Seven years ago, Northeastern University physics pro­fessor Latika Mennon’s first grad­uate stu­dent said he wanted to “change the world.” She knew of her exper­tise in making nanoporous alu­minum oxide and believed an anal­o­gous system with tita­nium dioxide, or titania, could be useful in the devel­op­ment of fuel cells and solar panels.

“Alu­minum is more like an insu­lator,” Menon explained. “For solar cells you need semi­con­duc­tors. Titania is a semiconductor.”

Using simple elec­tro­chem­ical methods, Menon’s team devel­oped a mate­rial made of neatly aligned, hollow, titania nan­otubes. “It’s an array of tubes,” she said. “Just like lots of cylin­ders, or test tubes, arranged in parallel.”

Menon explained that applying a voltage to a solu­tion of chlorine-containing salts causes a piece of sub­merged tita­nium foil to oxi­dize on the sur­face. Under cer­tain con­di­tions, the titania will morph into the highly aligned struc­ture she has described. “Since it’s a self-assembly process, we don’t have to worry about it, ” Menon said.

Physics professor Latika Menon studies titania nanotube arrays, shown here in cross section. Each circle depicts a separate nanotube. Unlike other nanotube systems, such as carbon, titania nanotubes arrange themselves into highly organized collections, like a box full of drinking straws, under particular electrochemical conditions. Latika Menon, Northeastern University

The method is straight­for­ward, cost effec­tive and, per­haps most impor­tantly, envi­ron­men­tally friendly. As such, Menon’s work dove­tails with Northeastern’s focus on con­ducting use-inspired research that solves global chal­lenges in health, secu­rity and sustainability.

Menon and her research team orig­i­nally designed the mate­rial to be used in alter­na­tive energy appli­ca­tions, but she has found that it could be used in a host of other applications.

Backed by a $50,000 grant from the Inno­va­tion Corps pro­gram of the National Sci­ence Foun­da­tion, she is cur­rently working to bring the tech­nology into a com­mer­cial setting.

Menon’s research team com­prises Moni­dipa Ghosh, a research assis­tant, and entre­pre­neurial mentor Prashanth Makaram, cofounder of the biotech startup Alpha Szen­szor, Inc., and a past member of pro­fessor Ahmed Busnaina’s lab in Northeastern’s Center for High Rate Nanoman­u­fac­turing.

Menon sug­gested that the technology’s tubular plat­form could be used as a filter, noting that its uni­form mor­phology makes it ideal for this par­tic­ular application.

According to Menon, the titania nan­otubes’ bio­com­pat­ible mate­rial makes it appealing for use in agri­cul­tural or cos­metics appli­ca­tions or as an alter­na­tive hydrogen gen­er­a­tion cat­a­lyst for fuel cells, which cur­rently use expen­sive plat­inum wires.

She also said that the nan­otubes can be easily removed from the foil sur­face as thin, cohe­sive sheets. This prop­erty could make the tech­nology useful for a variety of appli­ca­tions, including portable, flex­ible pho­to­voltaics and solar cells.

More­over, the color of these thin sheets is deter­mined by the diam­eter of the nan­otube. Since the dimen­sions can be con­trolled through tai­lored exper­i­mental con­di­tions, Menon’s team could con­ceiv­ably design pho­to­voltaic “paints” for the building and auto­mo­tive industries.