Quantum dot technology helps decontaminate water supplies

Quantum dots are being explored for various applications, especially in medicine and the environment. Many quantum dots used in electronics are made from toxic substances. Researchers are now able to develop non-toxic quantum dots, which is a huge step forward in making them more widely applicable. They are focusing on carbon—and sulfur-based quantum dots, using them to create safer invisible inks and to help decontaminate water supplies.

Quantum dots are synthetic nanometer-scale semiconductor crystals that emit light. They have a wide range of applications, including electronic displays and solar cells.

“Many conventional quantum dots are toxic because they’re derived from heavy metals,”  explains Md Palashuddin Sk, an assistant professor of chemistry at Aligarh Muslim University in India.  “So, we’re working on nonmetallic quantum dots because they’re environmentally friendly and can be used in biological applications.”

Quantum dots are incredibly small, often only consisting of tens of atoms in diameter. Their behavior is influenced by quantum effects, which makes them behave differently than larger objects. One of the surprising properties of quantum dots is that they emit light differently; for instance, gold material appears blue at this scale.

Researchers have explored nonmetallic quantum dots as a bioimaging tool. Meanwhile, Palashuddin is focused on developing carbon- and sulfur-based quantum dots (Cdots and Sdots, respectively) for various other applications.

“Carbon and sulfur are very abundant, cost-effective materials, and they can easily be synthesized into quantum dots,”  he says.  “You can make carbon dots from waste materials, then use them for removing pollutants — they’re a way to make the process come full circle.”

Despite relatively new discoveries, Palashuddin has been able to utilize Cdots and Sdots in various ways. The dots’ large surface area makes modifying them for different applications easy.

Previously, the team had created dots that emit different colors based on the contaminants they come into contact with. This feature allows for the identification of contaminants in water samples, such as lead, cobalt, and chromium, without leaching any new metals from the dots themselves.

In addition to identifying contaminants, Cdots can help break down pollutants like pesticides and dyes in water. In a project, Palashuddin and Amaresh Kumar Sahoo collaborated to form Cdots from potato peels and mount them on microscopic robots. These robots were designed to target and degrade toxic dyes in samples that simulate polluted water.

The team has developed methods to remove contaminants from water entirely rather than just identifying or degrading them. They’ve designed Cdots to sop up automotive oil and are currently exploring a Cdot-based filter system to help treat oil spills.

Next, the researchers plan to apply their laboratory findings in the field, perhaps in a project focused on the Yamuna River. This river is notorious for being heavily contaminated, especially in more populated areas. Palashuddin and his team aim to leverage their nonmetallic dots to detect and separate the various pollutants present in the river, such as pesticides, surfactants, metal ions, antibiotics, and dyes. They hope to functionalize the dots to capture as many different contaminants as possible, making it easier to remove them.

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Taxonomy

• Contaminant Removal
• Contaminant Movement Mapping