An influence of the kinetic parameters of the reaction on a size of obtained nanoparticles at the reduction of silver ions by hydrazine Текст научной статьи по специальности «Нанотехнологии»

УДК 537.5282 ББК 28.0

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AN INFLUENCE OF THE KINETIC PARAMETERS OF THE REACTION ON A SIZE OF OBTAINED NANOPARTICLES AT THE REDUCTION OF SILVER IONS BY HYDRAZINE

Kytsya Andriy Romanovych

Associate professor of chemical science, Senior researcher

Department of Physical Chemistry of Fossil Fuels InPOCC, National Academy of Sciences of Ukraine

andriy_kytsya@yahoo. com

R. Liuksemburg St., 70, 83114 Donetsk, Ukraine

Hrynda Yuriy Mykolayovych

Junior researcher of Department of Physical Chemistry of Fossil Fuels InPOCC

National Academy of Sciences of Ukraine

chimikur4uk@gmail. com

R. Liuksemburg St., 70, 83114 Donetsk, Ukraine

Bazylyak Liliya Igorevna

Associate professor of chemical sciences, Senior researcher of Department of Physical Chemistry of Fossil Fuels InPOCC National Academy of Sciences of Ukraine [email protected] R. Liuksemburg St., 70, 83114 Donetsk, Ukraine

Zaikov Gennady Efremovich

Doctor of chemical sciences, Professor, Head of Division of biological and chemical physics of Polymer The Federal State Budget Institution of Science N. M. Emanuel Institute of Biochemical Physics

w Ö

g [email protected]

rj| Kosygin st., 4, Moscow 119334, Russian Federation

i-^ Abstract. Kinetics of the reaction of silver nitrate reduction by hydrazine in the presence

^ of sodium citrate in alkaline medium was studied in a wide range of the reagents concentration variation. The orders of the reaction were determined and the effective constants of the silver is nanoparticles nucleation process rate and of their propagation one were calculated. It was ^ investigated the optical characteristics of the obtained sols of the silver nanoparticles. It was ^ determined the empirical dependence of a size of the obtained silver nanoparticles on the

^ kinetic parameters of a process.

CÖ

ö Key words: silver nanoparticles, nucleation, nanoparticles growth, kinetics, hydrazine.

£

<C 1. Introduction a synthesis of the nanoparticles of noble metals,

^ studies of their properties and practical application

^ An exponential growth in a field of the is observed for the last decades. Silver

© fundamental and applied sciences connected with nanoparticles (Ag-NPs) are characterized by

unique combination of the important physical-chemical properties, namely by excellent optical characteristics caused by the phenomena of the surface plasmon resonance [5], by ability to amplify the signal in spectroscopy of the combination dispersion and also by high antibacterial properties. Despite the fact, that there are a number of methods for the synthesis of different upon nature nanoparticles and nanomaterials describing in references [3; 4; 10; 11; 14; 15], however the kinetic peculiarities and regularities of the formation (nucleation and propagation) of nanoparticles studied insufficiently and has the episodical character [2; 6; 6].

That is why the aim of the presented work was to investigate an influence of the synthesis conditions on the kinetic parameters of a process and also on the form and on the size of the synthesized Ag-NPs.

2. Experimental Section

Ag-NPs were obtained in accordance with the reaction (1) via reduction of silver nitrate by hydrazine in aqueous medium in the presence of sodium hydroxide at 20 0C:

4 AgNO3 + 4 NaOH + N2H4 = = 4 Ag + 4 NaNO3 + 4 H2O + N2- (1)

Sodium citrate has been used as the stabilizer at its concentration 1x10-4 mole/l in the reactive solution.

Kinetic of the reaction was studied by direct potentiometry method with the use of the ion-selective microelectrode «ELIS-131 Silver». The concentration of the silver ions was determined continuously during the reaction proceeding per change of the potential of the ion-selective electrode regarding to the chlorine-silver comparison electrode. In order to avoid the hit of the chlorine ions into the reactive mix the salt weak link with the potassium nitrate was used.

The form and the average diameter of the silver nanoparticles were estimated with the use of the scanning electron microscopy EV0-40XVP (Carl Zeiss) with a system of the X-ray microanalysis INCA Energy, XRD-analysis and also on a basis of the adsorption spectra of the surface plasmon resonance of Ag-NPs sols with the use of the single-beam spectrophotometer UV-visible

range UVmini-1240 (P/N 206-89175-92; P/N 206-89175-38; Shimadzu Corp., Kyoto, Japan).

