Yongqiang Wen

Dual-scaled porous nitrocellulose membranes with underwater superoleophobicity for highly efficient oil/water separation.

Large-area dual-scaled porous nitrocellulose (p-NC) membranes are fabricated by a facile, inexpensive and scalable perforating approach. These p-NC membranes show stable superhydrophilicity in air and underwater superoleophobicity. The p-NC membranes with intrinsic nanopores and array of microscale perforated pores could selectively and efficiently separate water from various oil/water mixtures with high efficiency (>99%) rapidly.

Controlled Inkjetting of a Conductive Pattern of Silver Nanoparticles Based on the Coffee‐Ring Effect

Conductive patterns with line widths of 5-10 µm are successfully fabricated by utilizing the coffee-ring effect in inkjet printing, resulting in transmittance values of up to 91.2% in the visible to near-infrared region. This non-lithographic approach broadens the range of fabrication procedures that can be used to create various nanoparticle-based microstructures and electronic devices.

Synthesis of monodisperse silver nanoparticles for ink-jet printed flexible electronics.

In this study, monodisperse silver nanoparticles were synthesized with a new reduction system consisting of adipoyl hydrazide and dextrose at ambient temperature. By this facile and rapid approach, high concentration monodisperse silver nanoparticles were obtained on a large scale at low protectant/AgNO(3) mass ratio which was highly beneficial to low cost and high conductivity. Based on the synthesized monodisperse silver nanoparticles, conductive inks were prepared with water, ethanol and ethylene glycol as solvents, and were expected to be more environmentally friendly. A series of electrocircuits were fabricated by ink-jet printing silver nanoparticle ink on paper substrate with a commercial printer, and they had low resistivity in the range of 9.18 × 10( - 8)-8.76 × 10( - 8) Ω m after thermal treatment at 160u2009°C for 30 min, which was about five times that of bulk silver (1.586 × 10( - 8) Ω m). Moreover, a radio frequency identification (RFID) antenna was fabricated by ink-jet printing, and 6 m wireless identification was realized after an Alien higgs-3 chip was mounted on the printed antenna by the flip-chip method. These flexible electrocircuits produced by ink-jet printing would have enormous potential for low cost electrodes and sensor devices.

Programmable DNA switch for bioresponsive controlled release

A bioresponsive controlled release system based on mesoporous silica nanoparticles (MS) was designed and constructed. Through the DNAa/DANb assembly, DNAb-modified gold nanoparticles (AuNPs-DNAb) could be attached to the pores of MS covalently functionalized with DNAa. In the presence of adenosine, the pores of MS could be opened and the encapsulated guest was released, due to the interaction between DNAb and adenosine. Forster resonance energy transfer (FRET) was used to confirm the switching mechanism. Furthermore, the carry system was exclusively responsive to adenosine, and the process was dependent on the concentration of adenosine, which made the system promising for target-directing controlled release.

Fabrication of closed-cell polyimide inverse opal photonic crystals with excellent mechanical properties and thermal stability

Closed-cell polyimide IOPCs were fabricated using core–shell poly(styrene–methyl methacrylate–acrylic acid) colloidal spheres as a template. For comparison, open-cell polyimide IOPCs were also prepared using polystyrene colloidal spheres as a template. The polyimide IOPCs with a closed-cell structure had much better mechanical properties than those with open-cell structures. Moreover, the photonic band gap and superhydrophobicity of the closed-cell polyimide IOPCs could be maintained even after they were treated at 400 °C for 2 h. These closed-cell polyimide IOPCs were the stablest polymer photonic crystals under high temperature conditions, and would have great potential applications in thermal insulation, energy absorption and aerospace.

A non-planar organic molecule with non-volatile electrical bistability for nano-scale data storage

A new non-planar organic molecule with electron donor and acceptor capabilities was synthesized for nano-scale data storage. Macroscopic I–V characteristics of organic crystalline thin films indicate that the non-planar molecule possesses good electrical bistability. Nano-scale recording dots with an average diameter of 2.5 nm were realized by scanning tunneling microscopy.

Ultrahigh density data storage based on organic materials with SPM techniques

With the ever-increasing demand of expansive storage capacity and the continuous miniaturization of optoelectronic device, ultrahigh density data storage has attracted intensive research interest. In this feature article, recent progress on the developments of ultrahigh density data storage based on organic materials is summarized and discussed, it especially focuses on materials for data recording using scanning tunneling microscopy (STM), atom force microscopy (AFM), and scanning near-field microscopy (SNOM). The focus is placed on the rational design and synthesis of new organic recording media to realize and improve nanoscale data storage. In addition, an outlook in this field is also discussed.

High-performance optoelectrical dual-mode memory based on spiropyran-containing polyimide

A thermally stable polyimide (PI-SP) was designed as a functional material for the fabrication of memory device, and its optoelectrical dual-mode memory was studied. In an Al/PI-SP/Al device, the memory can be switched on with the negative or positive voltage with the on/off current ratios of about 104. Besides, the PI-SP can also undergo the reversibly photochromic reactions in solution or solid state with high fatigue resistance, which can serve as optical recording material. The PI-SP based device can exhibit the electrical and optical switching properties independently, while their cooperative switching properties cannot be realized simultaneously.

Novel Thermally Stable Single-Component Organic-Memory Cell Based on Oxotitanium Phthalocyanine Material

This letter reports a novel single-component organic-memory cell based on oxotitanium phthalocyanine (TiOPc) material. The device can achieve good resistive-switching performance such as a high on/off current ratio of about 104, large read signal window (4 V), and good retention (4 h at 1-V read voltage). The organic-memory cell exhibits excellent thermal stability above 525 K due to the thermal robustness of TiOPc, which indicates its potential for hybrid integration with CMOS technology at the back-end process and flexible electronics system. The current-voltage characteristics are comprehensively investigated, and a possible mechanism is proposed and well fitted with the experimental data. The results show that the trap-filling space-charge-limited conduction with TiOPc charge confinement and the electrochemical reaction at the Al/TiOPc interface can elucidate the switching behavior of the memory cell.

Enhanced nanoparticle-oligonucleotide conjugates for DNA nanomachine controlled surface-enhanced Raman scattering switch

In this letter, a pH-responsive surface-enhanced Raman scattering (SERS) switching system based on the controlled organization of silver nanoparticles (AgNPs) by DNA nanomachine has been designed. In this system, the polyvalent linkages between AgNPs and cyclic disulfide groups-modified DNA tremendously increased the stability of the AgNP-DNA conjugates. Using this kind of conjugates, the SERS enhancement was demonstrated with good controllability and reproducibility through the controlled formation/deformation of SERS “hotspots” by the adjustment of pH of aqueous media.