Dots, rods and tetrapods: CdSe gets in shape


Jan 31, 2011

QDOTS imagesCAKXSY1K 8Researchers from the South China University of Technology have presented a surfactant-free recipe for fabricating high-quality CdSe nanocrystals (NCs). The morphology, which includes irregular dots, rods, tetrapods and sphere-shapes, can be controlled easily by varying the experimental conditions. More importantly, the preparation techniques involved are simple, low-cost and can be used to fabricate other II-VI group semiconductor NCs.

CdSe Nanocrystals

CdSe nanocrystals: dots, nanorods and tetrapods

The CdSe NCs were produced with a fixed Cd/Se molar ratio of 2:1 and using 2.32 g of trioctylphosphine oxide (TOPO); at the same time, all the trioctylphosphine selenide (TOPSe) injections were kept at 1 ml, but with different concentrations. No other ligands were used in the case study.

Homogeneous CdSe NCs with different morphology were obtained under such experimental conditions. The sample quality (size distribution, optical properties, tetrapod selectivity) is as good as that of the best CdSe NCs synthesized by using extra ligands. As for the growth mechanism, we believed that the decomposition of TOPSe and cadmium myristate at a temperature of 240 or 300 °C would also supply in situ-generated TOP and myristic acid in the reaction mixture, which affected the anisotropic growth of CdSe NCs.

To further investigate the application of this surfactant-free recipe, the group is now optimizing the experimental conditions and has found that well controlled morphology of CdTe and/or CdSexTe1–x NCs can also be successfully fabricated.

Thanks to the easily controllable NC-growth kinetics, such a synthesis route is very promising for low cost, large-scale preparation of CdSe and CdTe NCs for application in solution-processed thin-film solar cells.

More information can be found in the journal Nanotechnology.

About the author

The study was funded by the National Natural Science Foundation of China (nos. 50703012, 50773023 and 50990065), the National Basic Research Program of China (973 program no. 2009CB623600) and SCUT grant (no. 2009ZZ0003). The experiments were performed at the Institute of Polymer Optoelectronic Materials and Devices, Key Laboratory of Special Functional Materials group. Hongmei Liu is a PhD student in materials science and holds a bachelors degree in chemistry. Currently she is exploring the fabrication of high-quality semiconductor nanostructures, together with the measurement and application of the resulting nanostructures in the field of solution processed thin-film solar cell systems and other nano-electronic devices.

QMC receives U.S. patent for synthesis of Group II-VI inorganic tetrapod quantum dots


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*** Note to Readers: In our efforts to provide timely updates in the world of “Nano”, we post the following announcement. We have previously posted about this company and find the premise of the technology to be very promising IOHO. We appreciate your thoughts, comments and responses as to how you think this technology will impact the industry, specifically in Nano-Bio, Nano-Pharma and Nano-Medicine.  Cheers!  BWH

Published on November 21, 2012 at 12:11 AM

quantum material corp logoQuantum Materials Corporation, Inc. (OTCQB: QTMM) proudly announces the USPTO patent grant of a fundamental disruptive technology for synthesis of Group II-VI inorganic tetrapod quantum dots. The patent, “Synthesis of Uniform Nanoparticle Shapes with High Selectivity” and invented by Professor Michael S. Wong’s group at William Marsh Rice University, Houston, TX, for the first time gives precise control of both QD shape and dimension during synthesis and is adaptable to quantum dots production of industrial scale quantities. The new synthesis is a greener method using surfactants as would be found in laundry detergent instead of highly toxic chemicals used during industry standard small batch synthesis.

Quantum Materials Corporation, Inc.(QMC) has acquired the exclusive worldwide license for this patent and its wholly owned renewable energy subsidiary, Solterra Renewable Technologies, has the same rights specific to Quantum Dot Solar Applications.  QMC last week announced a high quantum yield of 80% for a new class of tetrapod QD synthesized with this patented process.

According to a new market research report, “Quantum Dots (QD) Market – Global Forecast & Analysis (2012 – 2022)” published by MarketsandMarkets (http://www.marketsandmarkets.com), the total market for Quantum dots is expected to reach $7.48 Billion by 2022, at a CAGR of 55.2% from 2012 to 2022.

The Rice University QD synthesis remarkably produces same-sized tetrapods, in which more than 92+ percent are full tetrapods, with a similar high degree of process control over QD shape, size, uniformity, and selectivity. The synthesis is applicable to a wide range of mono and hybrid Group II-VI tetrapod QD with/without shell and can optimize specific characteristics by modifying process parameters.

Across the broader QD industry however, other companies have been striving to increase production, but none have predicted scaling quantum dot production remotely close to multiple kilograms per day.

Quantum Materials Corporation’s development of breakthrough software-controlled continuous flow chemistry process allows scaling of tetrapod quantum dot production to 100Kg/Day. Increasing production will transform tetrapod quantum dots from a novelty to a commodity, available across industries and applications where prior limited availability and high prices restricted product development. For example, 100Kg daily QD production can support a QD Solar Cell Plant producing one Gigawatt/year of R2R flexible QD solar cells at an industry competitive .75 cents/Watt at the start.

Tetrapod QD offer inherent advantages over spherical QD including higher brightness, truer and more colors, the use of less active material (QDs) for any application, higher photostability and therefore longer lifetime; which together more than justify their product development. OLEDs, for example, share design architecture similarities and would not require entirely new research to adapt to TQD-LEDs.  Spherical Quantum dots, at the low price of $2000/gm. are 30 times more expensive than gold today.

It simply has not been economically feasible to commercialize QD applications due to their high cost, which stems from the difficulty of small batch manufacture, the inability to produce uniform, same size QD from batch to batch, and to promise a reliable, timely supply. Over the last half dozen years university and corporate quantum dot research has increased dramatically and there are ready QD applications that may now be “business planned” for joint ventures or possible licensing with Quantum Materials Corporation and Solterra Renewable Technologies.

Stephen B. Squires, CEO and President of Quantum Materials Corporation, Inc. and Solterra Renewable Technologies, Inc., said, “With the granting of the US Patent, tetrapod quantum dots are well positioned to revolutionize several industries in offering dramatic performance at cost effective levels. While the technology has been under review, we have continued to execute our vision to establish global manufacturing centers and strategic partnerships for creating dramatic value in our companies.”  Squires continued, “We are excited to continue our business plan with the IP protection offered by the granted allowances. Adoption of quantum dots will result in new classes of products with advanced features, improved performance, energy efficiency, and lower cost.”

Art Lamstein, Director of Marketing for QMC and SRT added, “The timeline is moved forward to present day and market forecasts will need be rewritten for quantum dot based renewable energy, photovoltaics, biotech diagnostic assays, drug delivery platforms, theranostic cancer and other biomedicine treatments, QD-LED and opto-electronic devices, photonics, low power SSL lighting, batteries, fuel cells, thermo-QD  applications, quantum computing, memory, and conductive inks (to name a few).”QDOTS imagesCAKXSY1K 8