Journal of Science: Advanced Materials and Devices (2016) 200e203 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original article Synthesis of ZnS:MneFe3O4 bifunctional nanoparticles by inverse microemulsion method Chu Tien Dung a, b, Luu Manh Quynh a, Nguyen Phuong Linh a, Nguyen Hoang Nam a, c, *, Nguyen Hoang Luong c a b c Faculty of Physics, Hanoi University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Hanoi, Viet Nam University of Transport and Communications, Cau Giay, Hanoi, Viet Nam Nano and Energy Center, Hanoi University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Hanoi, Viet Nam a r t i c l e i n f o a b s t r a c t Article history: Received 31 May 2016 Accepted 10 June 2016 Available online 17 June 2016 ZnS:MneFe3O4 bifunctional nanoparticles were synthesized by inverse microemulsion method for biomedicine applications The bifunctional nanoparticles were combined from prepared ZnS:Mn and Fe3O4 nanoparticles in a SiO2 cover matrix Results show that bifunctional nanoparticles, apart from exhibiting magnetism, have photoluminescence properties, which support the applications targeting biomedicine fluorescent diagnostics as well as magnetic cell sorting or drug delivery © 2016 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: ZnS:Mn Fe3O4 Bifunctional nanoparticles Magnetic materials Inverse microemulsion Introduction Multifunctional nanoparticles are of a great interest in recent development due to the growing needs in biomedical applications They have potential to integrate various functionalities such as providing contrast for labeling agent, image-guided therapies, targeted drug delivery, thermal therapies or simultaneously serve as magnetic separator [1e4] At the beginning, core-shell structures were considered to improve appropriate physical as well as chemical properties and combine them in one nanoparticle Advanced polymer coating such as polyethylene glycol was usually used as functionalizing agent to make the nanoparticles have good bio-compatibility [5e9] Some semiconductor coatings have been developed as photoluminescent shell to increase the luminescence [10e12] as well as making a cover against the toxic element release from core material, such as Se, Cd [11] In some other applications, metal and silica shells were coated for protecting the core materials [13,14] However, the synthesis method of core-shell structure referred tight conditions and expertise laboratory craftsmanship In this paper, a simple method of inversed microemulsion was * Corresponding author Faculty of Physics, Hanoi University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Hanoi, Viet Nam E-mail address: namnh@hus.edu.vn (N.H Nam) Peer review under responsibility of Vietnam National University, Hanoi used to prepare new bifunctional nanoparticles ZnS:MneFe3O4 from individual Mn-doped ZnS (ZnS:Mn) semiconductor nanoparticles and Fe3O4 magnetic nanoparticles in SiO2 coating matrix ZnS:Mn semiconductor nanoparticles can be employed for labeling of clinical tumor tissues [15] The magnetic nanoparticles with superparamagnetic properties can be used as targeted delivery of drug and/or gene, magnetic separation as well as magnetic therapies [16e19] The designed bifunctional nanoparticles can act similar functions like core-shell structure nanoparticles, providing simultanously photoluminescence as labeling agent in biomedical application, biocompatible and can be also purified by magnetic separator or can be used for drug delivery due to their magnetism, event under the coating of SiO2 matrix Experimental 2.1 Synthesis of ZnS:Mn nanoparticles ZnS:Mn nanoparticles were synthesized by ultrasound-assisted co-precipitation method using sodium sulphide (Na2S) as SÀ2 ion source ZnCl2 0.5 M were mixed with surfactance sodium dodecyl sulfate (SDS), CH3(CH2)11SO4Na) 0.25 M and Mn(CH3COO)2 0.5 M to get precursor solution The molar ratio of Mn/Zn was 1/10 This solution was ultrasonicated with the pulse mode on:off being 2s:2s The ultrasonic power and the frequency was 225 W and http://dx.doi.org/10.1016/j.jsamd.2016.06.006 2468-2179/© 2016 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) C.T Dung et al / Journal of Science: Advanced Materials and Devices (2016) 200e203 201 20 kHz, respectively During the ultrasonicating, Na2S solution was slowly added into the precursor solution After h, the ZnS:Mn nanoparticles were collected by washing times with distilled water before being dispersed in isopropanol 2.2 Synthesis of Fe3O4 nanoparticles Fe3O4 nanoparticles were synthesized by co-precipitation method [20,21] using Fe2ỵ/Fe3ỵ with 1:2 M ratios from the two chloride salts