Fabrication of a NCD microelectrode array for amperometric detection with micrometer spatial resolution

We report on the fabrication of a boron-doped nanocrystalline diamond (NCD) 3 × 3 high-density microelectrode array (MEA) for amperometric measurements, with a single electrode area of 3 × 5 μm² and a separation in the μm scale. The NCD microelectrodes were grown by hot filament chemical vapor deposition (HFCVD) on a double-side polished sapphire wafer in order to preserve the diamond transparency. Bias enhanced nucleation (BEN) was performed to ensure a covalent adhesion of the films to the substrate. A current background noise of less than 5 pA peak to peak over a 1 kHz bandwidth resulted from an electrochemical investigation of the new device, using 100 mM KCl solutions and ferrocyanide red-ox couples. Cyclic voltammetry measurements in physiological buffer solution and in the presence of oxidizable bio-molecules strengthened its suitability for bio-sensing. When compared to a 2 × 2 NCD microelectrode array prototype, already used for in vitro cell measurements, the signal to noise ratio of the amperometric response of the new 3 × 3 device proved twice as good. In addition, the optical transmittance of the boron-doped thin layers exceeded 40% in the visible wavelength range.The excellent electrochemical properties of NCD electrodes and the transparency in combination with the high spatial resolution make the new 3 × 3 NCD MEA a promising tool for electrochemical sensing in a variety of applications, ranging from medical to industrial, in neutral or harsh environments.     

Restacking-inhibited nitrogen-incorporated mesoporous reduced graphene oxides for high energy supercapacitors

Graphene is considered a promising active electrode material due to a large surface area, high electronic conductivity, and chemical and mechanical stabilities for supercapacitor (SC) applications. However, the current bottleneck is the fabrication of restacking-inhibited graphene on an electrode level which otherwise loses the capability to achieve the aforementioned properties. Herein, we demonstrate the synthesis of restacking-inhibited nitrogen (N)-incorporated mesoporous graphene for high energy SCs. The melamine-formaldehyde acts as a restacking inhibitor by forming a bonding with reduced graphene oxide (RGO) through a condensation reaction and as an N precursor to be decomposed to create open pores and N sources upon heat treatment. The d-spacing increases up to 0.352 nm and the surface area is as high as 698 m² g^?1 with high mesoporosity, confirming restacking inhibition by N incorporation decomposed by melamine-formaldehyde. The restacking-inhibited RGO-based SC cells in organic electrolyte show the specific capacitance of 25.8 F g^?1, the energy density of 21.8 kW kg^?1 and 85% of capacitance retention for 5000 cycles, which are better than those of pristine RGO-based cells. These improved SC performances are attributed to the fast ion transport through a mesoporous channel in crumpled structure and the doping effect of N incorporation. This work provides a simple yet effective chemical approach to fabricate restacking-inhibited RGO electrodes for improved SC performances.     

Fabrication of nickel oxide-embedded titania nanotube array for redox capacitance application

Titania nanotube array with an enlarged tube diameter of 110 nm and length of 700 nm was grown on titanium metal by a potentiostatic anodization in hydrofluoric acid-phosphoric acid-ethenyl glycol electrolyte. Nickel hydroxide was introduced into this titania nanotubes by either an electrodeposition-oxidation or hydrothermal process. Nickel oxide-titania composite was finally formed by heating treatment at 300 °C. Such a well-defined nanocomposite supported on titanium substrate was designed as a functional nanotube array electrode for the redox capacitance application. The morphology, microstructure and electrochemical properties of the nanocomposites were investigated by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray diffraction and cyclic voltammetry measurements. It was found that nickel oxide could be embedded in titania nanotubes and extend from inner wall to top layer with an open pore mouth. The entire tube lengths were approx. 770 nm and 710 nm, meanwhile nickel-to-titanium atom ratios were determined as 9.6 at% and 36.4 at% for nickel oxide-embedded titania by an electrochemical and hydrothermal synthesis, respectively. The corresponding specific redox capacitance was also increased from 26 mF cm⁻² to 85 mF cm⁻² with highly reversible charge-discharge stability. Such an improvement was mostly ascribed to more accessible reaction interface of electroactive nickel oxide through its higher loading and a uniform dispersion on titania nanotubes. The capacitance was further increased up to 128 mF cm⁻² for 36.4 at% nickel-containing nickel oxide-titania/titanium electrode when a porous graphite carbon instead of a platinum sheet was used as a cathode.     

