Non‐Lithography Hydrodynamic Printing of Micro/Nanostructures on Curved Surfaces

A key issue of micro/nano devices is how to integrate micro/nanostructures with specified chemical components onto various curved surfaces. Hydrodynamic printing of micro/nanostructures on three‐dimensional curved surfaces is achieved with a strategy that combines template‐induced hydrodynamic printing and self‐assembly of nanoparticles (NPs). Non‐lithography flexible wall‐shaped templates are replicated with microscale features by dicing a trench‐shaped silicon wafer. Arising from the capillary pumped function between the template and curved substrates, NPs in the colloidal suspension self‐assemble into close‐packed micro/nanostructures without a gravity effect. Theoretical analysis with the lattice Boltzmann model reveals the fundamental principles of the hydrodynamic assembly process. Spiral linear structures achieved by two kinds of fluorescent NPs show non‐interfering photoluminescence properties, while the waveguide and photoluminescence are confirmed in 3D curved space. The printed multiconstituent micro/nanostructures with single‐NP resolution may serve as a general platform for optoelectronics beyond flat surfaces.     

Numerical study of the faithful replication of micro/nanostructures on curved surfaces by the electrohydrodynamic instability process

This paper reports the numerical study of the one‐step faithful replication of micro/nano‐scale structures on a fiber surface by using the electrohydrodynamic instability patterning (EHDIP) process. By employing a rigorous numerical analysis method, conditions are revealed under which the faithful replication of a pattern can be achieved from a curved master electrode. It is found that the radius of curvature of the fiber plays an important role in determining the final morphology of the pattern when the destabilizing electric field is dominant in both the flat and patterned template cases. In general, stronger electric fields and larger radii of curvature of the substrate are favorable for the faithful replication of the pattern. In addition, theoretical analysis shows that higher aspect ratio of micro/nanostructures can be obtained on curved surfaces by using a master with a much lower aspect ratio. The results demonstrated in this study aims to provide guidelines for the faithful fabrication of micro/nanostructures on curved surfaces by the EHDIP process.     

分子自组装法制备具有可控浸润性的铜表面简

通过简单浸泡的方法在铜基底上制备出了具有微纳米复合结构的氧化铜,再利用混合硫醇溶液[含HS(CH2)9CH3和 HS(CH2)11OH]对浸泡后的表面进行修饰,通过控制溶液中HS(CH2)11OH的浓度,制备出一系列具有不同浸润性的铜表面,实现表面从超疏水到超亲水的有效调控. 研究发现,表面浸润的可控性源于表面复合结构与不同化学组成的协同作用,微纳米复合结构的存在为表面浸润性的调节提供了必要的条件.     

分子自组装法制备具有可控浸润性的铜表面

通过简单浸泡的方法在铜基底上制备出了具有微纳米复合结构的氧化铜, 再利用混合硫醇溶液[含HS(CH₂)₉CH₃和 HS(CH₂)₁₁OH]对浸泡后的表面进行修饰, 通过控制溶液中HS(CH₂)₁₁OH的浓度, 制备出一系列具有不同浸润性的铜表面, 实现表面从超疏水到超亲水的有效调控. 研究发现, 表面浸润的可控性源于表面复合结构与不同化学组成的协同作用, 微纳米复合结构的存在为表面浸润性的调节提供了必要的条件.     

Controlled synthesis of responsive hydrogel nanostructures via microcontact printing and ATRP

Surfaces that are spatially functionalized with intelligent hydrogels, especially at the micro‐ and nanoscale, are of high interest in the diagnostic and therapeutic fields. Conventional methods of the semiconductor industry have been successfully employed for the patterning of hydrogels for various applications, but methods for fabricating precise 3 D patterns of hydrogels at the micro‐ and nanoscale over material surfaces remain limited. Herein, microcontact printing (µCP) followed by atom transfer radical polymerization (ATRP) was applied as a platform to synthesize temperature responsive poly(N‐isopropylacrylamide) hydrogels with varied network structures (e.g. different molecular weight crosslinkers) over gold surfaces. The XY control of the hydrogels was achieved using µCP, and the Z (thickness) control was achieved using ATRP. The controlled growth and the responsive behavior of hydrogels to temperature stimuli were characterized using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). The results demonstrate that this platform allows for the controlled growth of hydrogel nanostructures using the controlled ATRP mechanism. It is also shown that the molecular weight of the crosslinker affects the rate of hydrogel growth. These PNIPAAm‐based crosslinked hydrogel patterns were also demonstrated to have a temperature‐dependent swelling response. Using this technique, it is possible to synthesize responsive hydrogel patterns over various surfaces for potential applications in the biomedical field. Copyright © 2009 John Wiley & Sons, Ltd.     