of FeCl2 and FeCl3, which were diluted to 0.01 M/ 0.02 M concentration The mixed solution was vigorously stirred and kept at 60 C before NH4OH 30% was being added to have the black color precipitation The final solution was purified by magnetic separation with ethanol and distilled water several times to decontaminate the auxiliary chemicals Fe3O4 nanoparticles, then, were dispersed in isopropanol 2.3 Synthesis of ZnS:MneFe3O4 bifunctional nanoparticles The bifunctional nanoparticles were combined from above two kinds of nanoparticles by inverse microemulsion method The inverse microemulsion was created by mixing hydrophobic phase of toluene and hydrophilic phase that was made from the mixture of ZnS:Mn solution and Fe3O4 solution in isopropanol right after synthesis and the solution of NH4OH with distilled water Under sonic bath, tethraethylorthosilicate (TEOS) was added to react with water in solution to form amorphous SiO2 matrix that covered both types of particles The morphology of the ZnS:Mn, Fe3O4 and the ZnS:MneFe3O4 nanoparticles was investigated by transmission electron microscope (TEM, JEOL- JEM1010) The structure of nanoparticles was studied using X-ray diffractormeter (XRD, Bruker D5005) The average crystallite size, d, is calculated from the line broadening using Scherrer's formula: d ¼ 0.9l/(Bcosq), where B is the half maximum line width and l is the wavelength of X-rays The chemical composition of the nanoparticles was studied by using an energy dispersion spectroscopy (EDS) included in JEOL 5410LV scanning electron microscope and the chemical bonding was investigated by using Fourier Transformation Infra-Red (FTIR 6300, Shimadzu) absorption Magnetic properties of samples were studied by using DMS 880 Vibrating Sample Magnetometer (VSM) with a maximum magnetic field of 13.5 kOe at room temperature Optical properties of sample were investigated by using the Flourolog FL 3-22 photoluminescence (PL) spectroscopy (Jobin e Yvon e Spex, USA) Results and discussion Fig shows the TEM images of the ZnS:Mn, Fe3O4, and the ZnS:MneFe3O4 nanoparticles The TEM image of ZnS:Mn does not show very clear shape of nanoparticles, that may be due to the amorphous cover of synthesized nanoparticles The TEM image of the Fe3O4 nanoparticles shows well-dispersed nanoparticles with size of about 15 nm The TEM image of the ZnS:MneFe3O4 nanoparticles shows the colloids with the mean size of around 45 nm and does not show small colloids of around 15 nm and nm, which are typical sizes of Fe3O4 and ZnS:Mn nanoparticles, respectively The ZnS:MneFe3O4 nanoparticles contain ZnS:Mn and Fe3O4 nanoparticles inside This microstructure of the ZnS:MneFe3O4 nanoparticles is supported by the results of measurements discussed below The XRD patterns of the Fe3O4, ZnS:Mn and ZnS:MneFe3O4 nanoparticles are shown in Fig The pattern of the coprecipitation synthesized Fe3O4 nanoparticles is characteristic of the Fe3O4 structure with diffraction peaks at 30.1, 36.0 , 43.9 , Fig TEM images of (a) ZnS:Mn, (b) Fe3O4 and (c) ZnS:MneFe3O4 nanoparticles 63.1 which can be assigned with (200), (311), (400), 53.6 , 57.5 va (440) reflections, respectively Fe3O4 nanoparticles (422), (511) va have an inverse spinel structure with oxygen forming facecentered cubic (fcc) structure with F3dm space group From diffraction peaks we obtained the lattice parameter of 8.36 ± 0.04 Å Using Scherrer's formula, the particle size was estimated to be around 10 nm The pattern of the synthesized ZnS:Mn nanoparticles shows diffraction peaks at 29.1, 48.1, 57.5 202 C.T Dung et al / Journal of Science: Advanced Materials and Devices (2016) 200e203 Fig X-ray patterns of ZnS:Mn, Fe3O4 and ZnS:MneFe3O4 nanoparticles They can be ascribed as (111), (200), (220) reflections, respectively The obtained lattice parameter of 5.32 ± 0.02 Å for fcc structure and the particle size was estimated to be around 4.7 nm, in agreement with particles size observed by TEM image The XRD pattern of the combined ZnS:MneFe3O4 nanoparticles shows typical amorphous structure of SiO2 coated matrix with the sign of the (311), (400), (422), (511) reflections of Fe3O4 structure and the weaker (200), (220) reflections of ZnS:Mn structure The SiO2 cover could absorb X-ray, leading to the disappearance of some XRD peaks of ZnS:Mn and Fe3O4 nanoparticles The FTIR absorption spectra of the Fe3O4, ZnS:Mn and the ZnS:MneFe3O4 nanoparticles are shown in Fig All the spectra show the broad peaks at 3400 cmÀ1 of OeH stretching vibration [22] and the peaks at 1628, 2340, 2361 cmÀ1 which can be assigned to CeO vibration of CO2 [22,23] related to the air background of the measurement These