Bloch surface waves(BSWs) are excited in one-dimensional photonic crystals(Ph Cs) terminated by a graphene monolayer under the Kretschmann configuration. The field distribution and reflectance spectra are numerically ...Bloch surface waves(BSWs) are excited in one-dimensional photonic crystals(Ph Cs) terminated by a graphene monolayer under the Kretschmann configuration. The field distribution and reflectance spectra are numerically calculated by the transverse magnetic method under transfer-matrix polarization, while the sensitivity is analyzed and compared with those of the surface plasmon resonance sensing method. It is found that the intensity of magnetic field is considerably enhanced in the region of the terminated layer of the multilayer stacks, and that BSW resonance appears only in the interface of the graphene and solution. Influences of the graphene layers and the thickness of a unit cell in Ph Cs on the reflectance are studied as well. In particular, by analyzing the performance of BSW sensors with the graphene monolayer,the wavelength sensitivity of the proposed sensor is 1040 nm/RIU whereas the angular sensitivity is 25.1?/RIU. In addition,the maximum of figure of merit can reach as high as 3000 RIU-1. Thus, by integrating graphene in a simple Kretschmann structure, one can obtain an enhancement of the light–graphene interaction, which is prospective for creating label-free,low-cost and high-sensitivity optical biosensors.展开更多
Dioxin is a highly toxic and caustic substance,which widely existed in the atmosphere,soil and water with tiny particles.Dioxin pollution has become a major problem that concerns the survival of mankind,which must be ...Dioxin is a highly toxic and caustic substance,which widely existed in the atmosphere,soil and water with tiny particles.Dioxin pollution has become a major problem that concerns the survival of mankind,which must be strictly controlled.The bond length,bond angle,energy,dipole moment,orbital energy level distribution of dioxin under the external field are investigated using DFT(density functional theory)on basis set level of B3LYP/6-31G(d,p).The results indicate that with the increase of the electric field,the length of one Carbon-Oxygen bond increases while another Carbon-Oxygen bond decreases.The energy gradually decreases with the electric field,while the change of the dipole moment has an opposite trend.In the infrared spectra,the vibration frequency decreases with the electric field increasing and shows an obvious red shift.Moreover,the ultraviolet-visible absorption spectra under different electric fields are analyzed with TD-DFT(time-dependent density functional theory)method.The wavelength of the strongest absorption peak increases and occurs red shift with the increase of the electric field.All the above results can provide reference for further research on the properties of dioxin under different external electric field.展开更多
Ultrafast dissociation dynamics of chloroiodomethane(CH_2ICl)in the B band is studied by femtosecond timeresolved time-of-flight(TOF)mass spectrometry.Time-resolved TOF mass signal of parent ion(CH_2ICl^+)and main dau...Ultrafast dissociation dynamics of chloroiodomethane(CH_2ICl)in the B band is studied by femtosecond timeresolved time-of-flight(TOF)mass spectrometry.Time-resolved TOF mass signal of parent ion(CH_2ICl^+)and main daughter ion(CH_2 Cl^+)are obtained.The curve for the transient signal of CH_2ICl^+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function.The decay constant determined to be less than 35 fs reflects the lifetime of the B band.Significant substituent effects on photodissociation dynamics of CH_2ICl compared with CH3I are discussed.The dissociation time from the parent ion CH_2ICl^+ to the daughter ion CH_2 Cl^+ is determined in the experiment.The optimized geometry of the ionic state of CH_2ICl and the ionization energy are calculated for further analysis of the measurements.In addition,compared with the parent ion,a new decay component with time constant of ~596 fs is observed for CH_2 Cl^+,and reasonable mechanisms are proposed for the explanation.展开更多
Narrow band mid-infrared(MIR)absorption is highly desired in thermal emitter and sensing applications.We theoretically demonstrate that the perfect absorption at infrared frequencies can be achieved and controlled aro...Narrow band mid-infrared(MIR)absorption is highly desired in thermal emitter and sensing applications.We theoretically demonstrate that the perfect absorption at infrared frequencies can be achieved and controlled around the surface phonon resonance frequency of silicon carbide(SiC).The photonic heterostructure is composed of a distributed Bragg reflector(DBR)/germanium(Ge)cavity/SiC on top of a Ge substrate.Full-wave simulation results illustrate that the Tamm phonon-polaritons electric field can locally concentrate between the Ge cavity and the SiC film,contributed to the improved light-phonon interactions with an enhancement of light absorption.The structure has planar geometry and does not require nano-patterning to achieve perfect absorption of both polarizations of the incident light in a wide range of incident angles.Their absorption lines are tunable via engineering of the photon band-structure of the dielectric photonic nanostructures to achieve reversal of the geometrical phase across the interface with the plasmonic absorber.展开更多
Isomers are widely present in volatile organic compounds(VOCs),and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere.In this work,laserinduced breakdown spectroscopy(LIBS)techno...Isomers are widely present in volatile organic compounds(VOCs),and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere.In this work,laserinduced breakdown spectroscopy(LIBS)technology was developed to online distinguish VOCs and their isomers in the air.First,LIBS was used to directly detect halogenated hydrocarbons(a typical class of VOCs)and the characteristic peaks of the related halogens were observed in the LIBS spectra.Then,comparing the LIBS spectra of various samples,it was found that for VOCs with different molecular formulas,although the spectra are completely the same in elemental composition,there are still significant differences in the relative intensity of the spectral lines and other information.Finally,in light of the shortcomings of traditional LIBS technology in identifying isomers,machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs,and the recognition results were very good.It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.展开更多
