Size Adjustment of Iron Phosphate Nanoparticles by Using Mixed

Article pubs.acs.org/IECR

Size Adjustment of Iron Phosphate Nanoparticles by Using Mixed Acids Tongbao Zhang, Yangcheng Lu,* and Guangsheng Luo State Key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, 10084, Beijing ABSTRACT: In this work, the size adjustment of FePO4 nanoparticles in the range of 9−50 nm was conducted on a general platform of coupling fast precipitation in a microreactor and thermal treatment process. Specifically, we used the mixture of nitric acid and phosphoric acid as the continuous fluid to change the free Fe3+ concentration and control the supersaturation of FePO4 in fast precipitation. Inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD) verified that as-prepared nanoparticles were high-purity amorphous FePO4·2H2O. Transmission electron microscopy (TEM) verified their good dispersity and narrow size-distribution (standard deviation, ∼5 nm). Brunauer−Emmet−Teller (BET) and Cr (III) adsorption verified their property accordant as ion adsorbents. The effect of mixed acids on species with respect to iron was also investigated by UV−vis spectra. The technique would be easily scaled up for size controllable and property accordant FePO4 nanoparticles preparation.

1. INTRODUCTION The preparation of nanoparticles with controllable size and good dispersion has drawn consistent attention in the nanomaterial and nanotechnology area, which has significant importance for fundamental researches1−3 as well as critical relevance for numerous size-dependent practical applications like energy conversion and storage,4 catalysis,5 adsorption,6 chemical and biological sensing,7,8 drug delivery,9 optical and spectroscopic response,10 biotagging and bioimaging,11 etc. For the past few years, iron phosphate nanoparticles have gained considerable research interest in virtue of abundant sources, environmental compatibility, and remarkable performance in the fields of lithium battery,12−14 catalysis,15−17 adsorption,18,19 ferroelectrics,20 and glass and steel industries.21 Iron phosphate nanoparticles have also been proposed as an alternative for iron (Fe) nutritional supplementation and/or food fortification recently.22 The application of iron phosphate is highly size dependent. For example, the small particle size of iron phosphate is crucial for assuring high electrochemical performance of a lithium battery.23−25 When used as a catalyst for selective oxidative dehydrogenation of lactic acid to pyruvic acid, nanosized iron phosphate particles possess much better catalytic activity than bulk ones.26 Moreover, smaller iron phosphate particles are verified to achieve higher bioavailability and lower subchronic toxicity by experiments in rats.22 Many efforts have been devoted to the preparation of iron phosphate nanoparticles. By now, well established synthetic methods include template-free precipitation in a microreactor,27 flame spray pyrolysis,22 microwave-assisted method,28 phase-transfer strategy,29 and other kinds of surfactant-assisted techniques,30,31 etc. However, researches on the size adjustment of iron phosphate nanoparticles are really limited. To our best knowledge, Yi et al. reported the manipulation of iron phosphate nanoparticles size in the range of 50−150 nm,28 and other regions remain unclear. Synthesis of nanoparticles with controllable size requires a detailed understanding of the process mechanism and controllable reaction conditions. For iron phosphate preparation, the © XXXX American Chemical Society

reaction mechanism is dependent on the starting concentration of iron and phosphate ions and pH.32 In our previous work,27 a new and facile method by coupling fast precipitation in a membrane microreactor and thermal treatment for iron phosphate nanoparticles preparation was successfully developed, and the process mechanism has been carefully explored. The size of the primary particles generated in the membrane microreactor was confirmed to determine the size of final product mostly. Since the membrane microreactor had superior and reproducible mixing performance, the size of the primary particle was almost dependent on the degree of supersaturation of iron phosphate and iron hydrogen phosphate directly, in which the concentration of Fe3+ is a critical factor. In our previous experiments, phosphoric acid was added to Fe(NO3)3 solution as the continuous feed to suppress the hydrolysis of Fe3+. Consequently, the actual concentration of Fe3+ was lower than the theoretical value for the coordination effect of Fe3+ with [HnPO4]−(3‑n) (n = 0, 1, 2). The strategy for adjusting the size of iron phosphate nanoparticles naturally occurs to us by using non/weak coordination acids as a substitute for phosphate acid. Therefore, we focused on the size adjustment of iron phosphate nanoparticles in the range below 50 nm by using nitric acid to substitute phosphoric acid partially or totally as an inhibitor for Fe3+ hydrolysis. The changing of the existing state of iron in feedstock was checked by UV−vis measurements. Transmission electron microscopy (TEM), X-ray powder diffraction (XRD), inductively coupled plasma−optical emission spectroscopy (ICP-OES), and Brunauer−Emmet−Teller (BET) analyses were employed to characterize the purity, dispersity, and size distribution of iron phosphate products. Cr(III) adsorption experiments were carried out to investigate Received: January 17, 2013 Revised: April 25, 2013 Accepted: May 9, 2013