Fabrication and electrochemical properties of carbon nanotube array electrode for supercapacitors

The multiwalled carbon nanotube (MWNT) array was fabricated by chemical vapor deposition (CVD) in the template of porous alumina from the carbonaceous source of C₂H₂ in the presence of a catalyst of ferric metals. To utilize the external surface other than the inner surface of the carbon nanotubes, 1 mol/L sulfuric acid was applied to remove off the most part of AAO template on the carbon nanotube electrode. The electrochemical performances of the carbon nanotube array electrode were investigated by use of the cyclic voltammetry, galvanostatic charge/discharge and ac impedance methods for its application in supercapacitors. The specific capacitance of 365 F/g of the electrode was achieved with the discharge current density of 210 mA/g in the solution of 1 mol/L H₂SO₄. In addition, the carbon nanotube array electrode was found to have low equivalent series resistance (ESR) and good cycling stability.     

含氮杂原子B-Beta分子筛的制备及其对Knoevenagel缩合反应的催化性能

水热合成杂原子B-Beta分子筛,低温氮化二次处理制备N掺杂的新型碱催化剂,利用Knoevenagel缩合反应进行碱性催化性能评价,考察氮化温度、反应时间、不同氮化前驱体及催化剂稳定性对反应的影响.结果表明,采用低温500℃氮化处理的杂原子B-Beta分子筛催化剂具有优异的催化活性,苯甲醛转化率及产物选择性均接近100...     

Protein-modified nanodiamond particles for Layer-by-Layer assembly

Nanodiamond (ND) particles were modified by protein bovine serum albumin (BSA) through chemical method. The immobilization of BSA onto ND surface was demonstrated by FT-IR and UV-Vis spectroscopies. The NDBSA particle size was stable at ca. 470 nm over the pH range of 4.5-7.5 by virtue of strong ND-BSA interaction but increased rapidly to ca. 600 nm when pH was higher than 7.5 or lower than 4.5 due to BSA conformational changes, indicating that the as-prepared NDBSA was able to self-assemble in solution. Based on the strong ND-protein interactions, NDBSA/ND coatings were then deposited onto glass substrate through Layer-by-Layer (LBL) assembly process. The growth of NDBSA/ND coating by LBL assembly was evidenced by UV-Vis absorption spectra. The NDBSA/ND coating possessed a denser structure with less interconnected pores as more bilayers of coatings were deposited onto the glass substrate, showing that more densely-organized coating structures could be obtained by increasing the number of bilayers deposited. This work suggests that ND-based films by LBL method could be promising candidates for biomolecule immobilizations, which has great potentials to be applied to the field of biosensors.     

PEGylated nanodiamond for chemotherapeutic drug delivery

Nanodiamond (ND) has the excellent biocompatibility, similarly to other sp³-carbon based materials, and is a potential drug carrier for cancer therapy. In our work, firstly, to increase the dispersity and stability of ND (size ~ 140 nm) in vitro under the physiological environment or in cell culture medium and be suitable for biomedicine applications, ND was covalently conjugated with biocompatible polymers, such as hydroxy-polyethylene glycol-4000 (PEG-4000). Secondly, doxorubicin hydrochloride (DOX), a chemotherapy drug, was physically adsorbed onto the PEGylated nanodiamond (ND-PEG-OH). These results revealed that ND-PEG-OH nanoparticle associated DOX (ND-PEG-DOX) could efficiently deliver the drug into the human liver cancer cells (HepG2) via a clathrin-dependent endocytosis pathway, and especially enhance the DOX uptake as compared to DOX alone. The uptake half-life of ND-PEG-DOX (t_1/2 = 3.31 h) was approximately two times that of free DOX uptake (t_1/2 = 1.67 h), which was related to the uptake pathway. The results from the confocal fluorescence microscopy study showed that DOX detached from ND-PEG-DOX composites inside the cytoplasm could migrate and enter the nucleolus to inhibit the cellular growth. Thirdly, in vitro dialysis determination and imaging experiments using the confocal fluorescence microscopy indicated that DOX released from ND-PEG-DOX composites had a slow and sustained drug release capability. In summary, our study has shown that ND-PEG-OH nanoparticles can act as effective drug carriers for cancer therapy.     

