| Photocatalysts have piqued the interest of researchers due to their potential to solve the global energy crisis.Tin dioxide(Sn O2)has been widely used in environmental science and energy because of its advantages in film formation,stability,high oxidation potential,non-toxicity,corrosion resistance,and high economic benefits.However,the photocatalytic efficiency of single Sn O2falls far short of practical requirements,which is primarily due to its inherent physical properties:(i)Due to Sn O2's wide bandgap of about 3.6 e V,it absorbs only ultraviolet light,resulting in extremely low utilization of sunlight;(ii)Severe recombination of photogenerated electrons and holes in Sn O2.The localized surface plasmon resonance(LSPR)effect of noble metal nanoparticles is critical in improving semiconductor optoelectronic properties.By adjusting the particle size of noble metal nanoparticles,it can achieve full-band absorption of visible light,significantly improving the utilization of visible light by semiconductors.At the same time,the solid localised electromagnetic field formed by the localized surface plasmon resonance around the noble metal nanoparticles can promote energy transfer to the semiconductor.The separation rate of electrons and holes in the semiconductor is greatly improved,which further enhances the photocatalytic effect of the semiconductor material.The LSPR effect of noble metal nanoparticles strengthens the optoelectronic properties of semiconductor materials as an emerging research field.Its potential enhancement mechanism has not been investigated,which will undoubtedly have implications for the design of ultra-efficient semiconductor photocatalysts.Taking into consideration the aforementioned relevant issues,we investigated tin dioxide's photoelectric performance enhancement mechanism induced by LSPR by ingeniously designing the metal/semiconductor research model.We confirmed the contribution of the localized electromagnetic field generated by the surface plasmon resonance effect of noble metal nanoparticles to improving semiconductor optoelectronic properties.We dug deeper into the connection between LSPR-mediated direct electron transfer and local electromagnetic fields.Finally,we developed a new composite nanomaterial based on the enhancement mechanisms we investigated.This composite material achieves effective organic pollutant monitoring and degradation.Considering the above scientific problems,we studied tin dioxide's photoelectric performance enhancement mechanism induced by LSPR by ingeniously designing the metal/semiconductor research model.We confirmed the contribution of the localized electromagnetic field brought by the surface plasmon resonance effect of noble metal nanoparticles to improving semiconductor optoelectronic properties.We further explored the relationship between LSPR-mediated direct electron transfer and local electromagnetic fields.Finally,we prepared a new composite nanomaterial based on these studied enhancement mechanisms.This composite material effectively monitors and degrades organic pollutants.The following is the specific work content:1.The effect of localized electromagnetic field mediated by noble metal surface plasmon resonance on the Photoelectric properties of Au@SiO2/Sn O2We created Au@SiO2/Sn O2noble metal-semiconductor composite nanomaterials to explore the effect of surface plasmon resonance effect-mediated localized electromagnetic field(LEMFE)in improving semiconductor photocatalytic performance.The gold nanoparticles in this composite nanomaterial are completely covered by a dense silica layer,preventing direct contact between the noble metal nanoparticles and the semiconductor.The silicon dioxide layer prevents direct electron transfer(DET)between metal and semiconductors.Furthermore,transmission electron microscopy characterization reveals that the gold core size in the Au@SiO2core-shell structure is approximately 30 nm,ensuring that the light scattering enhancement is very weak.There was no spectral overlap between the resonance bands of plasmonic nanoparticles and the absorption bands of semiconductors in the UV-Vis absorption spectra,indicating the absence of plasmon-induced resonance energy transfer(PIRET)between nanomaterials.We discovered that the Au@SiO2/Sn O2composite nanomaterials could efficiently degrade methyl orange(MO)when exposed to visible light in the following photocatalytic degradation experiments.We conclude that the localized electromagnetic field mediated by the surface plasmon resonance of gold nanoparticles promotes the separation of electron-hole pairs in the semiconductor.As a result,the semiconductor has exceptional photocatalytic performance.The presence of a localized electromagnetic field(LEMF)was confirmed by transient photocurrent,and its intensity increased with increasing illumination intensity.2.Investigating the relationship between direct electron transfer and local electromagnetic fields in enhancing semiconductor optoelectronic properties.We investigate the relationship between local electromagnetic fields and direct electron transfer mediated by noble metal surface plasmon resonance in enhancing the optoelectronic properties of semiconductors by comparing the photocatalytic properties of Au/Sn O2and Au@SiO2/Sn O2.The noble metal nanoparticles in the Au/Sn O2nanocomposite come into contact with the semiconductor.As a result,when exposed to visible light,there are two energy transfer modes between gold nanoparticles(Au NPs)and Sn O2:direct electron transfer and local electromagnetic field enhancement.However,the direct electron transfer path is entirely shielded in the Au@SiO2/Sn O2system because the dense silica(SiO2)film completely encapsulates the Au NPs core.So there is only an enhancement of LEMFE between the metal and the semiconductor.By studying the fitted first-order kinetic model of MO degradation,we found that the rate constant of Au@SiO2/Sn O2is two times higher than that of Au/Sn O2.The experimental phenomenon shows that the Au@SiO2/Sn O2nanocomposites with only LEMFE have better photocatalytic performance.Therefore,we infer that in the Au/Sn O2system,DET and LEMFE are not synergistic but antagonistic.In other words,DET can suppress the semiconductor-enhanced photocatalytic performance of LEMFE.The consistent results of photodetection and photocatalytic degradation further support our inference.The results reveal the versatility of noble metal nanoparticles in enhancing the photocatalytic performance of semiconductors.The experimental results have guiding significance for preparing metal-semiconductor nanocomposites and their application in photocatalysis.3.Efficient visible light degradation of chlortetracycline by Ti O2/Sn O2/Au@SiO2compositesTo further improve the semiconductor photocatalytic performance,we synthesized Ti O2/Sn O2/Au@SiO2heterojunction photocatalysts with innovative morphology and appropriate bandgap structure.To solve the problems of low photon absorption efficiency and high carrier recombination rate of single Sn O2,we constructed Sn O2/Ti O2heterojunction according to the energy band characteristics of Sn O2.The photocatalytic degradation results show that the photocatalytic activity of the Ti O2/Sn O2/Au@SiO2composite nanomaterial is increased by 1.7 times compared with Sn O2/Au@SiO2without semiconductor-semiconductor heterostructure.It shows that the existence of heterojunction can effectively reduce the recombination rate of photogenerated carriers.In addition,we found that in the photocatalytic degradation of chlortetracycline,the photocatalytic activities of the composite nanomaterials Sn O2/Au@SiO2and Ti O2/Au@SiO2were 14 times and nine times higher than that of single Sn O2and Titanium dioxide(Ti O2)respectively.We speculate that the core-shell structure of Au@SiO2NPs is excited by visible light to generate a solid local electromagnetic field.The local electromagnetic field of Au@SiO2NPs acting on nearby semiconductors(Sn O2,Ti O2)can improve the electron-hole separation rate in the semiconductor,increase the concentration of photogenerated carriers,and promote the photocatalytic process. |
PDF Full Text Request