

A Modular Microfluidic Technology for Systematic Studies of Colloidal Semiconductor Nanocrystals

Detailed herein are the operation and assembly protocols of a modular microfluidic screening platform for the systematic characterization of colloidal semiconductor nanocrystal syntheses. Through fully adjustable system arrangements, highly efficient spectra collection may be carried out across 4 orders of magnitude reaction time scales within a mass transfer-controlled sampling space.

Colloidal semiconductor nanocrystals, known as quantum dots (QDs), are a rapidly growing class of materials in commercial electronics, such as light ...

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