Zn_(1-x)Mn_xS稀磁半导体的合成与光学性能

通过水热法制备不同掺杂浓度的Zn_(1-x)Mn_xS(x=0.00,0.02,0.05,0.07)稀磁半导体材料,研究Mn~(2+)掺杂浓度对ZnS纳米棒微观结构和光学性能的影响。采用X射线衍射(XRD)、高分辨透射电子显微镜(HRTEM)、选区电子衍射(SAED)、X射线能量色散分析谱仪(XEDS)和紫外可见吸收光谱(UV-vis)对样品的晶体结构、形貌和光学性能进行表征。结果表明:制备的所有样品均具有结晶良好的纤锌矿结构,没有杂峰出现,生成纯相Zn_(1-x)Mn_xS纳米晶。样品形貌为纳米棒状结构,分散性良好。掺杂的Mn元素进入到ZnS纳米晶中,Mn~(2+)替代了Zn~(2+),而且随着Mn掺杂量的增加晶格常数减小。同时UV-vis光谱发现样品的光学带隙增大,发生了蓝移现象。     

Mn~(2+)掺杂水溶性ZnS量子点的制备及其光致发光性能

采用共沉淀法,在3-巯基丙酸(MPA)为表面修饰剂下,成功制备出Mn2+掺杂水溶性ZnS量子点。利用X射线衍射仪、透射电子显微镜、紫外-可见吸收光谱仪和荧光分光光度计等表征方法研究了Mn2+掺杂剂及掺杂量对ZnS量子点的晶体结构、形貌和发光性能等的影响。结果表明,所得产物为ZnS立方型闪锌矿结构,样品呈不规则球形,粒径主要集中在9.7nm左右;在320nm激发下,Mn2+掺杂ZnS量子点出现两个发射波峰,分别位于587和637nm处,其中587nm处的发射波峰为ZnS表面态缺陷发光,而637nm处的发射波峰则属于Mn2+∶4T1-6A1能级特征发光。同时,利用红外吸收光谱对Mn2+掺杂水溶性ZnS量子点的形成机理进行了初步探讨。     

低温水热法制备ZnS:Co+Cr纳米晶及其光学性能研究

采用低温水热法制备出3-巯基丙酸(MPA)修饰的ZnS:Co+Cr纳米晶. 利用X射线衍射仪、粒度分析仪、透射电镜、紫外-可见分光光度计、荧光分光光度计和XPS能谱仪等对ZnS:Co+Cr纳米晶的结构、形貌、粒径分布和发光性能进行了表征. 结果表明: 合成的ZnS:Co+Cr纳米晶有较好的单分散性, 平均粒径为9.3 nm, 均为立方闪锌矿结构; ZnS:Co+Cr纳米晶的吸收边位于320 nm处, 并在728 nm处出现Co²⁺的特征吸收峰; 当Cr²⁺浓度为0.75at%, 水热反应温度为160℃时, ZnS:Co+Cr纳米晶PL峰最强; XPS能谱表明Cr²⁺部分被氧化成Cr³⁺。     

基于大分子配体修饰的Cd~(2+)、Mn~(2+)掺杂功能化ZnS纳米晶的制备与表征

以醋酸锌、氯化镉、醋酸锰和硫化钠为原料,采用末端带双键的聚甲基丙烯酸(PMAA)大分子单体为配体,在水溶液中成功制备出分散均匀并具有良好荧光性的Cd2+和Mn2+掺杂复合的ZnS纳米晶.利用电导率分析、TGA、Uv-vis、荧光光谱(PL)等表征手段考察了复合纳米晶结构和光学性能的关系.结果表明,PMAA中的大量羧基是以配位键的形式和纳米晶表面金属原子相结合.通过改变掺入的Cd2+的含量,能够获得从紫外光到可见光范围的ZnS:Cd2+复合纳米晶材料.     

一种P掺杂ZnO纳米梳的制备及其光致发光性能研究

采用化学气相沉积(CVD)方法制备了P掺杂ZnO纳米梳,扫描电子显微镜(SEM)结果显示,纳米梳状产物均匀分布在Si衬底上。P掺杂ZnO纳米梳为高度结晶的六方纤锌矿结构,ZnO中P的掺杂含量约为2%(原子分数)。室温光致发光(PL)光谱表明,P掺杂ZnO纳米梳在样品不同区域的发光性能略有不同,但是均出现3个发光峰:紫外、绿光和近红外发光峰。同时PL结果也表明样品的整体结晶质量比较好。     

