Ultrasonication solid state chemical reaction synthesis and characterization of nanocrystalline Zn(Oxin)2?2H2O (zinc 8-quinolinolate)
LI Dao-hua(李道华)
Department of Chemistry and Life Science, Neijiang Teachers College, Neijiang 641112, China
Received 10 April 2006; accepted 25 April 2006
Abstract: Under near ambient temperature and ultrasonication, nanocrystalline Zn(Oxin)2?2H2O (zinc 8-quinolinolate) was synthesized by solid state chemical reaction. The particle size distribution was relatively uniform, the morphology of the mare was ball like particle. The phase, particle size and morphology of the prepared nanocrystalline were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron diffraction (ED). The results show that the crystallite product has an average size of about 30 nm. The effects of a series of reaction conditions on the synthesis of Zn(Oxin)2?2H2O by solid state reaction were studied. During the synthesis of nanocrystalline Zn(Oxin)2?2H2O, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different times may influence morphology, particle size and the size distribution of final products.
Key words: zinc 8-quinolinolate; nanocrystallite; ultrasonication; solid state chemical reaction
1 Introduction
With the deep development of nanocrystalline research, it becomes very important to present special demands for physical, chemical characters, preparing high pure super-fine, even-nanocrystalline, and produce new nanocrystalline materials. And the key is to study and develop new synthesis technique. Usually, the preparation of nanocrystalline needs: clean-surface; the shape of particle, the particle size and the granularity being controllable; nanocrystalline not becoming together; easily collecting; good stability and high productivity. The study on the solid state chemical reaction under room temperature and near room temperature has got great progress. Using solid state chemical reaction nanocrystalline materials is a new method which is developed recently. Its advantages are operating conveniently, easily controlled granularity and less pollution. It also could avoid or reduce the phenomenon of hard gathering and particle gathering caused by middle step and high temperature reaction. Solid state chemical reaction process goes through four steps: spread, reaction, forming nuclear and growth. When the speed of forming nuclear is bigger than nuclear growing speed, it is beneficial to growing nanocrystalline particle. But if nuclear growing speed is bigger than speed of forming nuclear, the lump crystal will be formed. Nanocrystalline material has small size effect, quantum volume effect, surface effect, and macroscopic quantum tunnel effect. It shows super property in chemicals, catalyst, optics electricity, voice, superdome activity, living things activity and so on. It also has a very high practical value in nation defense, chemical industry, nuclear technology, metallurgy, astronavigation, light, living things, medicine and so on. Recently it has become a good foundation for developing special function materials and has been an active field of physical, chemical and material science research [1-3].
Zn(Oxin)2?2H2O is an important chelate fluore- scence material and has good characters of shining. The shining color is yellow. It has the characteristics of high efficiency of fluorescence, good property of becoming membrane, easy purification, high melting point and a stable property. Zn(Oxin)2?2H2O, as a new organic fluorescent material, has been researched, but there is no report about composing nanocrystallite Zn(Oxin)2?2H2O. Microsizing can improve the membranization and heat stability of material and elongate material’s lifespan. In this paper, we used solid state chemical reaction in the process of composing nanocrystallite material at the near ambient temperature and by the motivation of ultrasonic, used the synthesized Zn(Oxin)2?2H2O nanocrystallite material made out of the solid state chemical reaction, and then the phases, particle size and morphology of the prepared nanocrystallite were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) and electron diffraction (ED). The different ways in the solid state chemical reaction were reported, such as changing reactant, reactant’s rate, joining the inertial material, adding scruple solvent or surface alive material, changing the time of grinding, to affect composing nanocrystallite. The perfect technology condition and means to make nanocrystalite material were also discussed [4-9].
2 Experimental
The experiment reagents were all the analytical purity. Baking 5.0 mmol ZnSO4?7H2O and 10.0 mmol Oxine(8-quinolinolate) to grind in the agate pot with infrared light during grinding, the temperature was 35-40 ℃, with the operation of ultrasonic, to wash the lomposing three times with distilled water, and then wash two times with alcohol, drying, finally the Zn(Oxin)2?2H2O nanocrystlline.
To prepare Zn(Oxin)2?2H2O nanorystallite with ZnCl2, Zn(OH)2, Zn(Ac)2?2H2O separately as reaction instead of ZnSO4?7H2O. The process was as the same as before. Grinding the mixture of 2.5 mmol Zn(Ac)2?2H2O and 5.0 mmol Oxine and 5.0 mmol NaOH, made it mix and grinded with 5.0 mmol Oxine for 30 min, or put 5.0 mmol Oxine and 5.0 mmol NaOH together and after it became yellow, made it together with fine 2.5 mmol Zn(Ac)2?2H2O, then went on grinding for 30 min, to prepare Zn(Oxin)2?2H2O nanocrystallite, as the same as the way we did before.
