Herein, we report a facile and robust route to nanoscale tunable triboelectric energy harvesters realized by the formation of highly functional and controllable nanostructures via block copolymer (BCP) self-assembly. Our strategy is based on the incorporation of various silica nanostructures derived from the self-assembly of BCPs to enhance the characteristics of triboelectric nanogenerators (TENGs) by modulating the contact-surface area and the frictional force. Our simulation data also confirm that the nanoarchitectured morphologies are effective for triboelectric generation.

Nanotransfer printing technology offers outstanding simplicity and throughput in the fabrication of transistors, metamaterials, epidermal sensors and other emerging devices. Nevertheless, the development of a large-area sub-50 nm nanotransfer printing process has been hindered by fundamental reliability issues in the replication of high-resolution templates and in the release of generated nanostructures. Here we present a solvent-assisted nanotransfer printing technique based on high-fidelity replication of sub-20 nm patterns using a dual-functional bilayer polymer thin film. For uniform and fast release of nanostructures on diverse receiver surfaces, interface-specific adhesion control is realized by employing a polydimethylsiloxane gel pad as a solvent-emitting transfer medium, providing unusual printing capability even on biological surfaces such as human skin and fruit peels. Based on this principle, we also demonstrate reliable printing of high-density metallic nanostructures for non-destructive and rapid surface-enhanced Raman spectroscopy analyses and for hydrogen detection sensors with excellent responsiveness.

Although magnesiothermic reduction has attracted immense attention as a facile route for the fabrication of mass-scale Si nanostructures for highcapacity lithium-ion battery applications, its low conversion yield (<50%) and the discovery of a sustainable and low-cost precursor remain challenging. Here, an unprecedentedly high fi nal conversion yield (>98%) of magnesiothermic reduction based on control of reaction pressure is reported. The successful use of sand as a nearly infi nite and extremely low-cost source for the high-yield fabrication of nanostructured Si electrodes for Li-ion batteries is demonstrated. On the basis of a step-by-step analysis of the material's structural, morphological, and compositional changes, a two-step conversion reaction mechanism is proposed that can clearly explain the phase behavior and the high conversion yield. The excellent charge-discharge performance (specifi c capacities over 1500 mAh g −1 for 100 cycles) of the hierarchical Si nanostructure suggests that this facile, fast, and high-effi ciency synthesis strategy from ultralow-cost sand particles provides outstanding cost-effectiveness and possible scalability for the commercialization of Si electrodes for energy-storage applications.

The directed self-assembly (DSA) of block copolymers (BCPs) has been suggested as a promising nanofabrication solution. However, further improvements of both the pattern quality and manufacturability remain as critical challenges. Although the use of BCPs with a high Flory-Huggins interaction parameter ( χ ) has been suggested as a potential solution, this practical self-assembly route has yet to be developed due to their extremely slow selfassembly kinetics. In this study, it is reported that warm solvent annealing (WSA) in a controlled environment can markedly improve both the selfassembly kinetics and pattern quality. A means of avoiding the undesirable trade-off between the quality and formation throughput of the self-assembled patterns, which is a dilemma which arises when using the conventional solvent vapor treatment, is suggested. As a demonstration, the formation of well-defi ned 13-nm-wide self-assembled patterns (3σ line edge roughness of ≈2.50 nm) in treatment times of 0.5 min (for 360-nm-wide templates) is shown. Self-consistent fi eld theory (SCFT) simulation results are provided to elucidate the mechanism of the pattern quality improvement realized by WSA.