A

dx.doi.org/10.1021/ie400192y | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

Article

hydrochloric acid solution. The power of the plasma was 1150 W. Peristaltic pump rotation speed was 100 r/min. The specific surface area, pore size distribution, and pore volume of the product were measured at −196 °C (77 K) by BET (Quantachrome Autosorb-1-C). Prior to analysis, the samples were outgassed under vacuum at 180 °C overnight. The pore size distribution was calculated from the desorption branches using the Barrett−Joyner−Halenda (BJH) method. Cr(III) concentration in aqueous solution was determined by a Polarized Zeeman atomic absorption spectrophotometer (AAS, Hitachi Z −5000; 10−6 g/g detection limit for Cr(III)) with the slit width of 1.3 nm, wavelength of 359.3 nm, lamp current of 9 mA, and air-C2H2 gas mixture flame type. The UV−vis experiments were performed on a UV−vis spectrophotometer (UV-2450, Shimadzu Corporation) with 5 nm slit width.

their accordant chemical property. And a simple and new avenue for synthesizing size controllable and property accordant iron phosphate nanoparticles was established finally.

2. EXPERIMENTAL SECTION 2.1. Materials. For the synthesis of FePO4 nanoparticles, ferric nitrate nonahydrate (Fe(NO3)3·9H2O), ammonium phosphate tribasic ((NH4)3PO4·3H2O), phosphoric acid (H3PO4), and nitric acid (HNO3) with analytical reagent grade were used during the experiments. All of these chemicals were purchased from Sinopharm Chemical Reagent Co., Ltd. and used directly without any further treatment. 2.2. Preparation of FePO4 Nanoparticles. The preparation of FePO4 nanoparticles consists in creating a welldispersed nanoparticle precursor in the microreactor and purification of impurities (mainly Fe2(HPO4)3 here) by thermal aging treatment. Fe(NO3)3·9H2O and an acid mixture solution served as the continuous feed. (NH4)3PO4·3H2O solution was used as the dispersed feed. Driven by the pressure difference between two sides of the dispersion medium, the dispersed feed containing (NH4)3PO4·3H2O was delivered to mix with the continuous feed. The well-dispersed nanoparticle precursor was generated immediately due to the high mass transfer efficiency and well-controlled reaction environment in the micromixing chamber. Then the precursor was aged in an oil bath at 110 °C for the convertion from impurities to FePO4 product. The entire aging process continued under 1200 rpm stirring and atmospheric pressure. Soon afterward, the powders were filtered from the slurry and washed with distilled water at room temperature three times or more. Finally, FePO4 nanoparticle product was obtained after the mixture was dried at 105 °C in air overnight. 2.3. Cr (III) Adsorption Experiments. Cr (III) adsorption experiments were carried out according to Zhang’s work.18 In a typical batch adsorption experiment, a different amount of FePO4 nanoaprticles with different size were added to 30 mL CrCl3·6H2O aqueous solution (Cr3+, 13.6 mg/L). The pH of the solution was adjusted to 5.9 by 0.1 mol/L sodium hydroxide aqueous solution. The quantity of FePO4 nanoparticles of sample 1, sample 2, sample 3, sample 4, and sample 5 was 0.78, 1.05, 1.07, 1.04, and 1.13 g/L, respectively. Then, the mixture was shaken in a 30 °C, 150 rpm oscillating water bath for 48 h. After that, the mixture was separated by 10 min centrifugation at 5000 rpm. The supernatant was carefully taken out and analyzed by atomic absorption spectrometry (AAS) to quantify the residual chromium in the solution. 2.4. Analysis and Characterization. The morphology of as prepared FePO4 nanoparticles was observed by transmission electron microscopy (TEM, JEOL-2010, 120 kV). The nanoparticles were dispersed in ethanol (analytical grade) and dried in air after dripping one/two drop(s) to the TEM grid. Particle size distribution was processed in Image-Pro Plus 6.0 (Media Cybernetics, USA). Phase purity was characterized by XRD (D8-Advance, 40 kV, 40 mA; 3% phase detection limit) using Cu Kα radiation at a 6°/min scanning rate. The powders were calcined from 30 to 400, 500, 600, 800 °C at a heating rate of 10 K/min in air atmosphere. Elemental composition (referring to P and Fe) of the product was determined by an inductively coupled plasma− optical emission spectrometer ICP-OES (IRIS Intrepid II XSP; 10−6 g/g detection limit for P and Fe). For the characterization, the samples were first dissolved in 1:1 volume ratio

