In Situ Raman Monitoring of Trace Antibiotics in Different Harsh Water Environments

In situ surface-enhanced Raman scattering(SERS)is a widely used operando analytical technique,while facing numerous complex factors in applications under aqueous environment,such as low detection sensitivity,poor anti-interference capability,etc.,resulting in unreliable detectability.To address these issues,herein a new hydrophobic SERS strategy has been attempted.By comprehensively designing and researching a SERS-active structure of superhydrophobic ZnO/Ag nanowires,we demonstrate that hydrophobicity can not only draw analytes from water onto substrate,but also adjust"hottest spot"from the bottom of the nanowires to the top.As a result,the structure can simultaneously concentrate the dispersed molecules in water and the enhanced electric field in structure into a same zone,while perfecting its own anti-interference ability.The underwater in situ analytical enhancement factor of this platform is as high as 1.67×10^(11),and the operando limited of detection for metronidazole(MNZ)reaches to 10^(-9)M.Most importantly,we also successfully generalized this structure to various real in situ detection scenarios,including on-site detection of MNZ in corrosive urine,real-time warning of wrong dose of MNZ during intravenous therapy,in situ monitoring of MNZ in flowing wastewater with particulate interference,etc.,demonstrating the great application potential of this hydrophobic platform.This work realizes a synergistic promotion for in situ SERS performance under aqueous environment,and also provides a novel view for improving other in situ analytical techniques.

Tuning the Water Desalination Performance of Graphenic Layered Nanomaterials by Element Doping and Inter-Layer Spacing

Through atomic molecular dynamics simulations,we investigate the performance of two graphenic materials,boron(BC3)and nitrogen doped graphene(C3 N),for seawater desalination and salt rejection,and take pristine graphene as a control.Effects of inter-layer separation have been explored.When water is filtered along the transverse directions of three-layered nanomaterials,the optimal inter-layer separation is 0.7–0.9 nm,which results in high water permeability and salt obstruction capability.The water permeability is considerably higher than porous graphene filter,and is about two orders of magnitude higher than commercial reverse osmosis(RO)membrane.By changing the inter-layer spacing,the water permeability of three graphenic layered nanomaterials follows an order of C3 N≥GRA>BC3 under the same working conditions.Amongst three nanomaterials,BC3 is more sensitive to inter-layer separation which offers a possibility to control the water desalination speed by mechanically changing the membrane thickness.This is caused by the intrinsic charge transfer inside BC3 that results in periodic distributed water clusters around the layer surface.Our present results reveal the high potentiality of multi-layered graphenic materials for controlled water desalination.It is hopeful that the present work can guide design and fabrication of highly efficient and tunable desalination architectures.

Ferroelectrically modulate the Fermi level of graphene oxide to enhance SERS response

Surface-enhanced Raman scattering(SERS)substrates based on chemical mechanism(CM)have received widespread attentions for the stable and repeatable signal output due to their excellent chemical stability,uniform molecular adsorption and controllable molecular orientation.However,it remains huge challenges to achieve the optimal SERS signal for diverse molecules with different band structures on the same substrate.Herein,we demonstrate a graphene oxide(GO)energy band regulation strategy through ferroelectric polarization to facilitate the charge transfer process for improving SERS activity.The Fermi level(Ef)of GO can be flexibly manipulated by adjusting the ferroelectric polarization direction or the temperature of the ferroelectric substrate.Experimentally,kelvin probe force microscopy(KPFM)is employed to quantitatively analyze the Ef of GO.Theoretically,the density functional theory calculations are also performed to verify the proposed modulation mechanism.Consequently,the SERS response of probe molecules with different band structures(R6G,CV,MB,PNTP)can be improved through polarization direction or temperature changes without the necessity to redesign the SERS substrate.This work provides a novel insight into the SERS substrate design based on CM and is expected to be applied to other two-dimensional materials.

Modulated optical and ferroelectric properties in a lateral structured ferroelectric/semiconductor van der Waals heterojunction

Modulation between optical and ferroelectric properties was realized in a lateral structured ferroelectric CuInP_(2)S_(6)(CIPS)/semiconductor MoS_(2) van der Waals heterojunction.The ferroelectric hysteresis loop area was modulated by the optical field.Two types of photodetection properties can be realized in a device by changing the ON and OFF states of the ferroelectric layer.The device was used as a photodetector in the OFF state but not in the ON state.The higher tunnelling electroresistance(~1.4×10^(4))in a lateral structured ferroelectric tunnelling junction was crucial,and it was analyzed and modulated by the barrier height and width of the ferroelectric CIPS/semiconductor MoS_(2) Schottky junction.The new parameter of the ferroelectric hysteresis loop area as a function of light intensity was introduced to analyze the relationship between the ferroelectric and photodetection properties.The proposed device has potential application as an optoelectronic sensory cell in the biological nervous system or as a new type of photodetector.

Study of thermoelectric enhanced SERS and photocatalysis with ZnO-metal nanorod arrays

Herein,a thermoelectric induced surface-enhanced Raman scattering(SERS)substrate consisting of ZnO nanorod arrays and metal nanoparticles is proposed.The intensities of SERS signals are further enhanced by an order of magnitude and the limit of detection(LOD)for the molecules is reduced by at least one order of magnitude after the application of a thermoelectric potential.The enhancement mechanism is analyzed carefully and thoroughly based on the experimental and theoretical results,thus proving that the thermoelectric-induced enhancement of the SERS signals should be classified as a chemical contribution.Furthermore,it is proved that the electric regulation mechanism is universally applicable,and the fabricated substrate realizes enormous enhancements for various types of molecules,such as rhodamine 6G,methyl orange,crystal violet,amaranth,and biological molecules.Additionally,the proposed electric-induced SERS(E-SERS)substrate is also realized to monitor and manipulate the plasmon-activated redox reactions.We believe that this study can promote the course of the research on ESERS and plasmon-enhanced photocatalysts.

Passively mode-locked Er-doped fiber laser based on SnS2 nanosheets as a saturable absorber

In this paper, tin disulfide （SnS2）, a two-dimensional （2D） n-type direct bandgap layered metal dichalcogenide with a gap value of 2.24 eV, was employed as a saturable absorber. Its appearance and nonlinear saturable ab- sorption characteristics were also investigated experimentally. SnSz-PVA （polyvinyl alcohol） film was successfully prepared and employed as a mode-locker for achieving a mode-locked Er-doped fiber laser with a pulse width of 623 fs at a pulse repetition rate of 29.33 MHz. The results prove that SnS2 nanosheets will have wide potential ultrafast photonic applications due to their suitable bandgap value and excellent nonlinear saturable absorption characteristics.

Compact Q-switched 2 μm Tm:GdVO4 laser with MoS2 absorber

A molybdenum disulfide（Mo S2） saturable absorber was fabricated by thermally decomposing the ammonium thiomolybdate. By using the MoS2 absorber, a compact diode-pumped passively Q-switched Tm:GdVO4 laser has been demonstrated. A stable Q-switched laser with repetition rates from 25.58 to 48.09 kHz was achieved.Maximum average output power was 100 mW with the shortest pulse duration of 0.8 μs. Maximum pulse energy is 2.08 μJat center of 1902 nm.