Assembly of One-Dimensional Organic Luminescent Nanowires

J. Phys. Chem. C 2007, 111, 9177-9183

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Assembly of One-Dimensional Organic Luminescent Nanowires Based on Quinacridone Derivatives Jia Wang,† Yunfeng Zhao,† Junhu Zhang,† Jingying Zhang,† Bai Yang,† Yue Wang,*,† Dingke Zhang,‡ Han You,‡ and Dongge Ma‡ Key Laboratory for Supramolecular Structure and Materials of the Ministry of Education, College of Chemistry, Jilin UniVersity, Changchun 130012, People’s Republic of China, and State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China

Downloaded by SUNY UPSTATE MEDICAL UNIV on September 12, 2015 | http://pubs.acs.org Publication Date (Web): June 7, 2007 | doi: 10.1021/jp072488x

ReceiVed: March 29, 2007

The quinacridone derivatives N,N′-dialkyl-1,3,8,10-tetramethylquinacridone (CnTMQA, n ) 6, 10, 14) were used as building blocks to assemble luminescent nano- and microscale wires. It was demonstrated that CnTMQA with different lengths of alkyl chains display obviously different wire formation properties. C10TMQA and C14TMQA showed a stronger tendency to form 1-D nano- and microstructures compared with C6TMQA. The C10TMQA molecules could be employed to fabricate the wires with different diameters, which exhibited a size-dependent luminescence property. The emission spectrum of the C10TMQA wires with diameters of 200-500 nm shows a broad emission band at 560 nm and a shoulder at around 535 nm, while the emission spectrum of the C10TMQA wires with diameters of 2-3 µm reveals a narrower emission band at 563 nm. For the CnTMQA-based samples with different morphologies, the emission property change tendency agrees with that of the powder X-ray diffraction patterns of these samples.

Introduction Nanoscale materials such as nanowires, nanoparticles, and nanorods represent attractive building blocks for the fabrication of functional nanoscale devices.1 The quantum size effect of nanostructured materials could induce new optical, electronic, magnetic, and mechanical properties compared with those of common bulk materials.2 Especially, one-dimensional (1-D) nanostructures have attracted great attentions due to that 1-D nanowires or nanofibres with high length/diameter aspect ratio often display unusual physical and chemical properties.3 The 1-D assembly of organic functional molecules on various substrates offers a useful strategy for the construction of welldefined functional nanoscale materials that are potential candidates of active components in organic light emitting diodes (OLEDs), organic field-effect transistors (OFETs), and solar cells, etc.4-6 The optoelectronic materials and devices based on nanowires have been extensively investigated; however, most of the reported nanowires were comprised of inorganic substances3,7 or polymers.8 The use of small organic molecules in the construction of 1-D nanomaterials with well-defined structures remains a challenge.9,10 Recently, it was demonstrated that perylene bisimide derivatives could be employed as building blocks to assemble supramolecular 1-D nanostructures.11 To obtain desirable organic nanomaterials for optical and electronic applications, the design and synthesis of functional organic building blocks and self-assembly approaches of 1-D nanostructure should be focused on. Quinacridone (QA) and its derivatives are widely used organic pigments that display excellent fastness properties as well as * To whom correspondence should be addressed. Fax: +86-43185193421. E-mail: [email protected]. † Jilin University. ‡ Chinese Academy of Sciences.