3. RESULTS AND DISCUSSION 3.1. Characterization of FePO4 Nanoparticles. To understand the size adjustment of FePO4 nanoparticles, the composition of the continuous feed was adjusted by changing the ratio of nitric acid and phosphoric acid, as shown in Table 1. The concentration of Fe(NO3)3·9H2O and Table 1. Composition and pH Value of the Continuous Feed sample

composition of the continuous feed Fe(NO3)3:HNO3:H3PO4

pH value

1 2 3 4 5

1:1:0 1:0.8:0.2 1:0.5:0.5 1:0.2:0.8 1:0:1

0.90 0.80 0.68 0.65 0.65

(NH4)3PO4·3H2O were both 0.1 mol/L. The pH value of the dispersed feed was 9.10. Two feeds were mixed in the membrane microreactor with equal volume flow rates of 50 mL/min. 3.1.1. Physical Characterizations of FePO4 Nanoparticles. TEM Observation. The dispersity of nanoparticles is significantly important for their applications, which is also difficult to maintain due to high surface energy when the characteristic dimension reduces to the nanoscale. FePO4 nanoparticles produced under different preparation conditions were observed by TEM. All the samples were redispersed by ethanol evaporated before determination. Corresponding different magnification TEM photographs are illustrated in Figure 1. The lower magnification TEM images, shown in the left column, demonstrate that all of the FePO4 nanoparticles produced under different conditions are well dispersed. The higher magnification TEM images, shown in the right column, reveal that the particles are irregular polyhedrons in appearance. Particle Size Distribution. The particles were irregular polyhedron, and we defined the characteristic size of each particle by the hydraulic diameter of its projection on the TEM image. To represent the particle size distribution more accurately, two hundred or more particles with clear boundary in different TEM photographs were counted. For each single particle, three replicate determinations were performed and the average was used as a valid data. The results were shown in Figure 2. As seen, all of the FePO4 particles produced under different conditions have a narrow size distribution range. When H3PO4 concentration gradually increased, average size of B