Analysed the object state with powder X-ray diffraction (XRD) and electron diffraction, observed the shape and size of particle with transmission electron microscopy (TEM). The XRD pattern choosed Cu on Rigaku D/Max-RA type of X-ray powder diffraction machine by Be-window color filter machine and plumbago single-color machine, the speed of scanning was 40??min-1; the region of scanning was 5?≤2θ≤60?, tube voltage 40 kV; tube current 50 mA. Every time we used the machines whose constant and power were the same. The TEM and electric diffraction pictures were tested by Japanese electronic type of JEM-200 CX transmission electric microscope, accelerated voltage was 160 kV, was amplified 100 thousand times.
3 Results and discussion
Reactant Zn(Ac)2?2H2O was mixed with Oxine together and evened up. According to grinding under the circumstance of heating by infrared light, it can produce yellow powder thing immediately. That is to say it can have solid state chemical reaction and react quickly.
Fig.1 shows the XRD patterns of Zn(Oxin)2?2H2O nanocrystallite (synthesized according to No.18 in Table 1) which is according closed room temperature ultrasonic wave solid chemical reaction. The result shows that, after grinding and reaction, with the ultrasonic wave affection, the XRD pattern of the produced Zn(Oxin)2?2H2O getting rid of liquidized objects with and without water is almost the some with the XRD pattern of pure Zn(Oxin)2?2H2O and standard Zn(Oxin)2?2H2O diffra- ction, X-ray powder diffraction PDF card, and have no impurity peak. But the product of solid state chemical reaction’s feature diffraction is weaker conspicuous. According to X-ray polycrystal diffraction theory, the particle size in the peak diffraction is widen because of the shortening of the product. This shows the speed of the particle solid state producer Zn(Oxin)2?2H2O is super tiny pellet. According to the diffraction of the XRD pattern wide of Simi peak, we can get the crystal’s average size of particle 32 nm with the formula of Scherrer. Because the size of reactant particle is decided by crystal nucleus’s growing speed and speed is becoming fast. The reaction has quick speed at room temperature, the speed of becoming nuclear is quicker than that of the nucleus. So we can get the smaller nanocrystallite.
Fig.1 XRD patterns of nanocrystalline Zn(Oxin)2?2H2O: (a) Nanocrystalline Zn(Oxin)2?2H2O; (b) Pure Zn(Oxin)2? 2H2O
Fig.2 shows the electron diffraction pattern of this sample (Synthesized according to No.18 in Table 1). The result shows that the round line of the diffraction is clear and tied with the result of multicrystal diffraction. This also shows that it is the multicrystal Zn(Oxin)2?2H2O.
Fig.2 Electron diffraction (ED) pattern of nanocrystalline Zn(Oxin)2·2H2O
Fig.3 shows the observation result of transmission electron (TEM) of the sample, the shape of the nanocrystallite Zn(Oxin)2·2H2O like a ball, most of the nanocrystallite’s size is about 30 nm, it is nearly the same with the X-ray diffraction result.
Fig.3 TEM image of nanocrystalline Zn(Oxin)2?2H2O (synthesized according to No.18 in Table 1)
Using ZnCl2, Zn(OH)2, Zn(Ac)2?2H2O, Zn(Ac)2? 2H2O+ NaOH instead of ZnSO4?7H2O as the reaction is through solid state reaction to compose the nano- crystalline Zn(Oxin)2?2H2O (synthesized according to No.1 to 5 in Table 1), the pattern of X-ray diffraction (XRD), the figure of transmission electron microscope (TEM) and the electron diffraction pattern are all like Zn(Oxin)2?2H2O, which composed by the using of ZnSO4.7H2O as the reactant, after enough reaction, its all can make out single nanocrystalline, the result of the X-ray diffraction (Table 2). But it can be seen from the TEM photograph that the sizes for nanocrystalline Zn(Oxin)2?2H2O of different reactants are even and the order of granular sizes is Zn(Ac)2?2H2O＜Zn(Ac)2? 2H2O+NaOH＜Zn(OH)2＜ZnCl2?2H2O＜ZnSO4?7H2O (Table 1), among which the nanocrystalline particle of Zn(Ac)2?2H2O is the smallest. It can be seen from the color change of reactants in the mixing and grinding reactions that their reaction speeds are different. Using Zn(Ac) 2?2H2O as reactant, the reaction speed is the fastest, and because the faster the reaction speed is, the faster the forming speed of nucleus is, and the growing speed of nucleus remains the same, the granular size of the product is smaller. Thus in production and preparation experiments on other conditions, Zn(Ac)2? 2H2O and Oxine are used as main reactants.
The XRD pattern of nanocrystalline Zn(Oxin)2? 2H2O synthesized according to different matching proportion of reactant (synthesized according to No.6 to 8 in Table 1) are similar. It can be seen from the TEM photograph that with the increase of proportion for anion of reactant, the granularity of particles is reduced and its dispersion is better than before because the increase of reactant density might hasten the forming speed of nucleus so as to decrease the granularity of product particles.
