Environmental Science: Nano Blog

Scientists have developed a method to remove a common persistent pollutant in under 10 minutes using metal nanoparticles supported on genetically modified viruses. Each metal-studded virus acts as a tiny battery, electrochemically reducing the pollutant to a less toxic compound.

Para-chloronitrobenzene is a carcinogen and toxic when inhaled, consumed or absorbed through the skin. It is widely used in dyes, synthetic materials and pesticides. As a persistent organic pollutant, it accumulates in lakes and rivers, where it sticks around for decades. A common method of reducing the compound to the safer para-chloroaniline uses metal nanoparticles, often iron. However, this method is slow and requires like high temperature or high acidity. Moreover, with continued use, nanoparticles tend to clump together, which makes them much less effective.

Now, Huimin Yu and colleagues from Tsinghua University in China can reduce chloronitrobenzene in less than 10 minutes using genetically modified viruses. They decorated the outside of the viruses with iron and nickel nanoparticles; the difference in electric potential between the metals converts the viruses into micro-batteries, which can reduce more chloronitrobenzene in the same time than simple iron nanoparticles.

Source: © Shutterstock

Scientists from Austria and Switzerland have developed a new way to distinguish engineered nanoparticles from naturally occurring nanoscale particles in soil samples. The method works even at concentrations orders of magnitude below natural background levels.

Everyday items, such as cosmetics and textiles, increasingly contain nanoparticles. Concerns regarding nanoparticles’ potential impact on health and the environment mean regulators want to monitor synthetic nanoparticle (for example TiO₂, SiO₂ and CeO₂) levels in the environment. However, samples often contain natural nanoparticles of similar size and composition, often at much higher concentrations. Conventional single-particle inductively coupled plasma mass spectrometry (spICP-MS), where the instrument locks onto one isotope, is unable to tell them apart.

After working in the area for several years, Frank von der Kammer and Thilo Hofmannfrom the University of Vienna and co-workers have now made a breakthrough based on multi-elemental fingerprinting to explore differences, such as elemental ratio, between engineered and natural nanoparticles. The team tested the concept using an instrument, developed by colleagues at the Swiss Federal Institute of Technology (ETH) in Zurich, that enables single particle analysis on a time-of-flight mass spectrometer (TOFMS). The prototype spICP-TOFMS instrument is so fast, it not only measures all of the different elements simultaneously, it does so for every particle. They then developed a machine-learning algorithm to train the analytical system, using well-defined standards of both types of nanoparticles, to increase the speed and precision of the analysis.

Read the full article in Chemistry World.

Brassica juncea, a type of mustard plant, absorbs heavy metals through its roots. Source: © iStock

Plants partial to a diet of heavy metals are an ideal raw material for nanomaterials once they have cleaned up contaminated soil. So says a team of Chinese scientists behind a method that turns this vegetation into nanoparticles and nanotubes.

Heavy metals are naturally occurring elements with important industrial, agricultural and technological uses. Many human activities such as mining and industry lead to the local build-up of toxic heavy metals in soil and groundwater. Typically toxic and carcinogenic, their release into the environment is a major concern as they can accumulate in the food chain, damaging the health of wildlife and humans alike.

Certain plant species known as hyperaccumulators can grow in soil contaminated with heavy metals. They absorb the metals through their roots and concentrate them in their own tissues – a genetic trait designed to make themselves toxic to hungry herbivores. These plants have been used in the past to clean up contaminated areas; a technique called phytoremediation. Once the plants have extracted the metals, they themselves need to be removed, as if left to complete their natural lifecycle they would simply return the metals to the soil. The metal-containing plant waste is often incinerated.

Now, Jiao Qu and his team at Northeast Normal University in China have used this biomass as a raw material to make useful nanomaterials.