pronounced photovoltaic and photoconductive activities.12-15 High photoluminescent efficiency in dilute solution combined with good electrochemical stability in the solid state has allowed the fabrication of high-performance OLEDs based on QA. A great deal of effort has been invested into optimization of QAbased devices in terms of efficiency and lifetime.16,17 Moreover, some studies on QA have been devoted to investigate the assembly and structure properties of this class of pigments. Mu¨llen and co-workers have carefully studied the phaseformation behavior and aggregation properties of some soluble quinacridones.18,19 Nakahara and co-workers have synthesized quinacridone derivatives with alkyl chains and used them in Langmuir-Blodgett films to control the orientation and packing of the chromophores.14,15 We have reported that highly ordered 2-D structures based on quinacridone derivatives could be obtained at highly oriented pyrolytic graphite (HOPG).20-22 Recently, we have carried out studies aimed at understanding how supramolecular organization in the solid state and assembly characteristic in solution phase affect the photoluminescent (PL) and electroluminescent (EL) properties of quinacridone derivatives.23 It is demonstrated that molecular packing properties have dramatic effect on the PL and EL properties of solid thin films, and it is possible to optimize the PL and EL properties of quinacridone derivatives through the regulation of molecular structure and a molecular 3-D packing feature. In this paper, we report the assembly of the 1-D luminescent nano-/microwires with controllable morphology based on quinacridone derivatives. Experimental Section Instrumentation. 1H NMR spectra were recorded on Bruker AVANVE 500 MHz spectrometer with tetramethylsilane as the internal standard. Mass spectra were measured on a GC/MS mass spectrometer. Photoluminescence spectra were collected on a Shimadzu RF-5301PC spectrophotometer. The fluorescence

10.1021/jp072488x CCC: $37.00 © 2007 American Chemical Society Published on Web 06/07/2007


9178 J. Phys. Chem. C, Vol. 111, No. 26, 2007 microscopy images were obtained on an Olympus BX51 fluorescence microscope. FESEM images were performed on a JSM 6700F field emission scanning electronic microscope. Preparation of Samples and Emission Spectra Measurement. The nanowires were prepared by injecting 100 µL of CnTMQA solution (1 × 10-3 M) in tetrahydrofuran (THF) into 5 mL of vigorously stirred water. The mixture solution was continually stirred for 3 min and sequentially was aged for 5 min at room temperature. The aged aqueous suspension of nanowires is transferred onto clean silicon or glass substrates and dried in air or vacuum for spectroscopic measurement. A 100 µL aliquot of CnTMQA solution in THF (1 × 10-4 M) was dropped onto a clean glass or silicon substrate. After natural evaporation of the THF solvent at room temperature under ambient atmosphere, microscale wires were generated on the substrate. The large-scale crystal samples were prepared by slowly diffusing methanol vapor into the chloroform solution of CnTMQA at room temperature for 3-5 days. The emission spectra of the nano- and microscale wires and large-scale crystals were recorded by the following procedure. The substrate with nano- or microscale wires was fixed on a holder and placed in the optical path of the exciting light source. The angle between the substrate plane and the exciting light was maintained at 45°. The large-scale crystal samples were stuck on the surface of the substrate by non-emissive silica grease, and the emission spectra were measured by the same procedure as nano- and microscale wires. A quartz cell was used to measure the solution emission spectra. The photoluminescent quantum yield of the nanowires was measured according to the reported approach.24 X-ray Crystallography. Single crystals suited for X-ray structural analysis were obtained by slow diffusion of methanol into chloroform solution of C6TMQA. Diffraction data were collected on a Rigaku R-AXIS RAPID diffractometer (Mo KR radiation, graphite monochromator) in the Ψ rotation scan mode. The structure determination was done with direct methods by using SHELXTL 5.01v and refinements with full-matrix leastsquares on F2. The positions of hydrogen atoms were calculated and refined isotropically. CCDC 626313 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge Crystallographic Data Centre). N,N′-Di(n-hexyl)-1,3,8,10-tetramethylquinacridone (C6TMQA). Under nitrogen, sodium hydride (2.0 g, 80 mmol) was added to a suspension of 1,3,8,10-tetramethylquinacridone (TMQA)23a (3.7 g, 10 mmol) in 100 mL of dry THF. The mixture was heated to reflux for 1 h, and then 1-bromohexane (9.9 g, 60 mmol) was added. The reaction mixture was continued to heat to reflux overnight. After distilling off excess 1-bromohexane and THF, methanol (50 mL) was added dropwise into the reaction mixture. The resulting suspension was stirred for 1 h. The generated orange precipitate was filtered and washed with petroleum ether. After drying in air, the crude C6TMQA was obtained in 90% yield, which was purified by column chromatography using silica gel with chloroform as eluent to yield 4.7 g of C6TMQA (85%). 1H NMR (CDCl3): δ 8.67 (s, 2H), 7.13 (s, 2H), 6.87 (s, 2H), 4.43-4.45 (t, 4H), 3.00 (s, 6H), 2.50 (s, 6H), 2.00 (m, 4H), 1.61-1.64 (m, 4H), 1.39-1.49 (m, 8H), 0.94-0.97 (t, 6H). MS: m/z 535.9 [M]+. Anal. Calcd (%) for C36H44N2O2 (536.75): C, 80.56; H, 8.26; N, 5.22. Found: C, 80.11; H, 8.29; N, 5.06. N,N′-Di(n-decyl)-1,3,8,10-tetramethylquinacridone (C10TMQA). TMQA (3.7 g, 10 mmol) reacted with 1-bromodecane (13.27 g, 60 mmol) according to the procedure described for the synthesis of C6TMQA to yield 5.19 g (80%) of C10TMQA.