Ce3+、Mn2+掺杂Zn3（BO3）2的制备及其发光性能

采用共沉淀法在700℃和较短的烧结时间下制备了Zn3(BO3)2和不同浓度的Ce3+、Mn2+离子掺杂的Zn3(BO3)2纳米晶粉末,对合成产物的发光性质及发光机理进行了研究。利用荧光分光光度计、X射线粉末衍射仪以及透射电镜对其光学性能和纳米晶形貌进行了表征。结果表明Ce3+离子掺杂的Zn3(BO3)2样品在340～400nm之间有强的荧光发射,其最高发射峰峰位为365nm,在Ce3+掺量为0.5%(摩尔分数,下同)时发光强度达到最高值。Ce3+取代Zn2+离子作为发光中心,Mn2+离子作为激活剂加入,并不影响荧光发射峰的位置,但能够有效增强其发光强度。当Mn2+离子掺量为0.7%(摩尔分数)时,Ce3+、Mn2+共掺杂的Zn3(BO3)2纳米晶发光强度达到最高值。     

掺杂硫化锌的制备与光学特性的研究

采用共沉淀法制备Co~(2+)/Ni~(2+)掺杂的ZnS纳米材料,对所制备样品进行XRD、SEM和PL表征。结果表明,样品的发光峰是ZnS及掺杂离子复合作用产生的发光峰,样品分别在438nm、469nm、504nm、531nm、562nm和602nm波段表现出发光特性,并简要介绍其发光机理。     

核壳结构CdS：Mn/ZnS纳米晶的制备与光学性能研究

以3-巯基丙酸为稳定剂,采用共沉淀法在水相中合成了CdS∶Mn掺杂纳米晶,然后进一步将ZnS包覆于CdS∶Mn纳米晶表面,制备了CdS∶Mn/ZnS核壳结构纳米晶。利用X射线衍射（XRD）,透射电子显微镜（TEM）和紫外-可见吸收光谱（UV-Vis）对纳米晶的结构、形貌和光学性质进行了表征,发现制备的纳米晶具有优秀的单分散性,确认合成了CdS∶Mn/ZnS核壳结构纳米晶。通过荧光光谱（PL）研究了纳米晶的发光性质和光稳定性,结果表明包覆壳层后纳米晶的发光强度显著提高,最高可达8倍,且Mn2＋离子的发光峰峰位置随着ZnS壳层数的增加而红移。此外,核壳纳米晶的光稳定性大大提高。     

α-ZnS:Mn纳米荧光粉热分解法制备及其发光性能

以Zn(NO3)2·6H2O(硝酸锌)、Mn(NO3)2·3H2O(硝酸锰)和Ddtc·3H2O(二乙基二硫代氨基甲酸钠)为原料,制得含硫金属有机配合物。将含硫金属有机配合物在不同反应溶液中,于200℃进行热解,制备了ZnS∶Mn纳米荧光粉。结果表明,样品为六方晶系的高温相α-ZnS∶Mn。在二甘醇加5mL油酸反应溶液中制得的ZnS∶Mn纳米材料紫外吸收峰最高,粒径更小。在323nm光激发下,看到了Mn2+的橘黄色发射峰(585nm)和ZnS的蓝色发射峰(450nm),随着Mn2+离子掺杂量增加,585nm发光强度先增加后减小,掺杂量为4%时达到最大值,而450nm发光强度变化与此相反。     

Co2+掺杂水溶性ZnS量子点的制备及其光致发光性能

采用共沉淀法,以3-巯基丙酸为表面修饰剂,成功制备出Co2+掺杂水溶性ZnS量子点。采用X射线衍射仪、透射电子显微镜、原子发射光谱仪、紫外-可见吸收光谱仪和荧光分光光度计等,研究了Co2+掺杂剂及掺杂量对ZnS量子点的晶体结构、形貌和发光性能等的影响。结果表明:所得产物均为ZnS立方型闪锌矿结构,量子点呈不规则球形,粒径主要集中在5.2 nm左右;掺杂样品发红色荧光,发光性能明显增强,属于Co2+形成的杂质能级(4A1—4T1)与缺陷的复合发光。同时,利用红外吸收光谱对Co2+掺杂水溶性ZnS量子点的形成机理进行了初步探讨。     

Paramagnetic nature of Mn doped ZnS nano particles in opto electronic device application

Manganese (Mn²⁺) doped ZnS nano sized powder was prepared by co precipitation method with different concentration from 1 to 5 %. The X-ray diffraction pattern indicates that the prepared powders are in cubic structure with the crystallite sizes lie in the range of 10–12 nm. Diffuse reflectance studies enlightens that an increment in the band gap (3.38–3.55 eV) with increasing dopant. The morphology and size of the sample could be intuitively determined by field emission scanning electron microscope and it shows that ZnS and Mn doped ZnS nanoparticles are appeared as spherical shape. The replacement of Zn by Mn is confirmed by energy dispersive analysis. TEM images confirm the spherical shape of the nanoparticles and SAED images exhibit the crystalline nature and confirm the cubic nature of the synthesized samples. The prepared luminescent nanoparticles of Mn doped ZnS have emission peak at around 617 nm. The symmetry and electronic structure of the Mn doped samples are studied with electron paramagnetic resonance.The paramagnetic nature of Mn doped ZnS nano particles are validated by using vibrating sample magnetometer spectra at room temperature. Thermal analysis measurement of the samples shows that the thermal stability of Mn doped ZnS is higher than the undoped ZnS. This corroborates that ZnS:Mn doping is attributed to the removal of water and it enhanced the crystallinity.     