Fabrication of magnetic nanodot array using electrochemical deposition processes

We investigated fabrication processes of magnetic nanodot arrays for the ultra-high density magnetic recording media by using an electrodeposition. A CoZrNb underlayer was sputter-deposited on a glass disk substrate as a soft magnetic underlayer (SUL). Nano-patterns were formed on the substrate by UV-nanoimprint lithography (UV-NIL) and CoPt was electrodeposited into the nano-patterns. For obtaining uniform CoPt nanodot arrays with high perpendicular coercivities, we applied thin Cu intermediate layer on CoZrNb SUL and minimized its thickness. As a result, we obtained CoPt nanodot arrays with 150-nm diameter, 300-nm pitches, and 20-nm heights, which have uniform structures, on the substrates with the construction of Cu (1-2 nm)/CoZrNb (100 nm)/Cr (5 nm)/glass disk. The perpendicular coercivity of the CoPt nanodot arrays was as high as 5.4 kOe. From these results, we showed that the Cu intermediate layer with even 1-2 nm thick considerably improved the deposition condition on the substrates with CoZrNb SUL to successfully fabricate CoPt nanodot arrays with the diameter and pitches of 80 nm and 160 nm with sufficient uniformity.     

以多孔氧化铝为模板钴纳米线阵列的制备

以多孔氧化铝为模板,采用交流电沉积的方法制备了钴纳米线阵列膜.采用扫描电子显微镜(SEM)对电沉积钴纳米线前后的多孔氧化铝模板的形貌进行表征,通过透射电子显微镜(TElM)观察钴纳米线的表面形貌.结果表明:金属钴沉积到多孑L氧化铝模板的纳米孑L中,钴纳米线的平均直径约为50n/n,与氧化铝模板的孔径相一致.     

Piezo-actuated nanodiamond cantilever technology for high-speed applications

Diamond cantilever actuators show high resonance frequencies but need also high actuation forces, pointing towards piezoelectric actuation by a PZT/diamond unimorph. In this study lead zirconate titanate (Pb(Zr,Ti)O₃, PZT) layers have been deposited onto nanocrystalline diamond films by sol–gel deposition, to realize high-speed MEMS actuators. The fabrication technology is based on self-aligned patterning and on optical lithography. A mechanical resonance frequency of 3.9 MHz has been obtained for 30 µm cantilever length dominated by the nanodiamond Young's modulus of approximately 1000 GPa.     

Fabrication of highly ordered pore array in anodic aluminum oxide

Highly ordered pore array in anodic aluminum oxide was fabricated by anodizing pure aluminum. The order of a pore array was affected by anodizing voltage, electrolyte temperature, and first anodizing time. A regular pore array with mean diameter of 24 nm and interpore distance of 109 nm could be formed by two-step anodization at 40 V., oxalic acid concentration of 0.3 M and electrolyte temperature of 15 ‡C. The measured interpore distance showed linearity with anodizing voltage. The diameter of pores was adjusted by pore widening treatment in a 5 wt% phosphoric acid solution at 30 ‡C after two step anodization. The mechanism of self-arrangement of pores could be explained by the repulsive interaction between the pore walls.     