XRD-analysis was carried out with the use of XRD diffractometer DR0N-3.0 with Cu-Ka irradiation (l = 1,5405 nm). Data have been analyzed by full-profile revision in accordance with the Ritveld's method with the use of the simulation package GSAS (General Structure Analysis System).

3. Results and Discussion

In order to explain and to investigate the chemical process of the silver nanoparticles synthesis the kinetic characteristics have been investigated, namely the change of the concentration of the silver ions during the experiment. Typical kinetic curves of the silver concentration change via time are represented on Fig. 1.

As we can see, the starting section of the kinetic curve corresponds to the stage of the nucleus centers formation and the following sharp decrease of the concentration of silver ions corresponds to their growth stage. Therefore, the time (t0) of the initial section of the kinetic curve determines the Ag-NPs nucleation rate (W0 = 1/t0), and the tangent of the angle of inclination of its quick linear section determines the rate of the nucleus growth (Wmax).

It was investigated an influence of the change of starting concentrations of silver nitrate, sodium hydroxide and hydrazine on kinetic parameters of a process. In order to increase the trustworthiness of the results, the series of investigations consisting of 7-10 experiments has been carried out for every concentration. Obtained data were averaged. The ratio error at the Wn and determination not exceeds 25 %.

0 ^max

Taking into account, that the reagents change concentration at the nucleation stage and also at the stage of the starting section of the silver NPs growth is insignificant, it can be used with some approximation the dependencies of the rates of a process on the starting concentrations of reactive mix components in order to determine the orders of the reaction.

Presented on Fig. 2 data indicate that the orders of the reaction per every among reagents for the processes of silver nanoparticles nucleation and growth are agreed and are equal to 1, 1 and 1/2 for AgNO3, NaOH and N2H4 correspondingly.

Taking into account the determined orders of the reactions per every components, obtained experimental results can be represented in the coordinates of the acting masses law (2):

W = k# [Ag+]1 x [OH ]1 x [N2H4]1/2

(2)

and the numerical values of the effective constants rates of the processes of new phase nucleation (kf# = (2,2±0,2)x108 (mole/l)-2'5xs-1) and its

growing (kg# = (1,8±0,4)x105 (mole/l)-2xs-1) can be estimated (fig. 3).

In order to identify the obtained silver nanoparticles, their spectral characteristics were investigated (Fig. 4 a). The all spectra of silver nanoparticles adsorption are characterized by one maximum corresponding to their spherical form [5]. Analyzing the references, it was discovered that the value of the square of wave frequency in adsorption maximum of the surface plasmon

Fig. 1. Kinetic curves of the reduction reaction of silver ions by hydrazine at different starting concentrations of

the silver nitrate

1,0x10'" 1,5x10'* 2,0x10"4 2,5x1g"4 3,0x10'"

[Ag\, mole/I

a)

6,0x10 8,0x10 1,0x10 1,2x10 1,4x10 1,6x10 1,8x10

[OH"]0, mole/l

b)

4,0x10 »

jD о

„„ „„-. E

4.0x10 5,0x10 6,0x10

[N H I1'2, (mole/1)1'2

c)

Fig. 2. Dependencies of the silver nanoparticles nucleation rate W0 (•) and of the growth rate Wmax (o) on the initial concentrations ofAgNO3 (a), NaOH (b) and N2H4 (c).

resonance of silver nanoparticles linearly depends on their size (Fig. 4, b), that gives the possibilities to calculate an average diameter of the obtained silver nanoparticles. Calculated values of the average diameter of silver nanoparticles consist of 13-35 nm depending on the synthesis conditions.

Silver nanoparticles obtained at 20 0C and starting concentrations of reagents [AgNO3]0 = 2,5 x 10-4 M, [NaOH]0 = 3,0 x 10-4 M, [N2H4]0 = 7,5 x 10-5 M were investigated with the use of the SEM and XRD analysis methods for confirmation of the obtained calculations (Fig. 5). On a basis of the XRD-analysis results, an average size of the silver crystallites was calculated; it consists of DV = 9,3 nm; respectively the diameter of the spherical particle for monodisperse system is D = 4/3 and DV = 12,4 nm. Calculated accordingly to the location of the surface plasmon resonance adsorption maximum of the sol silver nanoparticles (Fig. 4 b) value of average diameter of silver nanoparticles obtained under such conditions consists of 13 nm.

