Shuttle-like supramolecular nanostructures formed by self-assembly of a porphyrin via an oil/water system
© Guo et al; licensee Springer. 2011
Received: 19 July 2011
Accepted: 23 September 2011
Published: 23 September 2011
In this paper, in terms of the concentration of an aqueous solution of a surfactant, we investigate the self-assembly behavior of a porphyrin, 5, 10, 15, 20-tetra(4-pyridyl)-21H, 23H-porphine [H2TPyP], by using an oil/water system as the medium. We find that when a chloroform solution of H2TPyP is dropwise added into an aqueous solution of cetyltrimethylammonium bromide [CTAB] with a lower concentration, a large amount of irregular nanoarchitectures, together with a small amount of well-defined shuttle-like nanostructures, hollow nanospheres, and nanotubes, could be produced. While a moderate amount of shuttle-like nanostructures accompanied by a few irregular nanoarchitectures, solid nanospheres, and nanorods are produced when a CTAB aqueous solution in moderate concentration is employed, in contrast, a great quantity of shuttle-like nanostructures together with a negligible amount of solid nanospheres, nanofibers, and irregular nanostructures are manufactured when a high-concentration CTAB aqueous solution is involved. An explanation on the basis of the molecular geometry of H2TPyP and in terms of the intermolecular π-π interactions between H2TPyP units, and hydrophobic interactions between CTAB and H2TPyP has been proposed. The investigation gives deep insights into the self-assembly behavior of porphyrins in an oil/water system and provides important clues concerning the design of appropriate porphyrins when related subjects are addressed. Our investigation suggests that an oil/aqueous system might be an efficient medium for producing unique organic-based nanostructures.
Currently, tremendous efforts have been devoted to open up various facile methodologies for the fabrication of nanostructured materials with novel morphologies since the fascinating architectures and the unique physicochemical properties of the produced nanomaterials make them of considerable interest as promising components for chemical/biochemical sensors, opto- and nano-electronic devices, bionanotechnology, and so forth [1–14]. Among various nanostructured materials, those with well-defined discrete architectures, typically exemplified by nanofibers, nanotubes, nanorods, nanospheres, nanocubes, etc., have so far been intensively investigated [1–14]. Besides these sophisticated typical nanomaterials, those with complicated yet well-defined morphologies, for example, cauliflower-like nanostructures, nanopolyhedrons, nanotetrapods, nanosprings, nanospirals, nanospindles, nanoshuttles, etc. [15–30], have also attracted much attention owing to their extraordinary physicochemical properties. With respect to this issue, a paramount of inorganic-based systems have been developed [1–6, 15–24], while examples in terms of organic-based systems are relatively fewer [4–6, 10, 11]. As a matter of fact, in contrast to inorganic nanomaterials [1–6], organic nanostructures have peculiar electronic and optical properties and can render impressive varieties and flexibilities in molecular design and tunability of physicochemical properties [7–14]. This makes the organic-based nanostructures promising candidates for nanoscience and nanotechnology. Consequently, an exploration on the fabrication of organic nanostructures with unique yet well-defined morphologies should be an important issue to be explored intensively.
When considering the fabrication of organic-based nanostructured materials, supramolecular assembly, which aims at manufacturing sophisticated, organized molecular associations through various non-covalent interactions, including π-π interactions, hydrophobic interactions, electrostatic interactions, etc., has currently been demonstrated to be an excellent strategy. It provides fertile, new, and promising opportunities for nanoscience and nanotechnology, material science, biological science, and so on [7–14, 31]. Various fascinating organic-based nanomaterials have so far been manufactured in terms of diverse solution-based self-assembly technique, template-induced self-assembly process, physical vapor deposition, etc. [7–14, 25–30], where the surfactant-assisted self-assembly [SASA] has been considered to be an important solution-based method owing to its nice adaptability, simplicity, and reproducibility [32, 33].
Among various building blocks for the fabrication of supramolecular nanostructures, porphyrins have been reported to be one of the most useful units. This is promoted by their multifunctionality, biocompatibility, flexible and tunable molecular structure by chemical modification, rigid and planar molecular skeleton, which make porphyrin-involved nanomaterials have rich assembly, physicochemical and biochemical properties [26, 27, 29, 32–39]. For example, we have recently demonstrated that a metal porphyrin, zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H, 23H-porphine [ZnTPyP], could be organized to form various well-defined nanostructures in a controllable manner via a SASA method through an oil/water system . In that case, we showed that depending on the aging time and the concentration of the aqueous solution of the surfactant, cetyltrimethylammonium bromide [CTAB], hollow or solid nanospheres, nanotubes, nanorods, and nanofibers could be facilely obtained. Therein, we suggested that the intermolecular π-π interactions between ZnTPyP units together with the hydrophobic interactions between ZnTPyP and CTAB played an important role during the assembly process.
