Given the environmental havoc wreaked by other seemingly beneficial substances, such as DDT, it is little wonder that we greet strange inventions like carbon nanotubes and quantum dots with skepticism, especially when we know so little about their long-term effects or toxicity [source: Goodman].
Further fueling these concerns are medical findings revealing the harmful effects of certain nanoparticles, such as carbon nanotubes, which cause lung granulomas (spheres of cells associated with disease) when inhaled by rats. The effects of other nanoparticles remain inconclusive -- particularly where humans are concerned -- but studies point to nanosized ingredients in some sunscreens as causing brain damage in mice and rainbow trout through oxidative stress [sources: Karn; Choi; Raloff].
Natural alternatives to nanoscale manufacturing may hold the key to mitigating such problems. In the case of sunscreen, for example, researchers have found a potentially safer nanoparticle in English ivy. The vine's notorious tenacity springs from a yellowish "super glue" exuded by its tendrils, which is composed of nanoparticles four times more effective as a sunblock than titanium dioxide or iron oxide. The particles are biodegradable, water-resistant and only block UV rays [source: Raloff].
Ideally, synthetic nanoscale construction would operate like a cell, using simple, nontoxic substances at room temperature to assemble a product from the ground up and then recycle or efficiently destroy the leftovers. Until such techniques are possible, green researchers are looking increasingly toward using natural processes for inspiration and for safe alternatives to solvents and other hazardous processes.
Researchers have already found ways to use certain bacteria to create nanospheres of selenium, tellurium, zinc selenide and cadmium selenide at room temperature, reducing reliance on high temperatures, pressures and dangerous chemicals [source: NNI, "U.S. Geological Survey (USGS)"].
Natural chemicals, such as the phytochemicals naturally occuring in plants, present another green alternative. Take nanoscale gold, a substance with applications in fuel cells, chemical sensors and biological tools [sources: Tufts; Greenberg]. What once required large amounts of flammable and explosive toxic solvents can now be made using only a gold salt (an electrically neutral compound of gold) and a solution of Darjeeling tea, cinnamon or cumin [sources: Schmidt, Nune et al.].
As exciting as the possibilities are, so far the most inspiring green nanotechnologies remain in the imaginations of researchers. If or when they are developed, they will need economic backing and market support to help them become affordable and achieve widespread use [source: Goodman].
Until then, we can all do our part to make the Earth a more sustainable place -- on every scale.