High Density 3D Carbon Tube Nanoarray Electrode Boosting the Capacitance of Filter Capacitor

Electric double-layer capacitors(EDLCs)with fast frequency response are regarded as small-scale alternatives to the commercial bulky aluminum electrolytic capacitors.Creating carbon-based nanoarray electrodes with precise alignment and smooth ion channels is crucial for enhancing EDLCs’performance.However,controlling the density of macropore-dominated nanoarray electrodes poses challenges in boosting the capacitance of line-filtering EDLCs.Herein,a simple technique to finely adjust the vertical-pore diameter and inter-spacing in three-dimensional nanoporous anodic aluminum oxide(3D-AAO)template is achieved,and 3D compactly arranged carbon tube(3D-CACT)nanoarrays are created as electrodes for symmetrical EDLCs using nanoporous 3D-AAO template-assisted chemical vapor deposition of carbon.The 3D-CACT electrodes demonstrate a high surface area of 253.0 m^(2) g^(−1),a D/G band intensity ratio of 0.94,and a C/O atomic ratio of 8.As a result,the high-density 3D-CT nanoarray-based sandwich-type EDLCs demonstrate a record high specific areal capacitance of 3.23 mF cm^(-2) at 120 Hz and exceptional fast frequency response due to the vertically aligned and highly ordered nanoarray of closely packed CT units.The 3D-CT nanoarray electrode-based EDLCs could serve as line filters in integrated circuits,aiding power system miniaturization.

3D Grid of Carbon Tubes with Mn3O4-NPs/CNTs Filled in their Inner Cavity as Ultrahigh-Rate and Stable Lithium Anode

Transition metal oxides are regarded as promising candidates of anode for next-generation lithium-ion batteries(LIBs)due to their ultrahigh theoretical capacity and low cost,but are restricted by their low conductivity and large volume expansion during Li^(+)intercalation.Herein,we designed and constructed a structurally integrated 3D carbon tube(3D-CT)grid film with Mn_(3)O_(4)nanoparticles(Mn_(3)O_(4)-NPs)and carbon nanotubes(CNTs)filled in the inner cavity of CTs(denoted as Mn_(3)O_(4)-NPs/CNTs@3D-CT)as high-performance free-standing anode for LIBs.The Mn_(3)O_(4)-NPs/CNTs@3D-CT grid with Mn_(3)O_(4)-NPs filled in the inner cavity of 3D-CT not only afford sufficient space to overcome the damage caused by the volume expansion of Mn_(3)O_(4)-NPs during charge and discharge processes,but also achieves highly efficient channels for the fast transport of both electrons and Li+during cycling,thus offering outstanding electrochemical performance(865 mAh g^(-1)at 1 A g^(-1)after 300 cycles)and excellent rate capability(418 mAh g^(-1)at 4 A g^(-1))based on the total mass of electrode.The unique 3D-CT framework structure would open up a new route to the highly stable,high-capacity,and excellent cycle and high-rate performance free-standing electrodes for highperformance Li-ion storage.

Ultrahigh-power electrochemical double-layer capacitors based on structurally integrated 3D carbon tube arrays

The rational design of electrodes is the key to achieving ultrahigh-power performance in electrochemical energy storage devices.Recently,we have constructed well-organized and integrated three-dimensional(3D)carbon tube(CT)grids(3D-CTGs)using a 3D porous anodic aluminum oxide template-assisted method as electrodes of electrical double-layer capacitors(EDLCs),showing excellent frequency response performance.The unique design warrants fast ion migration channels,excellent electronic conductivity,and good structural stability.This study achieved one of the highest carbon-based ultrahigh-power EDLCs with the 3D-CTG electrodes,resulting in ultrahigh power of 437 and 1708 W·cm−3 with aqueous and organic electrolytes,respectively.Capacitors constructed with these electrodes would have important application prospects in the ultrahigh-power output.The rational design and fabrication of the 3D-CTGs electrodes have demonstrated their capability to build capacitors with ultrahighpower performance and open up new possibilities for applications requiring high-power output.

Hexagonally arranged arrays of urchin-like Ag hemispheres decorated with Ag nanoparticles for surface-enhanced Raman scattering substrates

The surface topography of noble metal particles is a significant factor in tailoring surface-enhanced Raman scattering （SERS） properties. Here, we present a simple fabrication route to hexagonally arranged arrays of surface-roughened urchin- like Ag hemispheres （Ag-HSs） decorated with Ag nanoparticles （Ag-NPs） for highly active and reproducible SERS substrates. The urchin-like Ag-HS arrays are achieved by sputtering Ag onto the top surface of a highly ordered porous anodic aluminum oxide （AAO） template to form ordered arrays of smooth Ag-HSs and then by electrodepositing Ag-NPs onto the surface of each Ag-HS. Owing to the ordered arrangement of the Ag-HSs and the improved surface roughness, the urchin-like hierarchical Ag-HS arrays can provide sufficient and uniform ＂hot spots＂ for reproducible and highly active SERS effects. Using the urchin-like Ag-HS arrays as SERS substrates, 10-7 M dibutyl phthalate （a member of plasticizers family） and 1.5 × 10-5 M PCB-77 （one congener of polychlorinated biphenyl, a notorious class of pollutants） are identified, showing promising potential for these substrates in the rapid recognition of organic pollutants.