Ag作催化剂制备的GaN的形貌及其性能

用化学气相沉积法(CVD)在Si(100)衬底上以Ag纳米颗粒为催化剂制备了微纳米结构的GaN,原料是熔融态的金属Ga和气态的NH3。采用X射线衍射仪(XRD)、透射电镜(TEM)、X-ray能谱仪(EDS)、场发射扫描电子显微镜(SEM)、光致发光能谱(PL)和霍尔效应测试对样品进行了结构、成分、形貌和发光、电学性能分析。结果表明:生成的自组装GaN为六方纤锌矿的类似小梯子的微纳米单晶结构,且在不同的温度下,GaN的发光性能和电学性能也有所不同,相对于强的紫外发光峰,其它杂质发光峰很微弱,且均呈p型导电。对本实验所得到的GaN微纳米结构的可能形成机理进行了探讨。     

Amplified surface plasmon resonance based DNA biosensors, aptasensors, and Hg2+ sensors using hemin/G-quadruplexes and Au nanoparticles

Thiolated nucleic acid hairpin nanostructures that include in their stem region a "caged" G-quadruplex sequence, and in their single-stranded loop region oligonucleotide recognition sequences for DNA, adenosine monophosphate (AMP), or Hg(2+) ions were linked to bare Au surfaces or to Au nanoparticles (NPs) linked to Au surfaces. The opening of the hairpin nanostructures associated with the bare Au surface by the complementary target DNA, AMP substrate, or Hg(2+) ions, in the presence of hemin, led to the self-assembly of hemin/G-quadruplexes on the surface. The resulting dielectric changes on the surface exhibited shifts in the surface plasmon resonance (SPR) spectra, thus providing a readout signal for the recognition events. A similar opening of the hairpin nanostructures, immobilized on the Au NPs associated with the Au surface, by the DNA, AMP, or Hg(2+) led to an ultrasensitive SPR-amplified detection of the respective analytes. The amplification originated from the coupling between the localized surface plasmon associated with the NPs and the surface plasmon wave, an effect that cooperatively amplifies the SPR shifts that result from the formation of the hemin/G-quadruplexes. The different sensing platforms reveal impressive sensitivities and selectivities toward the target analytes.     

Fine tuning photoluminescence properties of CdSe nanoparticles by surface states modulation

Fine control of the photoluminescence properties of CdSe nanoparticles (NPs) dispersed in CHCl3 is achieved by simple adjustment of the NPs concentration, and the wavelength of photoluminescence emission of CdSe NPs can be tuned within the nanometer accuracy. The mechanism of the process is proposed to be relevant to the modulation of the surface states of NPs by the concentration. This solution-based approach offers an attractive and complementary process to the conventional band gap engineering of semiconductor NPs with fine tunable optical properties.     

A massively parallel electrochemical approach to the miniaturization of organic micro- and nanostructures on surfaces

This paper describes a simple and convenient strategy for reducing the dimensions of organic micro-and nanostructures on metal surfaces. By varying electrochemical desorption conditions, features patterned by dip-pen nanolithography or micro contact printing and made of linear alkanethiols or selenols can be gradually desorbed in a controlled fashion. The process is referred to as electrochemical whittling because the adsorbate desorption is initiated at the exterior of the feature and moves inward as a function of time. The whittling process and adsorbate desorption were studied as a function of substrate morphology, adsorbate head and tail groups, and electrolyte solvent and salt. Importantly, one can independently address different nanostructures made of different adsorbates and effect their miniaturization based upon ajudicious selection of adsorbate, applied potential, and supporting electrolyte. Some of the physical and chemical origins of these observations have been elucidated.     

Ostwald‐Ripening‐Induced Growth of Parallel Face‐Exposed Ag Nanoplates on Micro‐Hemispheres for High SERS Activity

Ag nanoplates, as two‐dimensional plasmonic nanostructures, have attracted intensive attention due to their strong shape‐dependent optical properties and related applications. Here parallel face‐exposed Ag nanoplates vertically grown on micro‐hemisphere surfaces have been achieved by firstly electrodepositing the micro‐hemispheres assembled by Ag nanoplates, whose planar surfaces are stuck together, on indium tin oxide substrates, and then Ostwald ripening the as‐electrodeposited micro‐hemispheres in water. The sizes of the nanoplates and the gaps between the neighboring nanoplates have been tailored by tuning the Ostwald‐ripening duration, so that the SERS activity of the micro‐hemispheres has been remarkably improved. The improved SERS activity can be well explained by our systematic finite‐element simulation. Therefore, Ostwald ripening offers a route to the synthesis of Ag nanoplates, and the optimization of plasmon coupling and SERS activity of nanostructure‐assembled systems.     