Bubble evolution in low energy and high dose He-implanted 6 H-SiC upon thermal annealing is studied. The(0001)-oriented 6 H-SiC wafers are implanted with 15 keV helium ions at a dose of 1×10^(17) cm^(-2) at room ...Bubble evolution in low energy and high dose He-implanted 6 H-SiC upon thermal annealing is studied. The(0001)-oriented 6 H-SiC wafers are implanted with 15 keV helium ions at a dose of 1×10^(17) cm^(-2) at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473 K for30 min. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy(XTEM)analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6 H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273 K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases.The growth of He bubbles after high temperature annealing abides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914+0.236 eV.展开更多
A concentration sensor based on silver(Ag)/silica(SiO2)/zirconium anhydride(ZrO2)multilayer structure is proposed.Two dominant dips can be observed in the reflection spectrum,which correspond to different sensing meth...A concentration sensor based on silver(Ag)/silica(SiO2)/zirconium anhydride(ZrO2)multilayer structure is proposed.Two dominant dips can be observed in the reflection spectrum,which correspond to different sensing methods.Firstly,it is demonstrated that the coupling between the surface plasmon polariton(SPP)mode and a planar waveguide mode(WGM)leads to the Fano resonance(FR).The induced bonding hybridized modes have ultra-narrow full wave at half maximum(FWHM)as well as ultra-high quality factors(Q).We can achieve a theoretical value of the refractive index sensitivity 167 times higher than conventional surface plasmon resonance(SPR)sensors with a single metal layer.Secondly,the waveguide coupling mode was examined by measuring angular spectra.A deep and sharp waveguide coupling dip was obtained.The experimental results show that with an increase in the concentration of the fill dielectric material in the surface of the system,the resonance dip exhibits a remarkable red shift,and the measured angular sensitivity is 98.04°/RIU.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61203211 and 41675154)the Six Major Talent Peak Expert of Jiangsu Province,China(Grant No.2015-XXRJ-014)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20141483)
文摘Bloch surface waves(BSWs) are excited in one-dimensional photonic crystals(Ph Cs) terminated by a graphene monolayer under the Kretschmann configuration. The field distribution and reflectance spectra are numerically calculated by the transverse magnetic method under transfer-matrix polarization, while the sensitivity is analyzed and compared with those of the surface plasmon resonance sensing method. It is found that the intensity of magnetic field is considerably enhanced in the region of the terminated layer of the multilayer stacks, and that BSW resonance appears only in the interface of the graphene and solution. Influences of the graphene layers and the thickness of a unit cell in Ph Cs on the reflectance are studied as well. In particular, by analyzing the performance of BSW sensors with the graphene monolayer,the wavelength sensitivity of the proposed sensor is 1040 nm/RIU whereas the angular sensitivity is 25.1?/RIU. In addition,the maximum of figure of merit can reach as high as 3000 RIU-1. Thus, by integrating graphene in a simple Kretschmann structure, one can obtain an enhancement of the light–graphene interaction, which is prospective for creating label-free,low-cost and high-sensitivity optical biosensors.
基金The project is supported by Natural Science Foundation of Xinjiang(No.2017D01B36).
文摘Dioxin is a highly toxic and caustic substance,which widely existed in the atmosphere,soil and water with tiny particles.Dioxin pollution has become a major problem that concerns the survival of mankind,which must be strictly controlled.The bond length,bond angle,energy,dipole moment,orbital energy level distribution of dioxin under the external field are investigated using DFT(density functional theory)on basis set level of B3LYP/6-31G(d,p).The results indicate that with the increase of the electric field,the length of one Carbon-Oxygen bond increases while another Carbon-Oxygen bond decreases.The energy gradually decreases with the electric field,while the change of the dipole moment has an opposite trend.In the infrared spectra,the vibration frequency decreases with the electric field increasing and shows an obvious red shift.Moreover,the ultraviolet-visible absorption spectra under different electric fields are analyzed with TD-DFT(time-dependent density functional theory)method.The wavelength of the strongest absorption peak increases and occurs red shift with the increase of the electric field.All the above results can provide reference for further research on the properties of dioxin under different external electric field.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11304157,21303255 and 11475229the‘Six Talent Peaks’Project in Jiangsu Province under Grant No 2015-JNHB-011the College Students Practice Innovative Training Program of Nuist under Grant No 201610300042
文摘Ultrafast dissociation dynamics of chloroiodomethane(CH_2ICl)in the B band is studied by femtosecond timeresolved time-of-flight(TOF)mass spectrometry.Time-resolved TOF mass signal of parent ion(CH_2ICl^+)and main daughter ion(CH_2 Cl^+)are obtained.The curve for the transient signal of CH_2ICl^+ is simple and can be well fitted by an exponential decay convoluted with a Gaussian function.The decay constant determined to be less than 35 fs reflects the lifetime of the B band.Significant substituent effects on photodissociation dynamics of CH_2ICl compared with CH3I are discussed.The dissociation time from the parent ion CH_2ICl^+ to the daughter ion CH_2 Cl^+ is determined in the experiment.The optimized geometry of the ionic state of CH_2ICl and the ionization energy are calculated for further analysis of the measurements.In addition,compared with the parent ion,a new decay component with time constant of ~596 fs is observed for CH_2 Cl^+,and reasonable mechanisms are proposed for the explanation.