The discovery of the surface-enhanced Raman scattering (SERS) effect provided a revolutionary solution to the issue of low sensitivity in Raman spectroscopy. For more widespread application of SERS analysis, however, practical fabrication of well-defined ultrasmall nanostructures having large SERS signal enhancement capability and large-area signal uniformity is still a major challenge. Here, we report that rings-in-mesh Au nanostructures, which can be obtained by the consecutive self-assembly of polystyrene nanospheres and block copolymers (BCPs) with far different length scales, provide multiple advantages for SERS analysis in terms of signal amplification and measurement reproducibility. Significant signal enhancement is achieved by the hierarchical geometry composed of a submicrometer nanomesh and sub-10-nm nanogaps, which can be obtained from the self-assembly phenomena of polystyrene nanospheres and siloxane-based BCPs, respectively. Moreover, the two-dimensionally isotropic characteristics of the concentric nanoring structures eliminate the angular dependence of the SERS signal intensity and provide excellent reproducibility of measurement over a large area. ■ INTRODUCTIONRaman spectroscopy provides many advantages, such as high accuracy, high speed, and nondestructiveness for the characterization of a wide range of materials. However, despite these outstanding characteristics, 1−5 Raman spectroscopy fails to offer sufficient detection sensitivity, because of its weak signal intensity. 6 Surface-enhanced Raman scattering (SERS) is considered the most successful strategy for significantly enhancing the scattering cross-section and, consequently, the signal intensity. 7 The Raman intensity on noble metals such as gold and silver can be increased by several orders of magnitude by local enhancement of the electromagnetic field, 8−15 which can be controlled by the size, shape, and distance of metal nanostructures. Various metallic nanostructures such as nanoparticles, 6,16−18 nanogaps, 19−25 and sharp tips 26−28 have been suggested for maximizing the SERS signal intensity. Although previous studies reported a huge enhancement factor by controlling the size and arrangement of such nanostructures, facile and controlled creation of sub-10-nm plasmonic nanostructures with ultrahigh density, high throughput, and large-area uniformity remains a considerable challenge. 29−33 Moreover, the synergic combination of plasmonic nanostructures for maximizing signal intensity is not straightforward, because of process complexity.Compared to top-down photolithographic methods, selforganization of macromolecular materials is a promising fabrication route for well-controlled and well-ordered nanostructures with large-area uniformity, because of its high throughput, cost-effectiveness, and scalability. 21,32,34−38 In particular, the self-assembly of block copolymers (BCPs) is one of the most attractive candidates, because of the ability of BCPs to spontaneously assemble into a variety of structures at the nanometer length scale....

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The fabrication and characterization of nanoscale hole arrays (NHA) have been extensively performed for a variety of unique characteristics including extraordinary optical transmission phenomenon observed for plasmonic NHAs. Although the size miniaturization and hole densification are strongly required for enhancement of high-frequency optical responses, from a practical point-of-view, it is still not straightforward to manufacture NHA using conventional lithography techniques. Herein, a facile, cost-effective, and transferrable fabrication route for high-resolution and high-density NHA with sub-50 nm periodicity is demonstrated. Solvent-assisted nanotransfer printing with ultrahigh-resolution combined with block copolymer self-assembly is used to fabricate well-defined Si nanomesh master template with 4-fold symmetry. An Au NHA film on quartz substrate is then obtained by thermal-evaporation on the Si master and subsequent transfer of the sample, resulting in NHA structure having a hole with a diameter of 18 nm and a density over 400 holes/μm. A resonance peak at the wavelength of 650 nm, which is not present in the transmittance spectrum of a flat Au film, is observed for the Au NHA film. Finite-difference time-domain (FDTD) simulation results propose that the unexpected peak appears because of plasmonic surface guiding mode. The position of the resonance peak shows the sensitivity toward the change of the refractive index of surrounding medium, suggesting it as a promising label-free sensor application. In addition, other types of Au nanostructure arrays such as geometry-controlled NHA and nanoparticle arrays (NPAs) shows the outstanding versatility of our approach.

Although precisely controlled microdomains of block copolymers (BCP) provide an excellent guiding matrix for multiple nanoparticles (NPs) to be controllably segregated into a desired polymer block, localization and positioning of individual NPs have not been demonstrated. Here, we report a unique one-to-one positioning phenomenon of guest Au NPs in the host BCP microdomains; each of polystyrene-functionalized Au NPs is embedded within the perforation domain of hexagonally perforated lamellar (HPL) morphology of poly­(dimethyl­siloxane-b-styrene) BCP. The local minimization of free energy achieved by the placement of Au NPs into the center of the perforation domain is theoretically supported by the self-consistent field theory (SCFT) simulation. We propose a novel design principle for more precisely controllable nanocomposites by developing a new route of NP arrangement within a polymer matrix.