Fabrication of high-aspect-ratio micro piezoelectric array by powder injection molding

A powder injection molding process to fabricate a high-aspect-ratio piezoelectric microarray was developed. The reverse shaped sacrificial mold insert was developed by X-ray micromachining, and then insert-type injection molding was conducted to fabricate the piezoelectric microarray structure. For the micro-powder injection molding, rheological properties of the powder binder mixture were evaluated and analyzed. The measured flow behavior exponent was 0.44 and the flow activation energy was 83 kJ/mol⁻¹. Based on the analyzed rheological property, injection molding conditions were optimized. The rheological property and the injection molding conditions were crucial to ensure complete filling. Using the optimized conditions, two high-aspect-ratio piezoelectric microarrays were fabricated: (i) 20-μm patterns with 1:5 aspect ratio and (ii) 40-μm patterns with 1:10 aspect ratio.     

Fabrication and characterization of well-aligned and ultra-sharp silicon nanotip array

Well-defined, uniform, and large-area nanoscaled tips are of great interest for scanning probe microscopy and high-efficiency field emission. An ultra-sharp nanotip causes higher electrical field and, hence, improves the emission current. In this paper, a large-area and well-aligned ultra-sharp nanotip arrays by reactive ion etching and oxidation techniques are fabricated. The apex of nanotips can be further sharpened to reach 3-nm radius by subsequent oxidation and etching process. A schematic model to explain the formation of nanotip array is proposed. When increasing the etching time, the photoresist on top of the nanotip is also consumed, and the exposed silicon substrate is etched away to form the nanotip. At the end, the photoresist is consumed completely and a nanotip with pyramid-like shape is developed. The field emission property was measured, and the turn-on field and work function of the ultra-sharp nanotip was about 5.37 V/μm and 4.59 eV, respectively. A nanotip with an oxide layer capped on the sidewall is also fabricated in this paper. Comparing to the uncapped nanotip, the oxide-capped sample exhibits stable and excellent field emission property against environmental disturbance.     

Fabrication of wafer-level double-sided microlens array using injection compression molding

Double-sided microlens arrays (MLAs) are the key optical components of the optical component. To enhance microlens fabrication productivity, a wafer-level, double-sided MLA was designed and fabricated using injection compression molding (ICM). First, the Moldex3D simulation analysis results show that the design of the disc mold saves material and representation time than the multi-cavity mold. The 4-inch disc mold with a 4 × 4 double-sided MLA of two inserts was used to do the study. The L9 orthogonal Taguchi method was employed to find the best combination of molding parameters. For molding experiments, 2 mold inserts with 4 × 4 convex and concave lens arrays were machined by the ultraprecision diamond turning. They were mounted into molds in one of two locations, either close to the gate or far from the gate. The molding experiment results confirmed that the ICM-molded MLA was better than the injection molding (IM)-molded one, with higher precision and lower residual stress. The results were similar to the simulations. The ICM molded MLA has a focal length of 2.549 mm and a spot size of 50 μm and the total deviation percentage is less than 1%. This study proves the feasibility of fabricating a wafer-level, double-sided MLA disc using ICM.     

Hyperbranched polyglycerol modified fluorescent nanodiamond for biomedical research

The aim of the present work was to functionalize fluorescent nanodiamond by covalent grafting with hyperbranched polyglycerol. Fluorescent nanodiamond, derived from high pressure high temperature micron-sized diamond, was oxidized and then thermally reacted with pure glycidol in the absence of catalyst. The results revealed that thermal polymerization of glycidol was notably faster on the nanodiamond surface as a result of a surface initiation of the isothermal ring opening polymerization. Interestingly, the aqueous dispersion of the resulting nanoparticles appeared stable at high ionic strength. Furthermore, the fluorescent nanodiamond grafted with hyperbranched polyglycerol displayed several hydroxyl end-groups which could be further derivatized by carboxylation or carbamatization and subsequently conjugated with protein linked via an amide bound. Notably, nanodiamonds retain their unique fluorescent characteristics. This work suggests that fluorescent nanodiamond coated with hyperbranched glycidol could be promising in biomedical research where aqueous dispersion of fluorescent nanoparticles stable in physiological medium is in high demand to label, track and quantify biomolecules.     

