Film wrap nanoparticle system with the graphene nano-spacer for SERS detection.

Film wrap nanoparticle system (FWPS) is proposed and fabricated to perform SERS effect, where the Ag nanoparticle was completely wrapped by Au film and the double-layered graphene was selected as the sub-nano spacer. In this system, the designed nanostructure can be fully rather than partly used to generate hotspots and absorb probe molecules, compared to the nanoparticle to nanoparticle system (PTPS) or nanoparticle to film system (PTFS). The optimal fabricating condition and performance of this system were studied by the COMSOL Multiphysics. The simulation results show that the strongly large-scale localized electromagnetic field appears in the whole space between the Ag nanoparticle and Au film. The experimental results show that the FWPS presents excellent sensitivity (crystal violet (CV): 10-11 M), uniformity, stability and high enhancement factor (EF: 2.23×108). Malachite green (MG; 10-10 M) on the surface of fish and DNA strands with different base sequence (A, T, C) were successfully detected. These advanced results indicate that FWPS is highly promising to be applied for the detection of environmental pollution and biomolecules.

Effect of polyethylene terephthalate plastics on nitrogen, sulphur and chlorine contaminants via sludge pyrolysis and Pb/Cu adsorption properties of biochar.

Pyrolysis is an effective process for disposing of municipal sewage sludge (SS). Plastics can affect the SS pyrolysis behaviour and pyrolysis products due to their low ash and high hydrocarbon ratio. The secondary pollutants from the pyrolysis process may also be affected. Therefore, polyethylene terephthalate (PET), a typical plastic, was chosen to investigate the release characteristics of pollutants containing nitrogen, sulphur, and chlorine via SS pyrolysis, and the changes of biochar to adsorb two typical heavy metals, Pb and Cu. The pyrolysis of PET plastics facilitates the migration of N toward solid and liquid-phase products, S and Cl to the gas-phase products via pyrolysis. Oxygenated compounds of pyrolytic volatiles decreased from 38.18% to 28.43%, concurrently promoting the formation of phenolic compounds. The co-pyrolysis improved the quality of biochar and the ability to adsorb Pb and Cu. This systematic study can provide some support for the further improvement of SS pyrolysis technology, and will also be beneficial for subsequent applications.

Building a flexible and applicable sodium ion full battery based on self-supporting large-scale CNT films intertwined with ultra-long cycling NiCo2S4.

The major difficulties for the development of flexible energy storage batteries lie in the scalable manufacture of high-performance flexible electrodes with bending tolerance. In the present study, large-scale CNT films are prepared by a continuous production method and used to fabricate a self-supported flexible high-capacity conversion anode with ultra-long cycling life by the in situ growth of NiCo2S4 nanosheets tightly anchored on the CNTs. The CNTs produced via such a scalable method have interconnected porous channels, providing a large contact area between the active materials and electrolyte facilitating the electrochemical conversion reaction of NiCo2S4. An ultra-high rate capability is achieved in terms of a capacity of 280 mA h g-1 at 20 A g-1. The interlaced construction of NiCo2S4 nanosheets with CNTs and firm anchoring on the CNT film result in a remarkable ultra-long cyclability of the NiCo2S4/CNT electrode with a capacity retention rate of 96% after 7500 cycles. A flexible full battery device is further established with the NiCo2S4/CNT anode and Na3V2(PO4)3/CNT cathode with the sealed package of PDMS, exhibiting good cycling stability and mechanical durability under different bending states. The present work highlights a scalable flexible battery electrode material, and demonstrates its potential applications in flexible Na-ion batteries.

Three-dimensional SERS sensor based on the sandwiched G@AgNPs@G/PDMS film.

Three-dimensional (3D) SERS substrate with the denser "hotspots" is synthesized by the constriction of PDMS film decorated with sandwiched graphene@AgNPs@graphene (G@AgNPs@G) nanostructure. Graphene layers above and below the AgNPs are used to absorb molecules onto the "hotspots", and prevent the oxidation of AgNPs in our design. PDMS films can be easily shrunk for 3D structures, causing advantages in enhancement ability and light-matter interaction. Benefiting from the above advantages, a detection limit of 10-14 M (CV) and enhancement factor (EF) of 3.9 × 109 were obtained in our experiment. Theoretical analyses (FDTD) were also used to study the enhancement mechanism. For practical purposes, in-situ detection of MG molecules on the fish surface and the label-free detection of DNA base of adenine (A) and cytosine (C) were also studied. The high enhancement factor, great sensitivity, reliability, and stability of substrate reasonably proved that it can be used as an excellent SERS substrate for biomolecular detection.

Plasma treated graphene FET sensor for the DNA hybridization detection.

Room-temperature plasma treated graphene based FET was firstly proposed for the DNA hybridization detection. Affinity and electrical properties of the graphene based DNA-FET sensor were studied and improved benefits from the surface modification. The facile room-temperature Ar plasma easily removes residues from the graphene surface and changes the hydrophilic properties of graphene, which is important for our solution gated DNA-FET sensor. Limit of the detection of below 10 aM is obtained in our experiment. Especially, DNA concentration (CDNA)/the amount of net drain current (ΔI) and the negative shift in the VCNP value of the GFET sensor with the plasma treated 30 s are all improved compared with that without treatment. It shows that the easily plasma treatment of the graphene surface can be used for the solution gated FET sensor.

Donor effect dominated molybdenum disulfide/graphene nanostructure-based field-effect transistor for ultrasensitive DNA detection.

Field effect transistor (FET) biosensors based on low-dimensional materials have the advantages of small in size, simple structure, fast response and high sensitivity. In this work, a field-effect transistor biosensor based on molybdenum disulfide/graphene (MoS2/graphene) hybrid nanostructure was proposed and fabricated for DNA hybridization detection. The biosensor achieved an effective response to DNA concentrations in a broad range from 10 aM to 100 pM and a limit of detection (LOD) of 10 aM was obtained, which was one or more orders of magnitude lower than the reported result. The sensing mechanisms (donor and gating effects) of the FET sensor were discussed. A larger voltage shift of the charge neutral point was obtained due to a strengthened donor effect and a weakened gating effect caused by the introduction of MoS2 layers. Such FET sensor shows high specificity for different matching degrees of complementary DNA, indicating the potential use of such a sensor in disease diagnosis.