Photophysical properties of nitrogen-doped carbon quantum dots synthesized by graphite

Here,nitrogen-doped carbon quantum dots(N-CQDs)were successfully synthesized by the solvothermal method using graphite as the carbon source and N,N-dimethylformamide as the nitrogen source.We characterized the structure and chemical constitution of N-CQDs using X-ray diffraction,Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.We investigated the pump-and temperature-dependent photoluminescence(PL)properties and the dynamic exciton recombination processes of N-CQDs,using both steady-state and time-resolved PL techniques.The spectral results show that the PL emission peak located at 518 nm at room temperature,mainly originates from the n-π∗transition on the surface of N-CQDs.The pump fluence and PL integral intensity were analyzed to demonstrate the existence of single-photon excitation under the 405 nm laser excitation.As the temperature increases,the non-radiative transition gradually increases,which decreases the PL intensity,the full width at half maxima first narrows and then widens and the PL lifetime gradually decreases.Furthermore,we combined the N-CQDs with chip to prepare light-emitting diode(LED).The resulting chromaticity coordinate was obtained to be(0.29,0.40).This study offers a comprehensive understanding of the luminescence mechanism in N-doped CQDs and introduces a novel approach for the quickly fabrication of full-color display LEDs.

Synchronous regulation of morphology and electronic structure of FeNi-P nanosheet arrays by Zn implantation for robust overall water splitting

FeNi-based phosphides are one of the most hopeful electrocatalysts,whereas the significant challenge is to achieve prominent bifunctional catalytic activity with low voltage for water splitting.The morphology and electronic structure of FeNi-based phosphides can intensively dominate effective catalysis,therefore their simultaneous regulating is extremely meaningful.Herein,a robust bifunctional catalyst of Zn-implanted FeNi-P nanosheet arrays(Zn-FeNi-P)vertically well-aligned on Ni foam is successfully fabricated by Zn implanting strategy.The Zn fulfills the role of electronic donor due to its low electronegativity to enhance the electronic density of FeNi-P for optimized water dissociation kinetics.Meanwhile,the implantation of Zn into FeNi-P can effectively regulate morphology of the catalyst from thick and irregular nanosheets to ultrathin lamellar structure,which generates enriched catalytic active sites,leading to accelerating electron/mass transport ability.Accordingly,the designed Zn-FeNi-P catalyst manifests remarkable hydrogen evolution reaction(HER)activity with low overpotentials of 55 and 225 mV at 10 and 200 mA·cm^(−2),which is superior to the FeNi-P(82 mV@10 mA·cm^(−2)and 301 mV@200 mA·cm^(−2)),and even out-performing the Pt/C catalyst at a high current density>200 mA·cm^(−2).Moreover,the oxygen evolution reaction(OER)activity of Zn-FeNi-P also has dramatically improved(207 mV@10 mA·cm^(−2))comparable to FeNi-P(221 mV@10 mA·cm^(−2))and RuO_(2)(239 mV@10 mA·cm^(−2)).Noticeably,an electrolyzer based on Zn-FeNi-P electrodes requires a low cell voltage of 1.47 V to achieve 10 mA·cm^(−2),far beyond the catalytic activities of FeNi-P||FeNi-P(1.51 V@10 mA·cm^(−2))and the benchmark RuO_(2)||Pt/C couples(1.56 V@10 mA·cm^(−2)).This Zn-implanting strategy paves a new perspective for the development of admirable bifunctional catalysts.

Wavelength-dependent nonlinear absorption of gold nanocages

The dipole resonances of gold nanocages were investigated theoretically using finite difference time domain method.The results show that field enhancement is obtained at the walls of the gold nanocages.It is believed that the effect can cause a strong optical nonlinear property.To test the hypothesis,nonlinear absorption was investigated using a broadband 5 ns Z scan.It was found that at low intensities the sample shows saturable absorption(SA),while at higher intensities a switch from SA to reverse SA occurs.Moreover,the nonlinear absorption of the sample is sensitively wavelength-dependent,and,in the resonant region,saturation intensity is the largest.

The effect of Coulomb interaction on particle-antiparticle correlation function

Dear Editors,The quantitative interpretation of the particle and antiparticle correlation results depends critically on understanding the role of Coulomb interaction of the measured pairs of particles with each other,as well as the Coulomb interaction of the pair with the system of remaining particles[1-7].

Dynamic Study of Nonlinear Optical Properties in Tetrasodium Salt of Copper Tetrasulfophthalocyanine/Water Solution

The nonlinear refraction of tetrasodium salt of copper tetrasulfophthalocyanine in water was investigated by using Z-scan technique at 532 nm with different input energy and different pulse width. We reported the competition between the excited-state refraction and excited-state-thermal-induced refraction. The sign change of nonlinear refraction induced by thermal effect was observed and analyzed. In addition, we found that the excited-state refraction cannot counteract with excited-state-thermal-induced refraction due to different physical mechanism.

Subwavelength metal structures with tunable transmission characteristics by light

Extraordinary optical transmission(EOT)in subwavelength metal structures has been studied widely.Herein,we propose a strategy for tuning the EOT of the bullseye structure.Specifically,the bullseye structure was immersed in a nonlinear medium,and a controlling light was employed to change the refractive index of the medium.At different intensities and distributions of controlling light,the transmission property of signal light in the bullseye structure was simulated.The results show that a variable transmission spectrum in the bullseye structure can be realized.Moreover,the position of the central transmission peak shifts linearly with the increasing intensity of controlling light.

Switchable optical nonlinear properties of W_(18)O_(49) nanowires by Ag nanoparticles supported

During the past decades,nonlinear optical（NLO）materials have attracted special interest because of their potential applications in photonic devices,such as optical switching,frequency conversion and electro-optic modulators.Among the finding ways to obtain excellent NLO materials with both large NLO response and short response time,