At the analysis of the experimental data it was found that the size of the obtained silver nanoparticles depends on the ratio of the nuclear centers formation rate and the nuclear centers growth rate (Fig. 6).

Such dependence can be explained by fact that at the nuclear centers formation rate increasing not only the concentration of the nuclear centers is increased, but also their critical radius is decreased that leads to the decreasing of the average size of synthesized nanoparticles. Evidently, such dependence is the partial case and is determined by the conditions of the synthesis and by the choice of the reagents, however permits to obtain the silver nanoparticles by the controlled size.

4. Conclusions

The reaction of the silver ions reduction by hydrazine has been investigated in alkaline medium in the presence of the sodium citrate. It was

Fig. 3. Dependencies of W0 (•) and Wmax (o) on composition of the initial concentrations of the reagents in

coordinates of the equation (2).

со , sec

к, ПМ

3x10 -

2x10'

a) b)

Fig. 4. Adsorption electron spectra of silver nanoparticles obtained at different starting concentrations of sodium hydroxide (a) and calibration plot for calculation of their average diameter (b) based on the references [6-7; 11-15]

Ь)

Fig. 5. SEM image (а) and XRD-spectrum (b) of silver nanoparticles obtained at the starting concentrations [AgNOJ = 2,5 x 10-4 mole/1, [NaOH]n = 3,0 x 10-4 mole/1, [НД ]„ = 7,5 x 105 mole/1.

40-

d, пм

30-

■ [AgNO3]0

о [NaOH]0

▲ [N.HJo

20-

10- d = 10 + 33exp{-2500(Wmax/Wo)}

0,0

4,0x10

8,0x10 1,2x10

W /W„

Fig. 6. Dependence of an average diameter of silver nanoparticles on kinetic parameters of the process: an average diameter of silver nanoparticles obtained at different starting concentrations of AgNO3 (?), NaOH (o)

and N2H4 (A).

determined that the rates of the nucleation and of the growth of silver nanoparticles linearly depend on the initial concentrations of silver nitrate, sodium hydroxide and on concentration of hydrazine in degree 1/2. It was discovered the empirical dependence of a size of obtaining nanoparticles on the ratio of the rates of growth and nucleation of silver nanoparticles.

Acknowledgment

This work was performed via the framework of the Task Complex Program TCPSI «RESURS» (grant # Р 8.2-2013/K).

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ВЛИЯНИЕ КИНЕТИЧЕСКИХ ПАРАМЕТРОВ РЕАКЦИИ НА РАЗМЕР ПОЛУЧАЕМЫХ НАНОЧАСТИЦ ПРИ ВОССТАНОВЛЕНИИ СЕРЕБРЯНЫХ ИОНОВ ГИДРАЗИНОМ

Киця Андрей Романович

Кандидат химических наук, старший научный сотрудник отделения физико-химии горючих ископаемых

Института физико-органической химии и углехимии им. Л.М. Литвиненко НАН Украины

andriy_kytsya@yahoo. com

ул. Р. Люксембург, 70, 83114 г. Донецк, Украина

Грында Юрий Миколаевич

Младший научный сотрудник отделения физико-химии горючих ископаемых Института физико-органической химии и углехимии им. Л.М. Литвиненко НАН Украины chimikur4uk@gmail. com

ул. Р. Люксембург, 70, 83114 г. Донецк, Украина

Базыляк Лилия Игоревна

Кандидат химических наук, старший научный сотрудник отделения физико-химии горючих ископаемых

Института физико-органической химии и углехимии им. Л.М. Литвиненко НАН Украины [email protected]

ул. Р. Люксембург, 70, 83114 г. Донецк, Украина

Заиков Геннадий Ефремович

Доктор химических наук, профессор,

заведующий отделом биологической и химической физики полимеров Федерального государственного бюджетного учреждения науки Институт биохимической физики им. Н.М. Эмануэля РАН chembio@sky. chph. ras.ru

ул. Косыгина, 4, 119334 г. Москва, Российская Федерация

Аннотация. Была изучена кинетика реакции восстановления нитрата серебра гидразином в широком диапазоне изменения концентрации реактивов. Были определены параметры реакции и эффективные константы скорости процесса образования ядра наночастиц серебра и их распространения. Были исследованы оптические особенности полученных солей наночастиц серебра. Была определена эмпирическая зависимость размера полученных серебряных наночастиц от кинетических параметров процесса.

Ключевые слова: серебряные наночастицы, образование ядра, рост наночастиц, кинетика, гидразин.