Graphene Quantum Dots: Introduction and Market News - Page 7

Researchers from the Chinese Jilin University, along with Louisiana State University, succeeded in making graphene-enhanced quantum dot-light emitting diodes (QD-LEDs). They fabricated QD-LEDs which show better current efficiency and power efficiency than similar ITO-based devices working at a low current density. The result indicates that graphene can be used as anodes to replace indium tin oxide (ITO) in QD-LEDs.

Single layer graphene was introduced as an electrode into the QD-LED. Graphene-based QD-LEDs performed as well as ones based on ITO anodes and the maximum brightness could meet the minimum brightness requirement of display applications. It demonstrates that single-layer graphene film has great potential to be used in QD-LEDs as an anode. The researchers are now focusing on searching for higher efficiency QDs and optimizing device structures to further improve the efficiency.

Reseachers from the University of Sydney managed to create graphene quatum dots that shine nearly five times brighter than regular dots. These powerful dots can be used for bio-imaging, like capturing images of internal organs or be injected into the body to detect cancer cells. They are even much less toxic compared to current dots for internal use. Other possible uses include ultra-bright LEDs, like the ones in screens or signs, or even batteries with long-life and faster charging times.

The researchers used ultrasound to break graphene sheets into atom-scale dots, then used potassium hydroxide to enhance the surface area of these dots. They increased the surface area by six times to get the dots to fluoresce almost five timer brighter than conventional dots. 

In 2013, Rice University researchers developed a simple method to reduce coal into graphene quantum dots (GQDs). Now the researchers combined these GQDs with small graphene oxide (GO) sheets to create an excellent catalyst for fuel-cells.

To create the new materials, the researchers boiled a solution of GQDs and GO sheets - which combined them into self-assembling platelets. Treating those platelets with nitrogen and boron created a material with an abundance of edges for chemical reactions (for oxygen reduction), and excellent conductivity.

Researchers from from Zhejiang Normal University in China developed a biocompatible bio-sensor that can simultaneous detection multiple biomarkers, such as DNA and proteins. Those sensors are made from carbon materials - mainly graphene-oxide (GO) and graphene quantum dots (GQDs).

The researchers explain hat GQDs rae promising environmentally friendly and biocompatible nanomaterials that can be used to design new fluorescence detection platforms in vitro and in vivo. The researchers use the specifically designed fluorescence on-off-on process that takes advantage of the intense and dual-color fluorescence of the GQDs, in addition to the efficient quenching effect of GO. The high emission efficiency of GQDs guarantees the high sensitivity of the constructed biosensors, while the good biocompatibility is promising for use of biosensors in vivo.

Researchers from the Korean's KAIST institute developed a new process to produce graphene quantum dots that are equal in size and highly efficient in emitting light. Quantum Dots potentially can be used to develop emissive flexible displays (similar to OLED displays), and this development may enable those displays to be graphene-based.

The process involves mixing salt, water and graphite and then synthesizing a chemical compound between layers of graphite. All the resulting quantum dots were 5 nanometer in diameter, and these QDs do not contain and heavy metals (like current commercial quantum dots). The process is reportedly easy to scale and should not be expensive.

Researchers are developing flash memory devices that store the charge in nanocrystals instead of the usually used polysilicon layers. These kinds of devices are less sensitive to local defects and offer high-density memory potential.

Researchers from Samsung Electronics (and Korea's Kyung Hee University) are now developing similar flash devices based on graphene quantum dots (GQDs). The performance of such a device is promising, with an electron density that is comparable to semiconductor and metal nanocrystal based memories. Those flash memory can also be made flexible and transparent.

Researchers from MIT and the University of California at Berkeley developed a new way to evenly functionalize graphene with oxygen at low (50-80 C) temperatures. The method is environmentally friendly (no harsh chemical treatment) and can be applied on a large scale.

The researchers use low-temperature annealing and this cause the oxygen atoms to form clusters. This leaves areas of pure-graphene between the oxygen clusters. This decreases the graphene's electrical resistance by four to five orders of magnitude (the oxygen clusters are insulating) which is good for applications such as sensing, electronics and catalysis.

Researchers from Rice University developed a simple method to reduce coal into graphene quantum dots (GQDs). Different types of coal produce differently-sized quantum dots (ranging from 2 to 20 nanometers). The yield is also very good - about 20% of the coal can be turned into GQDs. Those GQDs are water-soluble and non toxic (according to early tests).

This is a chemical method - the coal is crushed and than soaked in acid solutions (nitric and sulfuric acids) for 24 hours. This breaks the bonds that hold the tiny GQDs together.

Researchers from the Universities of Bielefeld and Ulm (both in Germany) developed a new way to produce graphene using aromatic molecules. This new process enables the production of large sheets and also small flakes, quantum dots and nanoribbons (GNRs). It could also be used to create multi-layered graphene.

The researchers start with copper single-crystals or low-cost polycrystalline copper foils as substrates. They then deposit aromatic biphenyl thiol molecules in a self-organised single layer. Finally, the irradiate the deposited materials using low-energy electrons and then thermal process it. This turns the bipheyl thiol into graphene.

Researchers from China's Beijing Institute of Technology developed new supercapacitors based on electrodes made from graphene quantum dot (GQD) assemblies on horizontally aligned carbon nanotubes (HACNTs). They say that adding the GQD results in more than 200% capacitance improvement compared to bare HACNT electrodes.

To fabricate these devices, the researcher synthesized super-long vertically aligned CNTs (VACNT) (using water-assisted CVD) and then transformed hem into HACNTs using a roller. The GQD were uniformly anchored on the HACNTs using an electrochemical deposition process. The composite film that was producing in this method was assembled in a symmetrical two-electrode configuration.