Article

adsorption, capillary condensation, and external surface adsorption in following. The pore size distribution shown in Figure 3b indicated the existence of mesoporous structure. The average pore size was 18.1, 28.9, 35.0, 44.7, and 31.4 nm when H3PO4 concentration gradually increased. Referring to the TEM images, we considered that the pores were formed by the aggregation of FePO4 nanoparticles. The specific surface area was 153.6 m2/g, 117.9 m2/g, 103.6 m2/g, 87.4 m2/g, and 55.1 m2/g, respectively, with increasing H3PO4 addition, corresponding to the increase of particle size as well. The information of the specific surface area, pore volume, and pore size distribution of FePO4 particles obtained under different preparation conditions are summarized in Table 2. XRD Analysis. The FePO4 nanoparticles require high purity for successful applications since the existence of impurity may deteriorate their performance.33 Thus, XRD analysis was used to check the phase purity of obtained FePO4 nanoparticles. The results are illustrated in Figure 4. With 4 h of calcinations at 400 °C, no diffraction peaks could be detected, suggesting asprepared FePO4 nanoparticles were amorphous. Diffraction peaks gradually emerged when the calcination temperature increases to 500 and 600 °C. After calcination at 800 °C for 4 h, sharp diffraction peaks appear and all of them are in accordance with the standard (JCPDF, file No. 29-0715). No characteristic peak in terms of impurity was observed, indicating the high purity of all the products. ICP-OES Characterization. P/Fe molar ratio is the most important and quantitative index more preferred in industry for judging the purity of FePO4 nanoparticles. Inductively coupled plasma−optical emission spectrometer was used to determine the P/Fe molar ratio of FePO4 nanoparticles as prepared. The results for various samples are listed in Table 3. As seen, P/Fe molar ratios for FePO4 nanoparticles with different sizes were all very close to the stoichiometry value, confirming the nitric and phosphoric acids mixture method could guarantee the purity of FePO4 nanoparticles. Herein, the determination errors of Fe and P were 0.1% for duplicate samples, resulting in the error of the Fe/P ratio of about 0.2%. 3.1.2. Chemical Characterization of FePO4 Nanoparticles. From the above-mentioned physical characterizations of FePO4 nanoparticles as prepared, we may confirm that different sizes of FePO4 nanoparticles prepared with the method we suggested appeared the accordance of some physical properties. However, considering on the size-dependent reactivity, the particles may also require the accordance of chemical properties. In this section, Cr(III) adsorption was used as an indication to evaluate the chemical property of various FePO4 nanoparticles. The results are shown in Table 4, which clearly revealed that Cr(III) adsorption capacity was in proportion to the specific surface area. However, they have nearly the same Cr(III) adsorption capacity (0.182 ± 0.005 mg/m2 adsorbent) when expressing the results as per m2 adsorbent. Cr(III) is specifically adsorbed by FePO4. Thus, these results demonstrate that FePO4 nanoparticles with different sizes have the accordance of the chemical property as well. 3.2. Process Mechanism. To explore the mechanism of size adjustment by mixed phosphoric acid and nitric acid, the continuous feed with specific formula was analyzed by a UV− vis spectrophotometer. The results are shown in Figure 5. For sample 1 where HNO3 was being added to the continuous feed, two absorbance bands at 294.8 and 224.6 nm were observed. These two bands could be attributed to the charge transfer transitions of Fe−O (H2O). When adding H3PO4 to substitute

Figure 1. TEM images of FePO4 nanoparticles produced in the preparation condition of sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d), sample 5 (e). The scale bar is 100 nm for the left column and 20 nm for the right column.

the particles was 9.0, 16.9, 25.8, 33.0 and 50.7 nm, respectively. Corresponding standard deviation is 3.2, 3.1, 4.0, 4.7 and 3.4 nm, respectively. The narrow size distribution was mainly a benefit from the good mixing performance of the membrane microreactor. When two feeds contacted in the microchamber, the mass transfer between the reactants was enhanced dramatically because of the miniaturized mixing scale. As a result, a uniform concentration field propitious to homogeneous nucleation could be achieved instantaneously, which determined the narrow size distribution of FePO4 nanoparticles finally. BET Characterization. The specific surface area, pore volume, and pore size distribution were characterized by a Brunauer−Emmet−Teller analyzer. The adsorption isotherm curve with hysteresis loop at high relative pressure, shown in Figure 3a, was a typical IV type isotherm curve according to International Union of Pure and Applied Chemistry (IUPAC) classification. The process for N2 gas adsorption was a single molecular layer adsorption at first, and the multimolecular layer C



Article

Figure 2. Size distribution of FePO4 nanoparticles. Images a−e correspond to samples from Figure 1. All the statistic results are plotted in image f, including average sizes and deviations as error bars.

for HNO3 gradually, these two bands shift blue. For the case of HNO3 free, these two bands shift to 275.4 and 222.6 nm, respectively. The blue shift phenomenon could be ascribed to an increase of Fe3+ ions coordinating with [HnPO4]−(3‑n) (n = 0, 1, 2). Specifically, the Fe−O (H2O) charge transfer transitions were progressively replaced by Fe−O ([HnPO4]−(3‑n) (n = 0, 1, 2)).

The change of the existing state of iron ions in the continuous feed has direct effect on the precipitation reaction for generating iron phosphate precursors in the microreactor, which would further influence the original growth of the particles, the particle purification, and their aging stage. In detail, when HNO3 is added into the continuous feed containing Fe(NO3)3·9H2O, more free Fe3+ may be supplied. The fast precipitation, as illustrated in reaction 1, conducted D



Article

Figure 3. (a) A typical adsorption isotherm curve of as-prepared FePO4 nanoparticles and (b) pore size distribution of various samples.

