The ability to efficiently utilize solar thermal energy to enable liquid-to-vapor phase transition has great technological implications for a wide variety of applications, such as water treatment and chemical fractionation. Here, we demonstrate that functionalizing graphene using hydrophilic groups can greatly enhance the solar thermal steam generation efficiency. Our results show that specially functionalized graphene can improve the overall solar-to-vapor efficiency from 38% to 48% at one sun conditions compared to chemically reduced graphene oxide. Our experiments show that such an improvement is a surface effect mainly attributed to the more hydrophilic feature of functionalized graphene, which influences the water meniscus profile at the vapor-liquid interface due to capillary effect. This will lead to thinner water films close to the three-phase contact line, where the water surface temperature is higher since the resistance of thinner water film is smaller, leading to more efficient evaporation. This strategy of functionalizing graphene to make it more hydrophilic can be potentially integrated with the existing macroscopic heat isolation strategies to further improve the overall solar-to-vapor conversion efficiency.

The authors report the unusual thermal stability of deoxyribose nucleic acid (DNA) origami when adhered to a solid substrate. Even when heated to 150 °C for 45 min, these DNA nanostructures retain their physical and chemical integrity. This result suggests that DNA origami could be integrated into applications requiring moderate substrate heating, such as photoresist baking or chemical vapor deposition processes.

CONSPECTUS: Our work on lithographic patterning of DNA nanostructures was inspired by a collaboration on molecular electronic devices known as quantum-dot cellular automata or QCA. QCA is a paradigm for computation in which information is transmitted and processed through the interaction of coupled electrical charges or magnetic dipoles. We began to explore the idea of molecular scale QCA and found that ab initio methods, a thermodynamic Ising model, and larger scale circuit design work suggested that circuits that did computationally interesting things could function at room temperature if made from molecular QCA cells of chemically reasonable design. But how could the QCA cells be patterned to form the complex arrays needed for computationally interesting circuitry, and how could those arrays of molecular circuitry be integrated with conventional electronic inputs and outputs? Top-down methods lacked the spatial resolution and high level of parallelism needed to make molecular circuits. Bottom-up chemical synthesis lacked the ability to fabricate arbitrary and heterogeneous structures tens to hundreds of nanometers in size. Chemical self-assembly at the time could produce structures in the right size scale, but was limited to homogeneous arrays. A potential solution to this conundrum was just being demonstrated in the late 1990s and early 2000s: DNA nanostructures self-assembled from oligonucleotides, whose high information density could handle the creation of arbitrary structures and chemical inhomogeneity. Our group became interested in whether DNA nanostructures could function as self-assembling circuit boards for electrical or magnetic QCA systems. This Account focuses on what we learned about the interactions of DNA nanostructures with silicon substrates and, particularly, on how electron-beam lithography could be used to direct the binding of DNA nanostructures on a variety of functional substrates.

The designed nature and controlled, one-pot synthesis of DNA origami provides exciting opportunities in many fields, particularly nanoelectronics. Many of these applications require interaction with and adhesion of DNA nanostructures to a substrate. Due to its atomically flat and easily cleaned nature, mica has been the substrate of choice for DNA origami experiments. However, the practical applications of mica are relatively limited compared to those of semiconductor substrates. For this reason, a straightforward, stable, and repeatable process for DNA origami adhesion on derivatized silicon oxide is presented here. To promote the adhesion of DNA nanostructures to silicon oxide surface, a selfassembled monolayer of 3-aminopropyltriethoxysilane (APTES) is deposited from an aqueous solution that is compatible with many photoresists. The substrate must be cleaned of all organic and metal contaminants using Radio Corporation of America (RCA) cleaning processes and the native oxide layer must be etched to ensure a flat, functionalizable surface. Cleanrooms are equipped with facilities for silicon cleaning, however many components of DNA origami buffers and solutions are often not allowed in them due to contamination concerns. This manuscript describes the set-up and protocol for in-lab, small-scale silicon cleaning for researchers who do not have access to a cleanroom or would like to incorporate processes that could cause contamination of a cleanroom CMOS clean bench. Additionally, variables for regulating coverage are discussed and how to recognize and avoid common sample preparation problems is described. Video LinkThe video component of this article can be found at

When deoxyribose nucleic acid (DNA) origami on silicon substrates are heated above 900 °C, the carbon atoms from the DNA diffuse several nanometers into the silicon to form embedded silicon carbide (SiC) nanostructures. Atomic force microscopy and scanning electron microscopy images show that the SiC structures retain the shape and lateral dimensions of the original DNA origami structures, and the SiC material resists etching by hydrofluoric acid. X-ray photoelectron spectroscopy depth profiling shows a SiC peak present at depths of up to ∼15 nm. This process is a mask-free technique for patterning SiC on silicon for possible nanoelectronic applications.