Nanoparticle patterning: High‐Resolution,Parallel Patterning of Nanoparticles via an Ion‐Induced Focusing Mask (Small 19/2010)

An ion‐induced focusing mask under the simultaneous injection of ions and charged aerosols generates invisible electrostatic lenses around each opening, through which charged nanoparticles are convergently guided without depositing on the mask surface. The sizes of the created features become significantly smaller than those of the mask openings due to the focusing capability. It is not only demonstrated that material‐independent nanoparticles including proteins can be patterned as an ordered array on any surface regardless of the conductive, nonconductive, or flexible nature of the substrate, but also that the array density can be increased. Highly sensitive gas sensors based on these focused nanoparticle patterns are fabricated via the concept.     

Sniffing the Unique “Odor Print” of Non‐Small‐Cell Lung Cancer with Gold Nanoparticles

A highly sensitive and fast‐response array of sensors based on gold nanoparticles, in combination with pattern recognition methods, can distinguish between the odor prints of non‐small‐cell lung cancer and negative controls with 100% accuracy, with no need for preconcentration techniques. Additionally, preliminary results indicate that the same array of sensors might serve as a better tool for understanding the biochemical source of volatile organic compounds that might occur in cancer cells and appear in the exhaled breath, as compared to traditional spectrometry techniques. The reported results provide a launching pad to initiate a bedside tool that might be able to screen for early stages of lung cancer and allow higher cure rates. In addition, such a tool might be used for the immediate diagnosis of fresh (frozen) tissues of lung cancer in operating rooms, where a dichotomic diagnosis is crucial to guide surgeons.     

“Snowing” Graphene using Microwave Ovens

Developing a simple and industrially scalable method to produce graphene with high quality and low cost will determine graphene's future. The two conventional approaches, chemical vapor deposition and liquid‐phase exfoliation, require either costly substrates with limited production rate or complicated post treatment with limited quality, astricting their development. Herein, an extremely simple process is presented for synthesizing high quality graphene at low‐cost in the gas phase, similar to “snowing,” which is catalyst‐free, substrate‐free, and scalable. This is achieved by utilizing corona discharge of SiO₂/Si in an ordinary household microwave oven at ambient pressure. High quality graphene flakes can “snow” on any substrate, with thin‐flakes even down to the monolayer. In particular, a high yield of ≈6.28% or a rate of up to ≈0.11 g h^?1 can be achieved in a conventional microwave oven. It is demonstrated that the snowing process produces foam‐like, fluffy, 3D macroscopic architectures, which are further used in strain sensors for achieving high sensitivity (average gauge factor ≈ 171.06) and large workable strain range (0%–110%) simultaneously. It is foreseen that this facile and scalable strategy can be extended for “snowing” other functional 2D materials, benefiting their low‐cost production and wide applications.     

Meso‐Reconstruction of Wool Keratin 3D “Molecular Springs” for Tunable Ultra‐Sensitive and Highly Recovery Strain Sensors

Wool keratin (WK) consists of a large number of α‐helices, which are just like many molecular‐scale springs. Herein, the construction of 3D WK molecular spring networks are reported by cross‐linking individual WK molecules via a Michael addition reaction. The as‐prepared springs display a superior recovery capability with unusual nonlinear elasticity, very low dissipative energy, and turntable elastic constant achieved by adjusting the chemical crosslinking density of WK networks. Owing to these unique characteristics, the 3D WK networks based flexible strain sensors reveal a high sensitivity, broad sensing ranges, and extremely long and stable performance. While normal highly sensible strain sensors, obtained by highly sophisticated surface or bulk patterning, often exhibit a relatively narrow range of measurements and limited life cycles. Such the WK mediated sensing materials have widespread applications in wearable electronics, such as detection and tracking of different human motions, and even discern voice during speaking.     

Highly Surface‐roughened “Flower‐like” Silver Nanoparticles for Extremely Sensitive Substrates of Surface‐enhanced Raman Scattering

Surface‐enhanced Raman scattering (SERS) is a new optical spectroscopic analysis technique with potential for highly sensitive detection of molecules. Recently, many efforts have been made to find SERS substrates with high sensitivity and reproducibility. In this Research News article, we provide a focused review on the synthesis of monodispersed silver particles with a novel, highly roughened, “flower‐like” morphology by reducing silver nitrate with ascorbic acid in aqueous solutions. The nanometer‐scale surface roughness of the particles can provide several hot spots on a single particle, which significantly increases SERS enhancement. The incident polarization‐dependent SERS of individual particles is also studied. Although the different “hot spots” on a single particle can have a strong polarization dependency, the total Raman signals from an individual particle usually have no obvious polarization dependency. Moreover, these flower‐like silver particles can be measured by SERS with high enhancement several times, which indicates the high stability of the hot spots. Hence, the flower‐like silver particles here can serve as highly sensitive and reproducible SERS substrates.     

Self‐Assembled “Breathing” Grana‐Like Cisternae Stacks

Membranes in cells display elaborate, dynamic morphologies intimately tied to defined cellular functions. Cisternae stacks are a common membrane morphology in cells widely found in organelles. However, compared with the well‐studied spherical cell membrane mimics, cisternae stacks as organelle membrane mimics are greatly neglected because of the difficulty of fabricating this unique structure. Herein, the grana‐like cisternae stacks are assembled via the reorganization of stacked microsized bicelles to mimic grana functions. The cisternae stacks are connected by fusion regions between adjacent cisternae. The number of cisternae can be controlled from ≈4 to 15 by the variation of ethanol volume percentage. Under the stimulation of solvent or negatively charged nanoparticles, the cisternae stacks can reversibly compress and expand, similar to the “breathing” property of natural grana. During the “breathing” process, nanoparticles are reversibly captured and released. Frequency resonance energy transfer is realized on the cisternae stacks trapped with two kinds of quantum dots. The cisternae stacks provide advanced membrane model for cell biotechnology, and clues for the shaping of organelles composed of cisternae. The ability of the cisternae stacks to capture materials enables them to possibly be applied in biomimetics and the design of advanced functional materials.