Wang et al. SCHEME 1: Molecular Structures of Cn+1TMQA, n ) 5, 9, 13

1H

NMR (CDCl3): δ 8.72 (s, 2H), 7.16 (s, 2H), 6.89 (s, 2H), 4.47 (t, 4H), 3.01 (s, 6H), 2.51 (s, 6H), 2.01 (m, 4H), 1.59 (m, 4H), 1.29-1.48 (m, 24H), 0.87-0.90 (t, 6H). MS: m/z 647.9 [M]+. Anal. Calcd (%) for C44H60N2O2 (648.96): C, 81.43; H, 9.32; N, 4.23. Found: C, 81.14; H, 9.27; N, 4.26. N,N′-Di(n-tetradecyl)-1,3,8,10-tetramethylquinacridone (C14TMQA). TMQA (3.7 g, 10 mmol) reacted with 1-bromoteradecane (16.5 g, 60 mmol) according to the procedure described for the synthesis of C6TMQA to yield 5.71 g (75%) of C14TMQA. 1H NMR (CDCl3): δ 8.683 (s, 2H), 7.148 (s, 2H), 6.878 (s, 2H), 4.450 (t, 4H), 3.008 (s, 6H), 2.505 (s, 6H), 2.012 (m, 4H), 1.588-1.648 (m, 4H), 1.467-1.493 (m, 4H), 1.266-1.375 (m. 36H) 0.867-0.894 (t, 6H). MS: m/z 760.7 [M]+. Anal. Calcd (%) for C52H76N2O2 (761.17): C, 82.05; H, 10.06; N, 3.68. Found: C, 81.70; H, 10.12; N, 3.54. Results and Discussion The quinacridone derivatives N,N′-dialkyl-1,3,8,10-tetramethylquinacridone (CnTMQA, n ) 6, 10, 14) used in this study were synthesized according to the reported procedure23a and characterized by 1H NMR spectroscopy, mass spectra, and element analysis. CnTMQA molecules with different lengths of flexible side-chains (Scheme 1) were employed to fabricate organic nanowires by using reprecipitation approach,25 injecting an amount of CnTMQA solution in THF into a vigorously stirred water solution. The aged aqueous suspension of nanowires is transferred onto clean silicon or glass substrates for fluorescence microscopy and FESEM. The FESEM images (Figure 1) show that the 1-D CnTMQA wires, which were obtained by reprecipitation process, exhibit obviously different morphologies upon CnTMQA varying from C6TMQA to C14TMQA. Figure 1a illustrates the rodlike nanowires of C6TMQA, with width of 80 nm and length of 2 µm, respectively. Between the adjacent nanowires, although slight conglutination exists, it is not strong enough to destroy the monodispersity of the nanowires. The magnified image shows that the single C6TMQA nanowire has well-defined, smooth, and rodlike morphology (Figure 2). It is worth noting that after a long time of aging (24 h), some diamond-like microcrystals, which are similar to the C6TMQA crystals crystallized from chloroform solution, were generated on the substrate (Figure 1b). For C10TMQA, the ribbonlike wires with length of around 10 µm, width of 200 nm, and thickness of approximately several tens of nanometers, respectively, are prepared by reprecipitation approach (Figure 1c). The ribbonlike wires of C10TMQA clearly demonstrate smooth surface, parallel arrangement, and perfect monodispersity characteristics. The length and width of the wires of C14TMQA are in the ranges of 50-100 µm and 1-2 µm, respectively. Figure 1d shows the FESEM image of the C14TMQA wires, which display broader dimension distribution in width compared with the C10TMQA wires. It is worth noting that a few of the C14TMQA nanowires


