DNA lithography
DNA origami shaped metal nanoparticles
Alexander Dubov, N+1
Scientists have combined the DNA origami approach with traditional nanolithography and developed a method for obtaining metal nanoparticles of a given shape with nanometer resolution. The shape of the particles corresponds to the shape of the DNA structures used as templates and allows them to be used, for example, as elements of optical sensors, scientists write in Science Advances (Shen et al., Plasmonic nanostructures through DNA-assisted lithography).
Over the past few years, DNA origami techniques have been developing at a really fast pace. The approach developed a little more than 10 years ago, based on the use of complementary bonds between nitrogenous bases, already makes it possible to obtain three-dimensional structures of a sufficiently large size (including from a single molecule), or two-dimensional micron arrays of nanometer resolution with functional particles sewn in specified places. Nevertheless, quite a few really useful applications for the DNA origami method have been proposed so far.
One of the possible ways of useful application of DNA origami right now is to use the shape of DNA structures as a template for nanoparticles of a different composition, for example, from metal and semiconductor. This is the approach used by scientists from Finland, the USA and Denmark under the leadership of Jussi Toppari (J. Jussi Toppari) from By combining DNA origami with traditional lithographic methods, so that metal particles of the desired shape can be obtained.
A folded DNA molecule of a clearly defined shape in the proposed approach was used as a template, which was first applied to the silicon surface, and then set the shape of an additional layer, which served as a mask for metal deposition. In total, the proposed lithographic method included eight stages of deposition of films of various compositions, dissolution, chemical and ion etching. As a result of all these stages, scientists obtained metal particles (from gold or an alloy of gold and palladium) of the desired shape on an inert substrate (quartz or silicon nitride).
Scientists called the proposed technique DNA-assisted lithography (DALI) and were able to obtain several metal structures of a given shape using it. In total, the authors of the work used three different types of folded DNA molecules: in the form of a cross, a bow tie or in the shape of the letter Z. The shape of the particles was chosen based on their possible further use for optical applications using plasmon resonance. For example, gold nanoparticles in the form of a butterfly (with a nanometer gap between the two halves) can be used as plasmon antennas receiving a signal in the visible range, and elements of biosensors can be made from chiral Z-shaped particles to determine optically active molecules.
The researchers note that since metal particles of the desired shape can be obtained on transparent substrates using the proposed method, the use of the developed lithographic technique is extremely promising for obtaining plasmon optical devices, as well as metamaterials consisting of nanoparticles about 10 nanometers in size. At the same time, most of the forms of metal particles that can be obtained using the proposed method are not available for obtaining by traditional methods, in particular, approaches based on "wet chemistry". It is especially possible to win in this way in the accuracy of setting the shape of the final structure. DNA can be used for lithographic methods of obtaining nanostructures consisting of metal particles not only as templates, but also, for example, for connecting particles to each other and constructing ordered arrays from them. Recently, American scientists have proposed using such a method to create superlattices consisting of gold nanoparticles of various shapes.
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