Drop impact characteristics and structure effects of hydrophobic surfaces with micro- and/or nanoscaled structures

We report the drop impact characteristics on four hydrophobic surfaces with different well-scale structures (smooth, nano, micro, and hierarchical micro/nano) and the effects of those structures on the behavior of water drops during impact. The specimens were fabricated using silicon wet etching, black silicon formation, or the combination of these methods. On the surfaces, the microstructures form obstacles to drop spreading and retracting, the nanostructures give extreme water-repellency, and the hierarchical micro/nanostructures facilitate drop fragmentation. The maximum spreading factor (D*(max)) differed among the structures. On the basis of published models of D*(max), we interpret the results of our experiment and suggest reasonable explanations for these differences. Especially, the micro/nanostructures caused instability of the interface between liquid and air at Weber number We > ~80 and impacting drops fragmented at We > ~150.     

Assessing the synergy effect of additive and matrix on single-crystal growth: Morphological revolution resulted from gel-mediated enhancement on CIT-calcite interaction

CIT additives are active in crystal morphology modification at relatively high concentration. Once agarose gel is simultaneously introduced, the curved morphological feature of calcite crystal emerges at a much lower concentration of CIT additives.     

Au@ZIF-8核壳结构中金纳米粒子分布的调控及其在荧光分子光致发光传感中的应用

控制金属@MOF核壳纳米结构中金属纳米粒子的分布不容易实现。我们应用了合成MOF胶体粒子所用到的配位调制方法来合成Au@ZIF-8核壳纳米结构。通过使用过量的2-甲基咪唑和不同用量的1-甲基咪唑可获得不同的Au@ZIF-8。该合成方法可在ZIF-8纳米晶体中灵活调整Au纳米粒子（Au NPs）的分布。此外,我们分别研究了2种不同尺寸的荧光分子与Au@ZIF-8结合后的光致发光光谱和寿命。ZIF-8的孔径可以决定这2种分子是否可通过多孔壳结构接近Au NPs。分子光学特性对Au NPs近场的发光增强和荧光猝灭的竞争非常敏感。     

A novel route to obtain metal and oxide nanoparticles co-existing on a substrate

In this work we present a novel route to cover large surfaces with metal and oxide nanoparticles (NPs) by growing and annealing of metallic bilayers. We have used this method to fabricate ensembles of Au and α-Fe₂O₃ NPs on silica substrates from Fe/Au bilayers. The morphology of the hybrid nanostructures and the presence of defects and disorder can be tuned through the processing parameters as the initial film thickness and the annealing conditions. The proximity effects between both types of NPs alter their physical properties. In particular, we observe that the presence of α-Fe₂O₃ NPs modifies the surface plasmon resonance of Au NPs.     

Synthesis, photoluminescence, and adsorption of CdS/dendrimer nanocomposites

CdS/dendrimer nanocomposites can be synthesized from methanolic Cd(2+) and S(2-) with amine-terminated polyamidoamine dendrimers of generation 8 (G8NH(2)) as stabilizers. By controlling the preparation conditions, nanoparticles with diameters < or = 2 nm can be obtained with a narrow size distribution. They show blue photoluminescence at approximately 450 nm. We studied the effects of various additives on the photoluminescence and elucidated its mechanism. Stable aggregates of two to three G8NH(2) molecules with several CdS nanoparticles form; the particles are located at the surface of the G8NH(2) molecules. The adsorption of the CdS/G8NH(2) nanocomposites on flat substrate surfaces is determined by the substrate chemistry. The hydrophilic nature of G8NH(2) results in weak affinity to graphite but strong affinity to hydroxy-terminated substrates such as mica, oxidized silicon wafers, and carboxylate-terminated monolayers. Patterning of nanocomposites on these hydrophilic substrates is achieved by the microcontact printing method. We propose to use only one molecule, a large dendrimer, to control the nanoparticle formation and also the immobilization of the synthesized nanoparticle/dendrimer composites.     

Peristome‐Mimetic Curved Surface for Spontaneous and Directional Separation of Micro Water‐in‐Oil Drops

Separation of micro‐scaled water‐in‐oil droplets is important in environmental protection, bioassays, and saving functional inks. So far, bulk oil–water separation has been achieved by membrane separation and sponge absorption, but micro‐drop separation still remains a challenge. Herein we report that instead of the “plug‐and‐go” separation model, tiny water‐in‐oil droplets can be separated into pure water and oil droplets through “go‐in‐opposite ways” on curved peristome‐mimetic surfaces, in milliseconds, without energy input. More importantly, this overflow controlled method can be applied to handle oil‐in‐oil droplets with surface tension differences as low as 14.7 mN m⁻¹ and viscous liquids with viscosities as high as hundreds centipoises, which markedly increases the range of applicable liquids for micro‐scaled separation. Furthermore, the curved peristome‐mimetic surface guides the separated drops in different directions with high efficiency.     