On the basis of the aforementioned brief review, we herein investigate the assembly behavior of H2TPyP via a process similar to that for ZnTPyP . We find that a large amount of irregular nanoarchitectures, together with a small amount of shuttle-like nanostructures, hollow nanospheres, and nanotubes, could be produced using a lower concentration of a CTAB aqueous solution. When a CTAB aqueous solution with a moderate concentration is used, a moderate amount of shuttle-like nanostructures accompanied by a few irregular nanoarchitectures, solid nanospheres, and nanorods could be produced, while a good quantity of shuttle-like nanostructures, together with a very small amount of solid nanospheres, nanofibers, and a negligible amount of irregular nanostructures could be predominantly manufactured when a high-concentration CTAB aqueous solution is employed. An explanation on the basis of the molecular geometry of H2TPyP and in terms of the intermolecular π-π interactions between H2TPyP molecules and the hydrophobic interactions between CTAB and H2TPyP has been proposed. Although various porphyrin-involved organic nanostructures [26, 27, 29, 32–39] and inorganic shuttle-like nanostructures have been previously produced [22–24], this might be the first example showing that porphyrin-based shuttle-like nanoarchitectures could be facilely produced via an oil/water medium. The study gives deep insights into the self-assembly behavior of porphyrins in an oil/water system and provides important clues to the designing of appropriate porphyrins when related subjects are addressed.
Chemicals and reagents
CTAB (99%, Alfa Aesar) and H2TPyP (97%, Aldrich) were used as received without further purification. Milli-Q water (18 MΩ cm) and distilled chloroform were used as the solvents for CTAB and H2TPyP, respectively.
Methods and procedures
The process for the synthesis of H2TPyP-based nanostructures via the oil/water medium is similar to those described for ZnTPyP . Typically, 400 μL of a chloroform solution of H2TPyP (2 × 10-4 M) was added dropwise into a 10-mL aqueous solution of CTAB under vigorous magnetic stirring within 1 to 2 min. The concentrations of the CTAB aqueous solutions were 0.225, 0.9, and 4.5 mM for the samples named as I, II, and III, respectively. Soon after adding H2TPyP chloroform solution, an opaque solution was obtained; a transparent yellowish solution was obtained after vigorous stirring was maintained for 15 min, as shown in Figure 1. The solution was then kept at room temperature without disturbing for a desired time for aging, after which the UV/vis spectra of the solutions were measured. The formed nanostructures were dramatically washed with Milli-Q water several times via repeating filtration or centrifugation, after which they were subjected to various characterizations. The Millipore filter (Whatman) used for the filtration has a pore size of 200 nm. In the case of centrifugation, a rotation speed of 10, 000 rpm is adopted. We found that similar results could be obtained for the samples washed by these two methods. Subsequently, the nanostructures were characterized by low-resolution transmission electron microscopy [LRTEM], high-resolution transmission electron microscopy [HRTEM], fast Fourier transformation [FFT], energy-dispersive X-ray spectroscopy [EDX], and scanning electron microscopy [SEM].
A JASCO UV-550 spectropolarimeter was used for the UV/vis spectral investigation. The SEM measurements were performed using a Hitachi S-4800 system. The LRTEM and HRTEM images of the nanostructures were obtained with a FEI Tecnai G2 F20 U-TWIN, where the accelerating voltages were set as 200 and 80 kV, respectively. Elemental analysis was achieved using energy-dispersive X-ray spectroscopy on the FEI Tecnai G2 F20 U-TWIN.