沉淀法制备ZnS∶Cr纳米晶及其光学性能研究

以十二烷基苯磺酸钠和六偏磷酸钠作为分散剂,采用沉淀法制备了ZnS及不同掺杂浓度的ZnS∶Cr纳米晶。利用XRD和TEM对纳米晶物相和形貌进行了分析。结果表明,ZnS和ZnS∶Cr纳米晶均为立方闪锌矿结构,利用谢乐公式估算ZnS和ZnS∶Cr纳米晶平均粒径分别为2.1和2.2nm。TEM观察到纳米晶近似为球形,平均粒度为3nm左右,具有较好的单分散性且分布均匀。荧光光谱(PL)表明,纳米晶在420、440和495nm处有发射谱带,前两者被认为是S空位深陷阱发光,后者被认为是表面态或中心辐射复合发光。     

Optical properties of Mn-doped ZnS semiconductor nanoclusters synthesized by a hydrothermal process

Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 ?. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn²⁺ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn²⁺ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn²⁺ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.     

Synthesis and characterization of ZnS:Mn2+ nano-particles for white-light emitting

The sol-gel method was used to obtain a kind of white-light emitting ZnS:Mn2+ nanoparticles capped by methacrylic acid with an average particle size of approximately 7 nm. The photoluminescence spectra, X-ray diffraction spectra, Fourier transform infrared reflection spectra and ultraviolet absorption spectra were used to measure their optical properties and crystal structures. The ZnS:Mn2+ nanoparticles with 0.58 wt% Mn2+ concentration emitted white light when excited by 380 nm. The PL spectrum exhibits two emission peaks under irradiation: one at 480 nm generated from the ZnS matrix, and one at 590 nm emitted by the doped Mn2+ ions. The nanoparticles will only emit white light with the optimum Mn2+ concentration (0.58 wt%). X-ray diffraction demonstrates the synthesized ZnS:Mn2+ nanoparticles have zinc blend crystal structure, and the infrared patterns of the capped ZnS:Mn2+ nanoparticles and methacrylic acid are comparable, indicating that the methacrylic polymer has capped or modified ZnS:Mn2+ nanoparticles.     

Synthesis and luminescence properties of ZnS:Mn/ZnS core/shell nanorod structures

Mn-doped ZnS nanorods synthesized by solvothermal method were successfully coated with ZnS shells of various thicknesses. The powder X-ray diffraction (XRD) measurements showed the ZnS:Mn nanorods were wurtzite structure with preferential orientation along c-axis. Transmission electron microscopy images (TEM) revealed that the ZnS shells formed from small particles, growing along a-axis orientation, which was proved by the XRD measurements. Room temperature photoluminescence (PL) spectra showed that the intensity of Mn emission first increased and then decreased with the thickening of the ZnS shells. The effects of ZnS shells on the luminescence properties of ZnS:Mn nanorods is discussed.     

Photoluminescence decay kinetics of doped ZnS nanophosphors

Doped nanophosphor samples of ZnS:Mn, ZnS:Mn, Co and ZnS:Mn, Fe were prepared using a chemical precipitation method. Photoluminescence (PL) spectra were obtained and lifetime studies of the nanophosphors were carried out at room temperature. To the best of our knowledge, there are very few reports on the photoluminescence investigations of Co-doped or Fe-doped ZnS:Mn nanoparticles in the literature. Furthermore, there is no report on luminescence lifetime shortening of ZnS:Mn nanoparticles doped with Co or Fe impurity. Experimental results showed that there is considerable change in the photoluminescence spectra of ZnS:Mn nanoparticles doped with X (X = Co, Fe). The PL spectra of the ZnS:Mn, Co nanoparticle sample show three peaks at 410, 432 and 594?nm, while in the case of the ZnS:Mn, Fe nanoparticle sample the peaks are considerably different. The lifetimes are found to be in microsecond time domain for 594?nm emission, while nanosecond order lifetimes are obtained for 432 and 411?nm emission in ZnS:Mn, X nanophosphor samples. These lifetimes suggest a new additional decay channel of the carrier in the host material.     

