| Most environmental pollutants,such as heavy metals and organics,exist in the form of trace or ultra-trace amounts.Traditional detection techniques are often time-consuming and less sensitivity.Surface enhanced Raman scattering?SERS?is a highly sensitive and nondestructive analysis and detection tool that can meet the requirements of single molecular level trace detection.However,most SERS substrates are noble metals,which are high cost,complex process and difficult to clean and recycle.In addition,the degradation of pollutants has been a hot field for researchers.Photocatalytic degradation is a fast,cheap and energy efficient method in many degradation methods.In recent years,some ferrites have been proved to be better visible photocatalyst to degrade organic pollutants.Reasonable design can improve the versatility,degradation efficiency and reduce the cost of treating pollutants.Therefore,this paper studied the preparation of four ferrites in nanometer scale with improved method to form Ag ferrites nano composites.The obtained nano composites have both SERS performance and photocatalytic activity,it can detect and degrade pollutants,which greatly improves the practical application value of these spinel oxides.The main results of this paper are as follows:?1?MnFe2O4 nanoparticles were successfully prepared by low-temperature hydrothermal method,and the particle size was about 60 nm.Ag nanoparticles were load on the surface of MnFe2O4 to form Ag/MnFe2O4 nanocomposite by photochemical reduction method.The composite material exhibits excellent SERS performance,with a detection line of 10-9mol·L-1 and EF of 6.93×106 for Rhodamine R6?R6G?.Photocatalytic experiments show that 99.68%of R6G is degraded in 100 minutes using the nanocomposite as catalyst in the presence of H2O2.In addition,the cyclic stability of Ag/MnFe2O4 composite nanomaterials as a SERS substrate has also been studied.After three cycles,the enhancement factor for R6G is still up to 3.72×104.This nanocomposite material can be used as both a SERS substrate and a photocatalyst.Through the photocatalytic process,it can promote the cleaning and recycling of SERS substrates,realize rapid detection of organic pollutants and effective photocatalytic degradation.?2?ZnFe2O4 nanoparticles were successfully prepared by low-temperature hydrothermal method and calcining process,and the particle size was about 30 nm.Ag nanoparticles were formed on ZnFe2O4 surface by photochemical reduction method to form Ag/ZnFe2O4nanocomposites.The obtained nanocomposite nanomaterials showed excellent SERS performance,with a detection line of 10-8 mol·L-1 and EF of 4.1×106 for R6G.Photocatalytic experiments show that 97.56%of R6G is degraded in 90 minutes using the nanocomposite as catalyst in the presence of H2O2.In addition,Ag/ZnFe2O4 can be used as a reusable SERS substrate.After three cycles,the EF value still reaches 4.5×104 for R6G.?3?NiFe2O4 nanoparticle arrays on carbon fiber cloth have been successfully fabricated by a hydrothermal route followed by a calcination treatment.Then,Ag nanoparticles was loaded on the surface of the obtained NiFe2O4 nanoparticle arrays by photochemical reduction method to form Ag/NiFe2O4 composite nanomaterials.The composite material exhibits excellent SERS performance,with a detection line of 10-9 mol·L-1 and EF of 9.55×106 for R6G.The SERS signals collected 16 points over a 20?m×20?m area show relative standard deviation lower than 12%,suggesting good SERS signal uniformity.In addition,the Ag/NiFe2O4 composite nanomaterials can be used as an effective photo-Fenton catalyst photocatalytical degradation of R6G under the condition of H2O2.It was found that 98.55%of 50 mL 5 mg·L-1 R6G solution can be degraded in 70 mins.The experiment also explored the effect of photochemical reduction time on the particle size and SERS performance of Ag nanoparticles,and plotted the particle size distribution histogram.The experimental results show that with the extension of the illumination time,the formed Ag nanoparticle is more densely distributed,and the Ag nanoparticles become larger,from the original irregularity into a polygon,and with the extension of the illumination time,the SERS performance gradually declines.?4?CoFe2O4/Fe2O3 nanorod arrays on carbon fiber cloth have been successfully fabricated by a hydrothermal route followed by a calcination treatment.The nanorod arrays grow uniformly and densely on the surface of carbon cloth with a diameter of 40-90 nm.Through the photochemical reduction process,Ag nanoparticles were successfully loaded on the surface of CoFe2O4/Fe2O3 substrates to form Ag@CoFe2O4/Fe2O3 composite nanorod arrays.The Ag nanoparticles with a size of 10-40 nm are spatially uniformly distributed on the CoFe2O4/Fe2O3 nanorod arrays.The obtained Ag@CoFe2O4/Fe2O3 nanorod arrays show excellent SERS performance,which provides enhancement factors?EF?as high as about1.2×108 and the detection line is low to 10-10 mol·L-1 for R6G.The SERS signals collected over a 20?m×20?m area show relative standard deviation lower than 12%,suggesting good SERS signal uniformity.In addition,the Ag@CoFe2O4/Fe2O3 nanorod arrays can be used as an effective photo-Fenton catalyst photocatalytical degradation of R6G.It was found that 99.15%of R6G can be degraded in an hour in the presence of H2O2.In addition,the Ag@CoFe2O4/Fe2O3 substrate can be used as a recyclable Raman substrate,and the enhancement factor still reaches 2.0×104 after five cycles. |
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