Table 2. Summary of BET Results of Various Samples sample

specific surface area (m2/g)

pore volume (cc/g)

average pore size (nm)

1 2 3 4 5

153.6 117.9 103.6 87.4 55.1

1.39 0.77 0.91 0.98 0.99

18.1 28.9 35.0 44.7 31.4

Table 4. Cr (III) Adsorption Determination Using FePO4 Nanoparticles with Various Sizes Cr (III) concentration (mg/L) sample 1 2 3 4 5

Figure 4. XRD spectra of FePO4 products after calcinations. From bottom to top corresponds to sample 1 at 400, 500, 600, 800 °C, and sample 2, sample 3, sample 4 and sample 5 at 800 °C, respectively.

P, wt %

Fe, wt %

P/Fe, molar ratio

1 2 3 4 5

17.44 16.89 16.94 17.28 16.16

31.17 30.23 30.56 30.21 28.58

1.009 1.008 1.001 1.033 1.021

initial

residual

(mg/g adsorbent)

(mg/m2 adsorbent)

38.66

17.07 16.94 17.87 22.27 27.02

27.67 20.63 19.50 15.81 10.28

0.180 0.175 0.188 0.181 0.186

Figure 5. The UV−vis results for continuous feed with various compositions. The inset is the enlarged image for the left absorbance bands. The curves from the bottom to top corresponds to sample 1, sample 2, sample 3, sample 4, and sample 5, respectively.

Table 3. P/Fe Molar Ratio for Different Size FePO4 Nanoparticles sample

adsorption capacity

free Fe3+ concentration decreases due to coordination effect of Fe3+ with [HnPO4]−(3‑n) (n = 0, 1, 2). The size of primary iron phosphate particles increases because of the gradual decrease of the supersaturation ratio of iron phosphate. Moreover, the amount of Fe2(HPO4)3 also may increase with the addition of H3PO4. When the precursors are treated by thermal aging for product purification, the growth of primary particles originating from the impurity conversion would make them even bigger. All in all, the fine size adjustment of FePO4 nanoparticles could be achieved in a comparatively wide range (9−50 nm in this work) by carefully adjusting the composition of mixed H3PO4 and HNO3 in the continuous feed.

mostly in the microreactor, will generate primary iron phosphate particles with smaller size. The generation of Fe2(HPO4)3, shown as reaction 2, will be inhibited due to more iron source being consumed by reaction 1. Furthermore, the increasing size of primary iron phosphate particles resulting from impurity transfer (FePO4 is more stable than Fe2(HPO4)3 at high temperature), shown as reaction 3, will be also limited. Vice versa, with H3PO4 addition to the continuous feed, the

Fe3 + + PO4 3 − → FePO4 E

(1)



Article

Table 5. Contrast of Various Techniques for Nanosized Iron Phosphate Preparation technique

advantage

disadvantage

precipitation

simple, widely used

oxidation flame spray pyrolysis

easy for small particles preparation advance in small, dense and spherical particles preparation, relatively narrow size distribution crystal nanoparticles, high purity high purity, narrow size distribution, size adjustment in the range of 9−50 nm

electrochemical synthesis our technique

Fe3 + + [HnPO4 ]−(3 − n) (n = 0, 1, 2) → Fe2(HPO4 )3

(2)

Fe2(HPO4 )3 → 2FePO4 ↓ +H3PO4

(3)

wide size distribution, poor and unstable purity poor in dispersity and purity poor purity, large consumption of fuel gas and oxygen heavy aggregation of products relatively narrow range for size adjusting

reference 13, 28, 34−37 38, 39 22 40 this work

4. CONCLUSION On the basis of the general platform of coupling fast precipitation in a microreactor and thermal treatment process, we successfully developed a new and simple way for preparing FePO4 nanoparticles with controllable size in the range from 9 to 50 nm. The goal was achieved by the strategy of adjusting the degree of supersaturation of FePO4 during the fast precipitation process in the microreactor. Specifically, the change of actual concentration of free Fe3+ participating in the fast precipitation reaction was directed by adjusting the mixture of nitric acid and phosphoric acid in the continuous fluid. Characterizations of TEM, XRD, BET, ICP-OES, and Cr(III) adsorption confirmed that these size controllable FePO4 nanoparticles were pure, well dispersed, narrowly sizedistributed, and property accordant. The effect of mixed acids on species with respect to iron was also checked by UV−vis determination. The technique is general with respect to various acids being able to coordinate with Fe3+ and can be potentially scaled-up for producing pure, property accordant FePO4 nanoparticles with controllable size and narrow size distribution.