PEGylation and polyPEGylation of nanodiamond

Polyethylene glycol (PEG) and poly(PEGMA) conjugated nanodiamond (ND) have been synthesized via “grafting to” and “grafting from” methods, respectively. In “grafting to” method, hydroxyl groups on ND surface were firstly oxidized to carboxyl groups, and then reacted with thionyl chloride to form acyl chloride groups. The acyl chloride functionalized ND (ND–COCl) was subsequently reacted with poly(ethylene glycol) monomethyl ether (mPEG) in the presence of triethylamine to generate mPEG conjugated ND (ND–mPEG). On the other hand, in “grafting from” method, ND–OH was modified with 2-bromoisobutyryl bromide (ND–Br), and then poly(PEG methyl ether methacrylate) (Poly(PEGMA)) chains were linked on the ND surface through surface-initiated atom transfer radical polymerization (ATRP) using ND–Br as the initiator and Cu(Br)/N,N,N′,N″,N″-pentmethyl diethylenetriamine (PMDETA) as the catalyst and ligand. The polymer conjugated ND particles were characterized using transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). TGA analyses demonstrated that the polymer weight ratios through “grafting to” and “grafting from” methods were 29.8% and 34.4%, respectively. The mPEG and poly(PEGMA) conjugated ND nanoparticles exhibited enhanced dispersibility in organic media. More importantly, due to the relative high graft ratios and molecular weight, poly(PEGMA) functionalized ND was also dispersed well in water. Given the excellent physicochemical and biological properties of PEG and ND, the methods described in current work might be useful for the preparation of functional ND nanoparticles for potential biomedical applications.     

脉冲电沉积制备InSb/Sb超晶格纳米线阵列

采用脉冲电沉积技术在氧化铝模板中制备得到直径60 nm的InSb/Sb超晶格纳米线阵列,并运用扫描电镜、透射电镜和电子能谱仪对其形貌与结构进行了表征与测试。高度有序的InSb/Sb超晶格纳米线长度约为40 μm,其长径比超过600。实验中,通过改变沉积电压与时间达到了对超晶格纳米线组分与结构的控制, 纳米线阵列中In与Sb的原子质量比接近于1/2,在每个周期中,InSb的厚度为12 nm,Sb相似文献   

Plasma pressure compaction of nanodiamond

Detonation synthesized nanodiamond (ND) was sintered using a Plasma Pressure Compaction (P²C) technique. Sintering was performed for 1 min at temperatures between 700 and 1200 °C, and for 1–10 min at 900 °C under 65 MPa pressure. Structure and composition of the sintered samples were analyzed by X-ray diffraction, transmission electron microscopy and Raman microspectroscopy. The selected sintering conditions prevent excessive graphitization of diamond and allow formation of porous pellets having the density of 1.3–1.6 g/cm³, hardness > 0.1 GPa and Young's modulus > 3 GPa. The sintered ND pellets with porosity of about 50% have mechanical properties sufficient for handling and can be infiltrated to produce ND composites.     

Epoxidation of 1-hexene with hydrogen peroxide over nitrogen-incorporated TS-1 zeolite

Nitrogen-incorporated TS-1 zeolite (N-TS-1) was synthesized by direct calcining the as-synthesized TS-1 powder in NH₃ flow at high temperature. Epoxidation of 1-hexene with dilute H₂O₂ over N-TS-1 was studied. The results showed that the catalytic activity and selectivity of TS-1 were greatly improved upon post-synthetic nitridation. A new TiOOH intermediate with double hydrogen bonds was proposed. The new intermediate was more stable due to the presence of another hydrogen bond, which was formed between the stable nitrogen species and the H atom of the conventional five-member-ring intermediate, thereby improving the epoxidation activity.     

Fabrication of size-controllable Fe2O3 nanoring array via colloidal lithography

Tailed-Fe(2)O(3) ring arrays are fabricated by solution-dipping on a colloidal monolayer template. The influence of synthesis parameters on the quality of nanostructures has been investigated. The ring size can be controlled by changing the precursor concentration and varying the annealing time of the polystyrene sphere colloidal monolayer. In addition, the edge of the rings is sensitive to the surface tension of precursor solution, and high quality ordered ring arrays can be obtained by tuning the surface tension. This strategy allows the fabrication of specific metal oxides ring arrays with high quality and uniform morphology.