聚合物基微纳米功能复合材料3D打印加工的研究

高分子材料3D打印加工可制备传统加工不能制备的形状复杂的高分子制件,是近年来发展很快的先进制造技术。但适用于3D打印加工的高分子材料种类少,结构功能单一,难以制备高分子功能器件。本文介绍了我们在聚合物基微纳米功能复合材料3D打印加工方面的研究工作:通过有机/无机杂化、固相剪切碾磨、超声辐照、分子复合等技术制备适合于选择性激光烧结(SLS)和熔融沉积成型(FDM)的聚合物基微纳米功能复合材料;实现了聚合物基微纳米功能复合粉体的SLS加工和功能复合丝条的FDM加工;研究了3D打印低维构建、层层叠加、自由界面成型、复杂固-液-固转变过程;建立了功能复合粉体球形化技术,发明了直接熔融挤出新型FDM打印机;制备了常规加工方法不能制备的数种形状复杂的功能器件,如尼龙11/钛酸钡压电器件、柔性聚氨酯/碳纳米管传感器、个性化人颌骨模型等,突破了传统加工难以制备复杂形状制品和目前3D打印难以制备功能制品的局限。     

Bioinspired synthesis and preparation of multilevel micro/nanostructured materials

In this review, some living organisms with multilevel hierarchical micro/nanostructures and related special properties are briefly introduced. The unique properties of organisms are mostly related to their special hierarchical micro/nanostructures. Inspired by nature, many zero-dimensional and one-dimensional micro/nanomaterials with biomimic or bioinspired multilevel micro/nanostructures have been successfully synthesized and prepared in recent years. Compared with traditional solid materials, the synthesis and preparation of these multilevel structured materials is more ingenious. Moreover, these kinds of multilevel micro/nanomaterials show fantastic properties in many fields because of their micro/nanoscale complex interior structures, whichmay be intended for application in catalysis, Li-ion batteries, biomedicines, sensors, and others.     

Facile synthesis of concave decahedra enclosed by high-index facets and truncated decahedra with a large size

Nanostructures with concave surfaces are not common, and their synthesis is still challenging. In this paper, we have successfully synthesized two kinds of five-fold-twinned Au decahedra and dodecagonal plates by changing the reaction conditions. 40 high-index {221} facets were observed in the concave decahedron. The truncated decahedral gold nanocrystals (NCs) with a large size of 250-350 nm were obtained for the first time, which breaks the assumption that the truncated five-fold-twinned Au nanoparticles (NPs) can only be obtained with a size below 5 nm. The growth mechanism and the evolution process of the gold nanostructures were discussed. This work provides a facile way to synthesize concave decahedra, truncated decahedra and dodecagonal plates with controlled nanostructures.     

Coordination-based gold nanoparticle layers

Gold nanoparticle (NP) mono- and multilayers were constructed on gold surfaces using coordination chemistry. Hydrophilic Au NPs (6.4 nm average core diameter), capped with a monolayer of 6-mercaptohexanol, were modified by partial substitution of bishydroxamic acid disulfide ligand molecules into their capping layer. A monolayer of the ligand-modified Au NPs was assembled via coordination with Zr4+ ions onto a semitransparent Au substrate (15 nm Au, evaporated on silanized glass and annealed) precoated with a self-assembled monolayer of the bishydroxamate disulfide ligand. Layer-by-layer construction of NP multilayers was achieved by alternate binding of Zr4+ ions and ligand-modified NPs onto the first NP layer. Characterization by atomic force microscopy (AFM), ellipsometry, wettability, transmission UV-vis spectroscopy, and cross-sectional transmission electron microscopy showed regular growth of NP layers, with a similar NP density in successive layers and gradually increased roughness. The use of coordination chemistry enables convenient step-by-step assembly of different ligand-possessing components to obtain elaborate structures. This is demonstrated by introducing nanometer-scale vertical spacing between a NP layer and the gold surface, using a coordination-based organic multilayer. Electrical characterization of the NP films was carried out using conductive AFM, emphasizing the barrier properties of the organic spacer multilayer. The results exhibit the potential of coordination self-assembly in achieving highly controlled composite nanostructures comprising molecules, NPs, and other ligand-derivatized components.