peaks are due to the presence of CO2 and H2O in all the samples The spectrum of ZnS:MneFe3O4 shows typical absorption peaks of ZnS:Mn such as peaks at 1106, 617 and 465 cmÀ1 of ZneS bonding or peak at 1174 cm1 which appears when Mn2ỵ is doped into ZnS crystal [24] The two peaks Fig FTIR spectra of ZnS:Mn, Fe3O4 and ZnS:MneFe3O4 nanoparticles at 2851 and 2924 cmÀ1, which appear both in ZnS:Mn and ZnS:MneFe3O4 samples, are due to the microstructure formation of ZnS:Mn nanoparticles [24] The spectrum of ZnS:MneFe3O4 also shows typical absorption peaks of Fe3O4 nanoparticles such as peak at 560 cmÀ1 of FeeO vibration [25] Furthermore, this spectrum has peaks of SiO2 such as peaks at 797 cmÀ1 and 960 cmÀ1 [26,27] These results and the XRD results support that the ZnS:MneFe3O4 nanoparticles were successfully combined from ZnS:Mn and Fe3O4 nanoparticles in SiO2 matrix Fig shows the PL spectrum of ZnS:Mn and that of ZnS:MneFe3O4 nanoparticles excited at 335 nm The spectrum of ZnS:Mn nanoparticles have the peak at 438 nm which is originated from defects caused by missing of some Zn ion in ZnS crystal structure, and the peak at 595 nm which is originated from the T1/6A1 transition in 3d5 electronic layer of Mn2ỵ ion [28e30] The spectrum of ZnS:MneFe3O4 nanoparticles also has two photoluminescence peaks, one at 595 nm and the other at 425 nm, similar to that of ZnS:Mn However the intensity of the peak at 595 nm of ZnS:MneFe3O4 nanoparticles is lower than that of ZnS:Mn nanoparticles This can be explained by the presence of Fe3O4 and SiO2 in ZnS:MneFe3O4 nanoparticles, which reduces the inuence of Mn2ỵ ion on PL result These results indicate that ZnS:MneFe3O4 nanoparticles contain ZnS:Mn nanoparticles and have similar PL properties with ZnS:Mn nanoparticles in visible region, which can be used for labeling application in biomedicine Fig shows magnetization curves measured on the ZnS:Mn, Fe3O4 and ZnS:MneFe3O4 nanoparticles It can be seen that the magnetization of ZnS:Mn nanoparticles is very low, of emu/g, compared to those of Fe3O4 and ZnS:MneFe3O4 nanoparticles, which reaches around 59.4 emu/g and 31.7 emu/g at 13.5 kOe, respectively The fact that the ZnS:MneFe3O4 nanoparticles have lower magnetization can be explained by the presence of ZnS:Mn nanoparticles inside the sample as well as the presence of the SiO2 cover matrix which does not exhibit magnetism The ZnS:MneFe3O4 nanoparticles show magnetic properties similar to Fe3O4 nanoparticles, indicating that the synthesized ZnS:MneFe3O4 nanoparticles contain Fe3O4 nanoparticles inside Fig Photoluminescence spectra of ZnS:MneFe3O4 and ZnS:Mn nanoparticles excited at 335 nm C.T Dung et al / Journal of Science: Advanced Materials and Devices (2016) 200e203 Fig The magnetization curves of ZnS:Mn, Fe3O4 and ZnS:MneFe3O4 nanoparticles at room temperature These results also support the successful combining of Fe3O4 and ZnS:Mn nanoparticles in SiO2 matrix The magnetic properties of nanoparticles investigated also show that ZnS:MneFe3O4 nanoparticles can be used for magnetic delivery, therapies or DNA separating applications in biomedicine Conclusions ZnS:MneFe3O4 bifunctional nanoparticles were successfully synthesized from ZnS:Mn and Fe3O4 nanoparticles in biocompatible SiO2 matrix using inverse microemulsion method The bifunctional nanoparticles have photoluminescence similar to ZnS:Mn photoluminescence nanoparticles and magnetic propeties similar to Fe3O4 magnetic nanoparticles, which support their use in both labeling and separating applications in biomedicine Furthermore, with the biocompartible SiO2 cover matrix, these nanoparticles can be easily surface-modified in many biomedicineapplication purposes Acknowledgment This paper is dedicated to the memory of Peter Brommer He was a good friend of the Vietnamese physicists during the years of cooperation between the Hanoi and Amsterdam Universities With his deep knowledge of 'Magnetism of Metals' he was always ready to assist his colleagues We are grateful for his involvement in the cooperation over a period as long as thirty years References [1] G Bao, S Mitragotri, S Tong, Multifunctional nanoparticles for drug delivery 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inuence of Mn2 ỵ... measured on the ZnS: Mn, Fe3O4 and ZnS: MneFe3O4 nanoparticles It can be seen that the magnetization of ZnS: Mn nanoparticles is very low, of emu/g, compared to those of Fe3O4 and ZnS: MneFe3O4 nanoparticles, ... support that the ZnS: MneFe3O4 nanoparticles were successfully combined from ZnS: Mn and Fe3O4 nanoparticles in SiO2 matrix Fig shows the PL spectrum of ZnS: Mn and that of ZnS: MneFe3O4 nanoparticles