Results and discussions
SEM images of H2TPyP-involved nanostructures
UV/vis spectra of H2TPyP-involved nanostructures
TEM images of H2TPyP-involved nanostructures
Moreover, in order to reveal the internal structure of our shuttle-like nanoarchitectures, their HRTEM and FFT images were investigated, respectively. During the experiments, we found that our organic nanostructures suffer a fast amorphization under the strong electron beam (with an accelerating voltage of 200 kV) illumination. Therefore, the HRTEM was carried out with an accelerating voltage of 80 kV, where it was find that amorphization could be decelerated to some extent. As shown in the middle and bottom panels of Figure 5, distinct lattice fringes could be detected from all of the formulated shuttle-like nanoarchitectures. An interlattic spacing of about 1 nm could be obtained, as indicated by the FFT analysis. This value is very close to the side length of H2TPyP square, which was calculated to be approximately 1.1 nm. Accompanied by information deduced from the UV/vis spectra, these results suggest that our shuttle-like nanostructures are essentially composed of H-type molecule associations.
An explanation for the formation of the shuttle-like supramolecular nanostructures
It has been demonstrated that the formation of a porphyrin/surfactant complex is facilitated primarily by the electrostatic or hydrophobic interactions between these two components [46–49]. In the case of ionic porphyrin/nonionic surfactant or nonionic porphyrin/ionic surfactant systems, the hydrophobic interactions between the alkyl chain of the surfactant and the π system of porphyrin play an essential role [32, 46, 47]. In our present case, the employed porphyrin is a nonionic compound. Consequently, the electrostatic interactions between porphyrin and the surfactant are negligible. Thus, we could simply propose that three kinds of intermolecular interactions, i.e., π-π interactions between porphyrin molecules (H2TPyP/H2TPyP), hydrophobic interactions between porphyrin and CTAB molecules (H2TPyP/CTAB), and CTAB/CTAB interactions, compete with each other during the SASA process.
As has been demonstrated, for zinc porphyrins, owing to the large size of the zinc cation, Zn generally stands out from the mean macrocyclic plane of porphyrin, and instead of a planar geometry, zinc porphyrin always exhibits a bent molecular geometry [50, 51]. This could cause a somewhat steric hindrance between zinc porphyrin molecules when they are assembled through intermolecular π-π interactions . Previously, our experimental facts suggested that the ZnTPyP molecule formed a ZnTPyP/CTAB complex with CTAB through the intermolecular hydrophobic interactions between the alkyl chain of CTAB and the π system of ZnTPyP upon coming into contact with CTAB . This was a result of the dynamic competition between the aforementioned three types of intermolecular interactions. After this, owing to their thermodynamic superiority, ZnTPyP units formed assemblies via π-π interactions gradually during the aging, resulting in the formation of various well-defined nanostructures .
At the same time, it should also be pointed out that, still, a small amount of H2TPyP molecules could act as ZnTPyP during the SASA since small amounts of hollow nanospheres and nanotubes, solid nanospheres and nanorods, and solid nanospheres and nanofibers, which are predominately formed in the corresponding samples of ZnTPyP systems, could after all be observed from samples I, II, and III of H2TPyP, respectively.
In summary, we have shown that when a surfactant aqueous solution with an appropriate concentration is selected, a free-base porphyrin, H2TPyP, could be assembled to predominately form unique yet well-defined shuttle-like nanoarchitectures via SASA in an oil/water medium. This might be the first report of porphyrin-based shuttle-like nanoarchitectures which could be facilely produced. By taking into account the molecular geometry of H2TPyP, the intermolecular non-covalent interactions, as well as the role of the surfactant, a possible explanation has been proposed. It gives deep insights into the self-assembly behavior of porphyrins in an oil/water system and provides important clues concerning the design of appropriate porphyrins when related subjects are addressed. Our investigation suggests that an oil/aqueous system might be an efficient medium for producing organic-based nanostructures with unique yet well-defined morphologies.
5, 10, 15, 20-tetra(4-pyridyl)-21H, 23H-porphine
zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H, 23H-porphine
low-resolution transmission electron microscopy
high-resolution transmission electron microscopy
fast Fourier transformation
energy-dispersive X-ray spectroscopy
scanning electron microscopy.
We thank the National Natural Science Foundation of China (20773141, 20873159 and 21021003), National Key Basic Research Project of China (2007CB808005 and 2011CB932301), and the Chinese Academy of Sciences for financial support.