3.3. Comparisons with Similar Techniques. In this section, we give a detailed contrast of various iron phosphate preparation techniques reported with aspects of the controllability of size, size distribution, and purity of the product. Table 5 shows them briefly. Traditional precipitation34−36 is a fairly simple and widely used way for nanosized iron phosphate preparation. However, big bulks of the product, wide size distribution, and unstable purity are the cost of its simplicity. Though developments have been made by controlling the solution environment, like using various templates/surfactants to hinder the aggregation,13,28,37 problems still remain including the difficulties in controlling the microprecipitation environment in a macro-reactor, removal of used organics, and increasing production efficiency. The oxidation method38,39 could easily fabricate iron phosphate nanoparticles below 100 nm, but the relatively high price of ferrite and strict requirement of an oxygen-free environment have limited its popularization. Iron phosphate nanoparticles generated by this technique usually perform poorly in dispersity (mainly form a sponge-like structure) and purity (impurities include Fe2O3, Fe4(P2O7)3, etc). The flame spray pyrolysis22 technique shows an advance in fabricating small, dense, and spherical iron phosphate nanoparticles. And the size distribution is also relatively narrow. However, the product is not pure with a P/Fe molar ratio around 0.94, and large consumption of fuel gas and oxygen is a common problem to such a technique. The electrochemical synthesis method40 brings a new way to prepare crystal iron phosphate nanoparticles with high purity (P/Fe = 1.00), but it contains a high temperature calcination step (600 °C) for the conversion of Fe(OH)HPO4 precursor nanoparticles to iron phosphate, which would lead to the fusion and heavy aggregation of the final product. Moreover, the size adjustment of iron phosphate nanoparticles is difficult and rarely reported for all of the above-mentioned techniques. Our technique takes advantage of the simplicity of a traditional precipitation method and overcomes its drawbacks by using a microreactor to control the precipitation environment at the microscale to produce a uniform and well-dispersed precursor. The coupled thermal treatment at relatively low temperature could not only convert impurities, but also could inherit the excellent property of the precursor. Additionally, through gradually changing the composition of continuous fluid, the size of iron phosphate could easily be regulated in the range of 9−50 nm. Therefore, we can expect more facile and diversified industrial applications.

■

AUTHOR INFORMATION

Corresponding Author

* Tel.: +86 10 62773017. Fax: +86 10 62770304. E-mail: luyc@ tsinghua.edu.cn. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS

■

REFERENCES

The authors gratefully acknowledge the support of the National Natural Science Foundation of China (21036002, 21176136) and National Science and Technology Support Program of China (2011BAC06B01) on this work.

(1) Segets, D.; Gradl, J.; Taylor, R. K.; Vassilev, V.; Peukert, W. Analysis of optical absorbance spectra for the determination of ZnO nanoparticle size distribution, solubility, and surface energy. ACS Nano 2009, 3, 1703. (2) Segets, D.; Harting, M. A. J.; Gradl, J.; Peukert, W. A population balance model of quantum dot formation: Oriented growth and ripening of ZnO. Chem. Eng. Sci. 2012, 70, 4. (3) Son, S. U.; Jang, Y.; Yoon, K. Y.; Kang, E.; Hyeon, T. Facile synthesis of various phosphine-stabilized monodisperse palladium nanoparticles through the understanding of coordination chemistry of the nanoparticles. Nano lett 2004, 4, 1147. (4) Sen, T.; Patra, A. Recent advances in energy transfer processes in gold-nanoparticle based assemblies. J. Phys. Chem. C 2012, 116, 17307. (5) Zhu, Y.; Qian, H. F.; Jin, R. C. Catalysis opportunities of atomically precise gold nanoclusters. J. Mater. Chem. 2011, 21, 6793.