Adding inert substances like NaCl and NaAc can make the product particles smaller, and the result of adding NaCl is slightly better. After adding NaAc on the basis of different matching proportion (synthesized according to No.9 to 15 in Table 1), powder X-ray diffraction (XRD) of the products shows that the XRD pattern of Zn(Oxin)2.2H2O are similar to the standard XRD pattern of Zn(Oxin)2?2H2O, and the product belongs to nanocrystalline. It can be seen from the TEM photograph that the particle of Zn(Oxin)2?2H2O is in the shape of diamond. Moreover, while the matching proportion of NaAc becomes large, the produced particles of Zn(Oxin)2?2H2O gradually become small, and when the matching proportion reaches 16:1, the size of the particle diameter is about 50 nm.
In solid state chemical reaction those substances that didn’t take part in the reaction all belonged to insert substances, and appropriate amount of insert substance, which was easily got away with, could be added in order to change the forming and growing speed of product nucleus. On one hand, the added insert could make the reactant more dispersive and mix more evenly, and make the growing speed of the product particle slow down and the produced particle become small. On the other hand, by adding insert, the reaction speed of the system and the forming speed of nucleus would slow down. Therefore, the matching proportion should be appropriately controlled so as to achieve the best result.
The XRD pattern of Zn(Oxin)2?2H2O synthesized by adding all kinds of solvents or surface active solvents (synthesized according to No.16 to 22 in Table 1) were similar as well, and all the products were one phase
Table 1 Morphology and particle size of nanocrystalline Zn(Oxin)2?2H2O under different conditions by solid state reaction
Table 2 X-ray diffraction result of nanocrystalline Zn(Oxin)2?2H2O
nanocrystalline Zn(Oxin)2·2H2O. It can be seen from the TEM photograph that by adding tiny amount of solvent or surface active solvent the product particles become slightly small and the particle diameters disperse evenly. Solvents or surface active solvents could promote the reactants in solid state chemical reaction system to contact and disperse, and quicken the reaction speed. By adding phenthiol the best result could be achieved. Fig.4 shows the TEM photograph of the nanocrystalline Zn(Oxin)2?2H2O examples (synthesized according to No.20 in Table 1) and it shows that the produced nanocrystalline Zn(Oxin)2?2H2O are irregular particles, most of which are about 40 nm in size.
Fig.4 TEM photograph of nanocrystalline Zn(Oxin)2?2H2O (synthesized according to No.20 in Table 1)
Fig.5 TEM photograph of nanocrystalline Zn(Oxin)2?2H2O (synthesized according to No.19 in Table 1)
Even by grinding the reactant at different times, the XRD pattern of Zn(Oxin)2?2H2O are similar. The size difference between the nanocrystalline Zn(Oxin)2?2H2O particles is not obvious after grinding the reactant for 20 min and 30 min, but after grinding the reactant for 60 min the nanocrystalline particle obviously becomes large (The examples were synthesized according to No.17, 18, and 19 in Table 1). Because ground after 30 min, the reactant reacted basically completely and if the grinding continued, growth of the nanocrystalline nucleus occupied the main process and the diameter of the nanocrystalline particle became large. Fig.5 shows the TEM photograph of the nanocrystalline Zn(Oxin)2?2H2O examples (synthesized according to No.19 in Table 1) and it shows that the produced nanocrystalline Zn(Oxin)2?2H2O are nearly ball like, most of which are about 60 nm in size.
4 Conclusions
Under near ambient temperature and ultrasonication, nanocrystalline Zn(Oxin)2?2H2O was synthesized by solid state chemical reaction. The particle sizes are relatively uniform, the morphology of the mare is ball like, and the average particle diameter is about 30 nm. The best technological condition for nanocrystalline Zn(Oxin)2?2H2O in solid state reaction synthesis is: using Zn(Ac)2?2H2O and Oxine (1:4) as reactant, after adding appropriate amount of inert substance NaAc (The proportion is 8:1 of inert substance and amount of substance for Zn ) and mixing evenly, joining appropriate amount of solvent or surface active solvent phenthiol (1 mL) and grinding 30 min under the condition of heating by red light, then, under the action of ultrasound, cleaning mixture fully with distilled water and cleaning it withalcohol again, dry it naturally, finally, the productive rate of nanocrystalline Zn(Oxin)2?2H2O is 96.8%.
In conclusion, during the synthesis of nanocrystalline Zn(Oxin)2?2H2O, the solid state reaction conditions such as changing reactant, matching proportion of reactant, adding inert substance, joining a little solvent or surface active solvent and grinding at different time may influence morphology, particle size and the size distribution of final products.
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(Edited by LI Xiang-qun)
Foundation item: Project (29631040) supported by the National Natural Science Foundation of China; Project (200604) supported by the Scientific Research Foundation of Neijiang Teachers College, China
Corresponding author: LI Dao-hua; Tel: +86-832-2342433; E-mail: daohl@163.com