- El-Sayed MA: Some interesting properties of metals confined in time and nanometer space of different shapes. Acc Chem Res 2001, 34: 257. 10.1021/ar960016nView ArticleGoogle Scholar
- Hurst SJ, Payne EK, Qin L, Mirkin CA: Multisegmented one-dimensional nanorods prepared by hard-template synthetic methods. Angew Chem Int Ed 2006, 45: 2672. 10.1002/anie.200504025View ArticleGoogle Scholar
- Tian B, Kempa TJ, Lieber CM: Single nanowire photovoltaics. Chem Soc Rev 2009, 38: 16. 10.1039/b718703nView ArticleGoogle Scholar
- Tenne R: Inorganic nanotubes and fullerene-like nanoparticles. Nat Nanotechnol 2006, 1: 103. 10.1038/nnano.2006.62View ArticleGoogle Scholar
- Heath JR: Superlattice nanowire pattern transfer. Acc Chem Res 2008, 41: 1609. 10.1021/ar800015yView ArticleGoogle Scholar
- Jiea J, Zhang W, Bello I, Lee C-S, Lee S-T: One-dimensional II-VI nanostructures: synthesis, properties and optoelectronic applications. Nano Today 2010, 5: 313. 10.1016/j.nantod.2010.06.009View ArticleGoogle Scholar
- Shimizu T, Masuda M, Minamikawa H: Supramolecular nanotube architectures based on amphiphilic molecules. Chem Rev 2005, 105: 1401. 10.1021/cr030072jView ArticleGoogle Scholar
- Zang L, Che Y, Moore JS: One-dimensional self-assembly of planar π-conjugated molecules: adaptable building blocks for organic nanodevices. Acc Chem Res 2008, 41: 1596. 10.1021/ar800030wView ArticleGoogle Scholar
- Ulijn RV, Smith AM: Designing peptide based nanomaterials. Chem Soc Rev 2008, 37: 664. 10.1039/b609047hView ArticleGoogle Scholar
- Yamamoto T, Fukushima T, Aida T: Self-assembled nanotubes and nanocoils from π-conjugated building blocks. Adv Polym Sci 2008, 220: 1.Google Scholar
- Palmer LC, Stupp SI: Molecular self-assembly into one-dimensional nanostructures. Acc Chem Res 2008, 41: 1674. 10.1021/ar8000926View ArticleGoogle Scholar
- Numata M, Shinkai S: Self-assembled polysaccharide nanotubes generated from β-1, 3-glucan polysaccharides. Adv Polym Sci 2008, 220: 65.Google Scholar
- Toksöz S, Guler MO: Self-assembled peptidic nanostructures. Nano Today 2009, 4: 458. 10.1016/j.nantod.2009.09.002View ArticleGoogle Scholar
- Zhao YS, Fu H, Peng A, Ma Y, Liao Q, Yao J: Construction and optoelectronic properties of organic one-dimensional nanostructures. Acc Chem Res 2010, 43: 409. 10.1021/ar900219nView ArticleGoogle Scholar
- Mulvihill MJ, Ling XY, Henzie J, Yang P: Anisotropic etching of silver nanoparticles for plasmonic structures capable of single-particle SERS. J Am Chem Soc 2010, 132: 268. 10.1021/ja906954fView ArticleGoogle Scholar
- Zhuang Z, Lu X, Peng Q, Li Y: Direct synthesis of water-soluble ultrathin CdS nanorods and reversible tuning of the solubility by alkalinity. J Am Chem Soc 2010, 132: 1819. 10.1021/ja909776gView ArticleGoogle Scholar
- Pang M, Hu J, Zeng HC: Synthesis, morphological control, and antibacterial properties of hollow/solid Ag 2 S/Ag heterodimers. J Am Chem Soc 2010, 132: 10771. 10.1021/ja102105qView ArticleGoogle Scholar
- Yang Y, Jin Y, He H, Wang Q, Tu Y, Lu H, Ye Z: Dopant-induced shape evolution of colloidal nanocrystals: the case of zinc oxide. J Am Chem Soc 2010, 132: 13381. 10.1021/ja103956pView ArticleGoogle Scholar
- Rao CN, Kalyanikutty KP: The liquid-liquid interface as a medium to generate nanocrystalline films of inorganic materials. Acc Chem Res 2008, 41: 489. 10.1021/ar700192dView ArticleGoogle Scholar
- Yan H, He R, Pham J, Yang P: Morphogenesis of one-dimensional ZnO nano- and microcrystals. Adv Mater 2003, 15: 402. 10.1002/adma.200390091View ArticleGoogle Scholar