Time resolved spectroscopic studies on some nanophosphors

Time resolved spectroscopy is an important tool for studying photophysical processes in phosphors. Present work investigates the steady state and time resolved photoluminescence (PL) spectroscopic characteristics of ZnS, ZnO and (Zn, Mg)O nanophosphors both in powder as well as thin film form. Photoluminescence (PL) of ZnS nanophosphors typically exhibit a purple/blue emission peak termed as self activated (SA) luminescence and emission at different wavelengths arising due to dopant impurities e.g. green emission for ZnS: Cu, orange emission for ZnS: Mn and red emission for ZnS: Eu. The lifetimes obtained from decay curves range from ns to ms level and suggest the radiative recombination path involving donor-acceptor pair recombination or internal electronic transitions of the impurity atom. A series of ZnMgO nanophosphor thin films with varied Zn: Mg ratios were prepared by chemical bath deposition. Photoluminescence (PL) excitation and emission spectra exhibit variations with changing Mg ratio. Luminescence lifetime as short as 10⁻¹⁰ s was observed for ZnO and ZnMgO (100: 10) nanophosphors. With increasing Mg ratio, PL decay shifts into microsecond range. ZnO and ZnMgO alloys up to 50% Mg were prepared as powder by solid state mixing and sintering at high temperature in reducing atmosphere. Time resolved decay of PL indicated lifetime in the microsecond time scale. The novelty of the work lies in clear experimental evidence of dopants (Cu, Mn, Eu and Mg) in the decay process and luminescence life times in II–VI semiconductor nanocrystals of ZnS and ZnO. For ZnS, blue self activated luminescence decays faster than Cu and Mn related emission. For undoped ZnO nanocrystals, PL decay is in the nanosecond range whereas with Mg doping the decay becomes much slower in the microsecond range.     

Synthesis and optoelectrochemical properties of ZnS:Mn nanocrystals

Mn2+ ions doped ZnS semiconductor nanocrystals (ZnS:Mn NCs) were synthesized using colloidal chemical method at 70 degrees C without any capping agents. The as-prepared undoped ZnS and ZnS:Mn NCs were characterized by UV-Vis absorption spectra, fluorescent emission spectra, X-ray powder diffraction (XRD), inductively coupled plasma analysis (ICP), X-ray photoelectron spectroscopy (XPS), Dynamic light scattering (DLS), cyclic voltammogram and electronic transmission microscopy (TEM). The dependence of photoluminescence of ZnS:Mn NCs on dopant concentration was studied. The results show that Mn2+ ions mainly stay at ZnS nanocystal surface, and Mn2+-surface defect state complex was formed, as a result of which, surface defect emission of ZnS nanocrystals was substituted with Mn2+-related PL emission. The strongest fluorescent emission intensity was obtain at 1.85 at% Mn2+ doped ZnS:Mn NCs. The Mn2+ doped ZnS:Mn NCs are of 5 nm in diameter. The emission peak at 575 nm is attributed to d-d (4T1 --> 6A1) transition of Mn2+ ions. The existence of Mn2+-related photoluminescence could be well correlated with cyclic voltammogram of Mn2+-doped NCs, where pair of oxidation and reduction peaks were clearly observed due to the doped Mn2+ ions. The adsorbed Mn2+ ions on ZnS NCs produced neither Mn2+ emission nor redox peaks. For heavily doped ZnS:Mn NCs (4.87 at%), redox peaks gap in cyclic voltammogram became larger and new oxidation peak appeared. Correspondingly, when the Mn2+ doping concentration reached 4.87 at%, the Mn2+-related emission totally disappears due to the Mn-Mn interactions. This work implys that electrochemical technique is possibly an useful tool to probe the local structure of doped Mn2+ ions.     

Luminescent properties of ZnS:Mn2+/ZnS core/shell nanocrystals

High-quality ZnS:Mn2+/ZnS core/shell nanocrystals (NCs) with a core crystal diameter of 6.1 nm and 1.15 nm thick shells were synthesized via a high-boiling solvent process. The energy levels of the conduction band and valance band are estimated to be -3.2 eV and -6.8 eV by cyclic voltammetry and ultraviolet-visible (UV-vis) absorption spectra. The ZnS:Mn2+/ZnS NC emission peak is primarily located at 580 nm under 310 nm light excitation, originating from the charge transition from 4T1 to 6A1 within the 3d5 configuration of the Mn2+ ion. Based on ZnS:Mn2+/ZnS NCs as the active layer electroluminescent devices, the emission peak mainly locates at 460 nm with one shoulder emission peaking at 580 nm. The photoluminescence and electroluminescence properties of ZnS:Mn2+/ZnS NCs are investigated in the view of charge carrier injection and energy level alignment.