基金Project supported by the National Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20191396,BK20180784).
文摘Narrow band mid-infrared(MIR)absorption is highly desired in thermal emitter and sensing applications.We theoretically demonstrate that the perfect absorption at infrared frequencies can be achieved and controlled around the surface phonon resonance frequency of silicon carbide(SiC).The photonic heterostructure is composed of a distributed Bragg reflector(DBR)/germanium(Ge)cavity/SiC on top of a Ge substrate.Full-wave simulation results illustrate that the Tamm phonon-polaritons electric field can locally concentrate between the Ge cavity and the SiC film,contributed to the improved light-phonon interactions with an enhancement of light absorption.The structure has planar geometry and does not require nano-patterning to achieve perfect absorption of both polarizations of the incident light in a wide range of incident angles.Their absorption lines are tunable via engineering of the photon band-structure of the dielectric photonic nanostructures to achieve reversal of the geometrical phase across the interface with the plasmonic absorber.
基金supported by National Natural Science Foundation of China(No.U1932149)the Natural Science Foundation of Jiangsu Province(No.BK20191395)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province of China(No.18KJA140002)。
文摘Isomers are widely present in volatile organic compounds(VOCs),and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere.In this work,laserinduced breakdown spectroscopy(LIBS)technology was developed to online distinguish VOCs and their isomers in the air.First,LIBS was used to directly detect halogenated hydrocarbons(a typical class of VOCs)and the characteristic peaks of the related halogens were observed in the LIBS spectra.Then,comparing the LIBS spectra of various samples,it was found that for VOCs with different molecular formulas,although the spectra are completely the same in elemental composition,there are still significant differences in the relative intensity of the spectral lines and other information.Finally,in light of the shortcomings of traditional LIBS technology in identifying isomers,machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs,and the recognition results were very good.It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.
基金Supported by the National Natural Science Foundation of China under Grant No 11475229
文摘Bubble evolution in low energy and high dose He-implanted 6 H-SiC upon thermal annealing is studied. The(0001)-oriented 6 H-SiC wafers are implanted with 15 keV helium ions at a dose of 1×10^(17) cm^(-2) at room temperature. The samples with post-implantation are annealed at temperatures of 1073, 1173, 1273, and 1473 K for30 min. He bubbles in the wafers are examined via cross-sectional transmission electron microscopy(XTEM)analysis. The results present that nanoscale bubbles are almost homogeneously distributed in the damaged layer of the as-implanted sample, and no significant change is observed in the He-implanted sample after 1073 K annealing. Upon 1193 K annealing, almost full recrystallization of He-implantation-induced amorphization in 6 H-SiC is observed. In addition, the diameters of He bubbles increase obviously. With continually increasing temperatures to 1273 K and 1473 K, the diameters of He bubbles increase and the number density of lattice defects decreases.The growth of He bubbles after high temperature annealing abides by the Ostwald ripening mechanism. The mean diameter of He bubbles located at depths of 120-135 nm as a function of annealing temperature is fitted in terms of a thermal activated process which yields an activation energy of 1.914+0.236 eV.
基金supported by the National Science Foundation of China(No.41675154)the Natural Science Foundation of Jiangsu Province(No.BK20191396)。
文摘A concentration sensor based on silver(Ag)/silica(SiO2)/zirconium anhydride(ZrO2)multilayer structure is proposed.Two dominant dips can be observed in the reflection spectrum,which correspond to different sensing methods.Firstly,it is demonstrated that the coupling between the surface plasmon polariton(SPP)mode and a planar waveguide mode(WGM)leads to the Fano resonance(FR).The induced bonding hybridized modes have ultra-narrow full wave at half maximum(FWHM)as well as ultra-high quality factors(Q).We can achieve a theoretical value of the refractive index sensitivity 167 times higher than conventional surface plasmon resonance(SPR)sensors with a single metal layer.Secondly,the waveguide coupling mode was examined by measuring angular spectra.A deep and sharp waveguide coupling dip was obtained.The experimental results show that with an increase in the concentration of the fill dielectric material in the surface of the system,the resonance dip exhibits a remarkable red shift,and the measured angular sensitivity is 98.04°/RIU.