- Raula M, Rashid MH, Paira TK, Dinda E, Mandal TK: Ascorbate assisted growth of hierarchical ZnO nanostructures: sphere, spindle, flower and their catalytic properties. Langmuir 2010, 26: 8769. 10.1021/la904507qView ArticleGoogle Scholar
- Wang H, Shao W, Gu F, Zhang L, Lu M, Li C: Synthesis of anatase TiO 2 nanoshuttles by self-sacrificing of titanate nanowires. Inorg Chem 2009, 48: 9732. 10.1021/ic901235nView ArticleGoogle Scholar
- Peng WQ, Cong GW, Qu SC, Wang ZG: Synthesis of shuttle-like ZnO nanostructures from precursor ZnS nanoparticles. Nanotechnology 2005, 16: 1469. 10.1088/0957-4484/16/9/008View ArticleGoogle Scholar
- Liu X-M, Fu S-Y, Xiao H-M, Huang C-J: Preparation and characterization of shuttle-like α-Fe 2 O 3 nanoparticles by supermolecular template. J Solid State Chem 2005, 178: 2798. 10.1016/j.jssc.2005.06.018View ArticleGoogle Scholar
- Zhang Y, Chen P, Jiang L, Hu W, Liu M: Controllable fabrication of supramolecular nanocoils and nanoribbons and their morphology-dependent photoswitching. J Am Chem Soc 2009, 131: 2756. 10.1021/ja805891kView ArticleGoogle Scholar
- Huang C, Wen L, Liu H, Li Y, Liu X, Yuan M, Zhai J, Jiang L, Zhu D: Controllable growth zero to multi-dimensional nanostructures of a novel porphyrin molecule. Adv Mater 2009, 21: 1721. 10.1002/adma.200802114View ArticleGoogle Scholar
- Huang C, Li Y, Yang J, Cheng N, Liu H, Li Y: Construction of multidimensional nanostructures by self-assembly of a porphyrin analogue. Chem Commun 2010, 46: 3161. 10.1039/b927059kView ArticleGoogle Scholar
- Chen P, Ma X, Zhang Y, Hu K, Liu M: Nanofibers and nanospirals fabricated through the interfacial organization of a partially fluorinated compound. Langmuir 2007, 23: 11100. 10.1021/la701383yView ArticleGoogle Scholar
- Martin KE, Wang Z, Busani T, Garcia RM, Chen Z, Jiang Y, Song Y, Jacobsen JL, Vu TT, Schore NE, Swartzentruber BS, Medforth CJ, Shelnutt JA: Donor-acceptor biomorphs from the ionic self-assembly of porphyrins. J Am Chem Soc 2010, 132: 8194. 10.1021/ja102194xView ArticleGoogle Scholar
- Liu B, Chen M, Nakamura C, Miyake J, Qian D-J: Coordination polymer nanocombs self-assembled at the water-chloroform interface. New J Chem 2007, 31: 1007. 10.1039/b701839hView ArticleGoogle Scholar
- Lehn JM: Toward complex matter: supramolecular chemistry and self-organization. Proc Natl Acad Sci USA 2002, 99: 4763. 10.1073/pnas.072065599View ArticleGoogle Scholar
- Hu JS, Guo YG, Liang HP, Wan LJ, Jiang L: Three-dimensional self-organization of supramolecular self-assembled porphyrin hollow hexagonal nanoprisms. J Am Chem Soc 2005, 127: 17090. 10.1021/ja0553912View ArticleGoogle Scholar
- Lee SJ, Hupp JT, Nguyen ST: Growth of narrowly dispersed porphyrin nanowires and their hierarchical assembly into macroscopic columns. J Am Chem Soc 2008, 130: 9632. 10.1021/ja801733tView ArticleGoogle Scholar
- Wang Z, Li Z, Medforth CJ, Shelnutt JA: Self-assembly and self-metallization of porphyrin nanosheets. J Am Chem Soc 2007, 129: 2440. 10.1021/ja068250oView ArticleGoogle Scholar
- Yuasa M, Oyaizu K, Yamaguchi A, Kuwakado M: Micellar cobaltporphyrin nanorods in alcohols. J Am Chem Soc 2004, 126: 11128. 10.1021/ja0486216View ArticleGoogle Scholar
- Huang C, Li Y, Song Y, Li Y, Liu H, Zhu D: Ordered nanosphere alignment of porphyrin for the improvement of nonlinear optical properties. Adv Mater 2010, 22: 3532. 10.1002/adma.200904421View ArticleGoogle Scholar
- Wang Z, Medforth CJ, Shelnutt JA: Porphyrin nanotubes by ionic self-assembly. J Am Chem Soc 2004, 126: 15954. 10.1021/ja045068jView ArticleGoogle Scholar