F



Article

(6) Hamada, K.; Kaneko, T.; Chen, M. Q.; Akashi, M. Size-selective material adsorption property of polymeric nanoparticles with projection coronas. Chem. Mater. 2007, 19, 1044. (7) Kirubaharan, C. J.; Kalpana, D.; Lee, Y. S.; Kim, A. R.; Yoo, D. J.; Nahm, K. S.; Kumar, G. G. Biomediated silver nanoparticles for the highly selective copper (II) ion sensor application. Ind. Eng. Chem. Res. 2012, 51, 7441. (8) Selvan, S. T.; Yang Tan, T. T.; Yi, D. K.; Jana, N. R. Functional and multifunctional nanoparticles for bioimaging and biosensing. Langmuir 2011, 26, 11631. (9) Oh, W. - K.; Yoon, H.; Jang, J. Size control of magnetic carbon nanoparticles for drug delivery. Biomaterials 2010, 31, 1342. (10) Kelly, K. L.; Coronado, E.; Zhao, L. L.; Schatz, G. C. The optical properties of metal nanoparticles: The influence of size, shape, and dielectric environment. J. Phys. Chem. B 2003, 107, 668. (11) Yang, S. K.; Cai, W. P.; Zhang, H. W.; Xu, X. X.; Zeng, H. B. Size and structure control of Si nanoparticles by laser ablation in different liquid media and further centrifugation classification. J. Phys. Chem. C 2009, 113, 19091. (12) Masquelier, P.; Reale, C.; Wurm, M.; Morerette, L.; Dupont, D. L. Hydrated iron phosphates FePO4·nH2O and Fe4(P2O7)3·nH2O as 3V positive electrodes in rechargeable lithium batteries. J. Electrochem. Soc. 2002, 149, A1037. (13) Son, D.; Kim, E.; Kim, T. G.; Kim, M. G.; Cho, J.; Park, B. Nanoparticle iron phosphate anode material for Li-ion battery. Appl. Phys. Lett. 2004, 85, 5875. (14) Zaghib, K.; Julien, C. M. Structure and electrochemistry of FePO4·2H2O hydrate. J. Power Sources 2005, 142, 279. (15) Wang, X. X.; Wang, Y.; Tang, Q. H.; Guo, Q. A.; Zhang, Q. H.; Wan, H. L. MCM-41- supported iron phosphate catalyst for partial oxidation of methane to oxygenates with oxygen and nitrous oxide. J. Catal. 2003, 217, 457. (16) Wang, Y.; Wang, X. X.; Su, Z.; Tang, Q. H.; Zhang, Q. H.; Wan, H. L. SBA-15-supported iron phosphate catalyst for partial oxidation of methane to formaldehyde. Catal. Today 2004, 93−95, 155. (17) Ren, T.; Yan, L.; Zhang, X. M.; Suo, J. H. Selective oxidation of benzene to phenol with N2O by unsupported and supported FePO4 catalysts. Appl. Catal. A: General 2003, 244, 11. (18) Zhang, X. X.; Tang, S. S.; Chen, M. L.; Wang, J. H. Iron phosphate as a novel sorbent for selective adsorption of chromium (III) and chromium speciation with detection by ETAAS. J. Anal. At. Spectrom. 2012, 27, 466−472. (19) Mustafa, S.; Naeem, A.; Murtaza, S.; Rehana, N.; Samad, H. Y. Comparative sorption properties of metal (III) phosphate. J. Colloid Interface Sci. 1999, 220, 63. (20) Benmokhtar, S.; Belmal, H.; Jazouli, A. E.; Chaminade, J. P.; Gravereau, P.; Pechev, S.; Grenier, J. C.; Villeneuve, G.; Waal, D. Synthesis, structure, and physicochemical investigations of the new α Cu0.50TiO(PO4) oxyphophate. J. Solid State Chem. 2007, 180, 772. (21) Lai, Y. M.; Liang, X. F.; Yang, S. Y.; Wang, J. X.; Cao, L. H.; Dai, B. Raman and FTIR spectra of iron phosphate glasses containing cerium. J. Mol. Struct. 2011, 992, 84. (22) Rohner, F.; Ernst, F. O.; Arnold, M.; Hilbe, M.; Biebinger, R.; Ehrensperger, F. S.; Pratsinis, E.; Langhans, W.; Hurrell, R. F.; Zimmermann, M. B. Synthesis, characterization, and bioavailability in rats of fettic phosphate nanoparticles. J. Nutr. 2007, 137, 614. (23) Yamada, A.; Chung, S. C.; Hinokuma, K. Optimized LiFePO4 for lithium battery cathodes. J. Electrochem. Soc. 2001, 148, A224. (24) Gaberscek, M.; Domiko, R.; Jamnik, J. Is small particle size more important than carbon coating? An example study on LiFePO4 cathodes. Electrochem. Commun. 2007, 9, 2778. (25) Huang, Y. H.; Ren, H. B.; Yin, S. Y.; Wang, Y. H.; Peng, Z. H.; Zhou, Y. H. Synthesis of LiFePO4/C composite with high-rate performance by starch sol assisted rheological phase method. J. Power Sources 2010, 195, 610. (26) Guo, X. F.; Ding, W. W.; Chen, H.; Yan, Q. J. Preparation and characterization of nanosized Fe-P-O catalyst. J. Fuel Chem. Technol. 2000, 28, 385.