Plasmon-tunable Au@Ag core-shell spiky nanoparticles for surfaceenhanced Raman scattering

A facile synthetic approach has been developed to prepare uniform and size-tunable spiky Au@Ag core-shell nan oparticles (NPs) to tailor the localized surface plasm on res onance (LSPR) properties. The gradual assembly of small Au nano crystals allows the size of spiky Au NPs to be modulated from tens to several hundreds of nano meters by tuning the concentration of initial Au seeds and Au source;and the thick ness of the Ag shell can be adjusted with stepwise reduction of Ag(l)ions. The LSPR bands of such spiky Au@Ag core-shell NPs resemble those of pure spiky Au NP cores of similar sizes in near-infrared region, and increasing the Ag shell thickness results in a blue shift and broadening of the LSPR band in the n ear-i nfrared regi on. Additi on ally, the spiky Au@Ag core-shell NPs exhibit improved surface-e nhan ced Rama n scattering (SERS) activity as compared to the bare spiky Au NPs and spherical Ag@Au NPs. This work has offered a facile route to synthesize plasmonic metal NPs with LSPR band in 650 to 800 nm that show strong enhancement of localized electromagnetic field, which provides an effective SERS substrate for SERS imaging and detection in biological fluids and tissues.

Polyacrylic acid sodium salt film entrapped Ag-nanocubes as molecule traps for SERS detection

Surface-enhanced Raman spectroscopy （SERS） is a fast analytical technique for trace chemicals; however, it requires the active SERS-substrates to adsorb analytes, thus limiting target species to those with the desired affinity for substrates. Here we present networked polyacrylic acid sodium salt （PAAS） film entrapped Ag-nanocubes （denoted as Ag-nanocubes@PAAS） as an effective SERS-substrate for analytes with and without high affinity. Once the analyte aqueous solution is cast on the dry Ag-nanocubes@PAAS substrate, the bibulous PAAS becomes swollen forcing the Ag-nanocubes loose, while the analytes diffuse in the interstices among the Ag-nanocubes. When dried, the PAAS shrinks and pulls the Ag-nanocubes back to their previous aggregated state, while the PAAS network ＂detains＂ the analytes in the small gaps between the Ag-nanocubes for SERS detection. The strategy has been proven effective for not only single- analytes but also multi-analytes without strong affinity for Ag, showing its potential in SERS-based simultaneous multi-analyte detection of both adsorbable and non-adsorbable pollutants in the environment.

ZnO-nanotaper array sacrificial templated synthesis of noble-metal building-block assembled nanotube arrays as 3D SERS-substrates

This paper describes a ZnO-nanotaper array sacrificial templated synthetic approach for the fabrication of the arrays of nanotubes with tube-walls assembled by building-blocks of Ag-nanoplates, Au-nanorods, Pt-nanothorns or Pd-nanopyramids, thus possessing high-density 3D ＂hot spots＂ in sub-10-nm gaps of neighboring building blocks with nano-tips, -corners or -edges. Additionally, these hierarchical nanostructure arrays possess high surface area with rich surface chemistry, being beneficial to capturing the analyte. The Ag-nanoplate- assembled nanotube arrays can be used as sensitive surface-enhanced Raman scattering （SERS） substrates with good signal uniformity and reproducibility. Using such Ag hierarchical nanostructure arrays as SERS-substrates, not only has 10-14 M rhodamine 6G been identified, but also 10-7 M polychlorinated biphenyls （PCBs, a notorious class of persistent organic pollutants） are recognized, and even two congeners of PCBs can be identified in a mixture, showing the potential applications of the materials in SERS-based rapid detection of environmental organic pollutants.

Synthesis of Vertically Oriented GaN Nanowires on a LiAlO_(2) Substrate via Chemical Vapor Deposition

Vertically oriented nanowires(NWs)of single-crystalline wurtzite GaN have been fabricated on a-LiAlO_(2)(100)substrate coated with a Au layer,via a chemical vapor deposition process at 1000℃ using gallium and ammonia as source materials.The GaN NWs grow along the nonpolar[10]direction with steeply tapering tips,and have triangular cross-sections with widths of 50100 nm and lengths of up to several microns.The GaN NWs are formed by a vapor liquid solid growth mechanism and the tapering tips are attributed to the temperature decrease in the final stage of the synthesis process.The aligned GaN NWs show blue-yellow emission originating from defect levels,residual impurities or surface states of the GaN NWs,and have potential applications in nanotechnology.