- Wang Z, Medforth CJ, Shelnutt JA: Self-metallization of photocatalytic porphyrin nanotubes. J Am Chem Soc 2004, 126: 16720. 10.1021/ja044148kView ArticleGoogle Scholar
- Qiu Y, Chen P, Liu M: Evolution of various porphyrin nanostructures via an oil/aqueous medium: controlled self-assembly, further organization, and supramolecular chirality. J Am Chem Soc 2010, 132: 9644. 10.1021/ja1001967View ArticleGoogle Scholar
- McRae EG, Kasha M: Enhancement of phosphorescence ability upon aggregation of dye molecules. J Chem Phys 1958, 28: 721. 10.1063/1.1744225View ArticleGoogle Scholar
- Kano H, Kobayashi T: Time-resolved fluorescence and absorption spectroscopies of porphyrin J -aggregates. J Chem Phys 2002, 116: 184. 10.1063/1.1421073View ArticleGoogle Scholar
- Yao M, Iwamura Y, Inoue H, Yoshioka N: Amphiphilic meso-disubstituted porphyrins: synthesis and the effect of the hydrophilic group on absorption spectra at the air-water Interface. Langmuir 2005, 21: 595. 10.1021/la049045uView ArticleGoogle Scholar
- Zhang Y, Chen P, Liu M: A general method for constructing optically active supramolecular assemblies from intrinsically achiral water-insoluble free-base porphyrins. Chem Eur J 2008, 14: 1793. 10.1002/chem.200701333View ArticleGoogle Scholar
- Yao P, Qiu Y, Chen P, Ma Y, He S, Zheng JY, Liu M: Interfacial molecular assemblies of metalloporphyrins with two trans or one axial ligands. ChemPhysChem 2010, 11: 722. 10.1002/cphc.200900831View ArticleGoogle Scholar
- Zhang Y, Chen P, Ma Y, He S, Liu M: Acidification and assembly of porphyrin at an interface: counterion matching, selectivity, and supramolecular chirality. ACS Appl Mater Interfaces 2009, 1: 2036. 10.1021/am900399wView ArticleGoogle Scholar
- Barber DC, Freitag-Beeston RA, Whitten DG: Atropisomer-specific formation of premicellar porphyrin J-aggregates in aqueous surfactant solutions. J Phys Chem 1991, 95: 4074.View ArticleGoogle Scholar
- Steinbeck CA, Hedin N, Chmelka BF: Interactions of charged porphyrins with nonionic triblock copolymer hosts in aqueous solutions. Langmuir 2004, 20: 10399. 10.1021/la048435dView ArticleGoogle Scholar
- Mishra PP, Bhatnagar J, Datta A: The interplay of hydrophobic and electrostatic effects in the surfactant-induced aggregation/deaggregation of chlorin p6 . J Phys Chem B 2005, 109: 24225. 10.1021/jp052682oView ArticleGoogle Scholar
- Maiti NC, Mazumdar S, Periadamy N: J- and H-aggregate of porphyrin-surfactant complexes: time-resolved fluorescence and other spectroscopic studies. J Phys Chem B 1998, 102: 1528. 10.1021/jp9723372View ArticleGoogle Scholar
- Fleischer EB, Miller CK, Webb LE: Crystal and molecular structure of some metal tetraphenylporphyrins. J Am Chem Soc 1964, 86: 2342. 10.1021/ja01066a009View ArticleGoogle Scholar
- Yu W, Li Z, Wang T, Liu M: Aggregation and supramolecular chirality of achiral amphiphilic metalloporphyrins. J Colloid Interface Sci 2008, 326: 460. 10.1016/j.jcis.2008.06.049View ArticleGoogle Scholar
- Ganguli AK, Ganguly A, Vaidya S: Microemulsion-based synthesis of nanocrystalline materials. Chem Soc Rev 2010, 39: 474. 10.1039/b814613fView ArticleGoogle Scholar
- Pecher J, Mecking S: Nanoparticles of conjugated polymers. Chem Rev 2010, 110: 6260. 10.1021/cr100132yView ArticleGoogle Scholar
- Zhu M, Chen P, Liu M: Graphene oxide enwrapped Ag/AgX (X = Br, Cl) nanocomposite as a highly efficient visible-light plasmonic photocatalyst. ACS Nano 2011, 5: 4529. 10.1021/nn200088xView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.