(27) Lu, Y. C.; Zhang, T. B.; Liu, Y.; Luo, G. S. Preparation of FePO4 nano-particles by coupling fast precipitation in membrane dispersion microcontactor and hydrothermal treatment. Chem. Eng. J. 2012, 210, 18. (28) Yin, Y. J.; Zhang, H.; Wu, P.; Zhou, B.; Cai, C. X. Iron phosphate nanostructures synthesized by microwave method and their applications in biosensing. Nanotechnology 2010, 21, 1. (29) Zhao, J. M.; Ma, J.; Jian, Z. L.; Hu, Y. S.; Liu, H. Z. A general phase-transfer protocol for mineral for mineral acids and its application in the large-scale synthesis of highly nanoporous iron phosphate in nonaqueous solvent. Ind. Eng. Chem. Res. 2012, 51, 12025. (30) Shi, Z. C.; Attia, A.; Ye, W. L.; Wang, Q.; Li, Y. X.; Yang, Y. Synthesis, characterization and electrochemical performance of mesoporous FePO4 as cathode material for rechargeable lithium batteries. Electrochim. Acta 2008, 53, 2665. (31) Shi, Z. C.; Li, Y. X.; Ye, W. L.; Yang, Y. Mesoporous FePO4 with enhanced electrochemical performance as cathode materials of rechargeable lithium batteries. Electrochem. Solid-State Lett. 2005, 8, A396. (32) Escoda, M. L.; Torre, F. D.; Salvado, V. The formation of mixed ligand complexes of Fe (III) with phosphoric and citric acids in 0.5 M NaNO3 aqueous solutions. Polyhedron 1999, 18, 3269. (33) Padhi, A. K.; Nanjundaswamy, K. S.; Okada, S.; Goodenough, J. B. Effect of structure on the Fe3+/Fe2+ redox couple in iron phosphate. J. Electrochem. Soc. 1997, 144, 1609. (34) Zhou, W. J.; He, W.; Zhang, X. D.; Yan, S. P.; Sun, X. N.; Tian, X. Y.; Han, X. X. Biosynthesis of iron phosphate nanopowders. Powder Technol. 2009, 194, 106. (35) Nagaraju, P.; Srilakshmi, Ch.; Pasha, N.; Lingaiah, N.; Suryanarayana, I.; Sai Prasad, P. S. Effect of method of preparation on the activity and selectivity of iron phosphate catalyst in the ammoxidation of 2-methyl pyrazine. Catal. Today 2008, 131, 393. (36) He, W.; Zhou, W. J.; Wang, Y. J.; Zhang, X. D.; Zhao, H. S.; Li, Z. M.; Yan, S. P. Biomineralization of iron phosphate nanoparticles in yeast cells. Mater. Sci. Eng. C 2009, 29, 1348. (37) Yang, H. J.; Song, H. J.; Shin, H. J. A rapid synthesis of iron phosphate nanoparticles via surface-mediated spontaneous reaction for the growth of high-yield, single-walled carbon nanotubes. Langmuir 2005, 21, 9098. (38) Wang, X.; Yang, X. H.; Zheng, H. G.; Jin, J. Y.; Zhang, Z. D. Synthesis and electrochemical performance of amorphous hydrated iron phosphate nanoparticles. J. Cryst. Growth 2005, 274, 241. (39) Prosini, P. P.; Lisi, M.; Scaccia, S.; Carewaka, M.; Cardellini, F.; Pasquali, M. Synthesis and characterization of amorphous hydrated FePO4 and its electrode performance in lithium batteries. J. Electrochem. Soc. 2002, 149, A297. (40) Liu, H. C.; Ho, W. H.; Li, C. F.; Yen, S. K. Electrochemical synthesis of FePO4 for anodes in rechargeable lithium batteries. J. Electrochem. Soc. 2008, 155, E178.

G


Size Adjustment of Iron Phosphate Nanoparticles by Using Mixed

Recommend Documents