Assembly of 1-D Organic Luminescent Nanowires

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Figure 1. FESEM images of CnTMQA 1-D nanocrystals prepared by reprecipitation process and transferred onto glass substrate: (a) C6TMQA; (b) C6TMQA, recorded after 24 h aging; (c) C10TMQA; (d) C14TMQA.

Figure 2. FESEM image of a rodlike nanocrystal of C6TMQA fabricated by reprecipitation approach.

with thinner and slightly curled shape are observed. In contrary to the C6TMQA wires, the morphologies of C10TMQA and C14TMQA wires exhibited obvious stability, and long-time aging (48 h) cannot lead to the aggregation of wires of C10TMQA and C14TMQA. Evaporation approach also was employed to fabricate CnTMQA molecules into luminescent wires. Following natural evaporation of the solutions of CnTMQA in THF (1 × 10-4

M) on the glass or silicon substrates at room temperature under ambient atmosphere, the fluorescent microscopy images were recorded (Figure 3). The experimental results demonstrated that the evaporation of C10TMQA or C14TMQA solution could lead to the formation of luminescent wires with high length/diameter aspect ratios (Figure 3b,c). The diameters of the wires are 2-3 µm for C10TMQA and 2-4 µm for C14TMQA, respectively. Solution evaporation process can lead to the formation of luminescent wires with bigger diameters compared with reprecipitation process. In contrast, the evaporation of C6TMQA solution only results in the generation of luminescent rodlike and diamond-like microcrystals (Figure 3a), suggesting that C10TMQA and C14TMQA molecules display stronger tendency to assemble into 1-D luminescent wires compared with C6TMQA molecules. It was demonstrated that the side-chain substitution had dramatic influence on the 1-D assembly properties of perylene diimide derivatives, which can be considered as the most close relative of the quinacridone derivatives.11b Therefore, these two classes of dyes may have a similar assembly property. Figure 4 presents the comparison of the emission spectra of C10TMQA in different states. The dilute C10TMQA solutions in THF and chloroform show strong green emission at 520 (in THF) and 535 nm (in chloroform), respectively, suggesting that C10TMQA has certain solvatochromism property in solution (Figure 4a,b). The large-scale C10TMQA crystals with approximate dimensions of 20 µm × 50 µm × 2000 µm display emission around 594 nm (Figure 4e). The C10TMQA wires with different diameters exhibit obviously different emission spectral


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Figure 3. Fluorescent microscopy images (upon excitation at 365 nm) of CnTMQA samples prepared by evaporating the solutions of CnTMQA in THF (1 × 10-4 M) on glass substrate: (a) C6TMQA; (b) C10TMQA; (c) C14TMQA.

Figure 4. PL spectra of C10TMQA samples: (a) in THF solution (6.2 × 10-5 M); (b) in chloroform solution (6.2 × 10-5 M); (c) nanowires with width of 200-500 nm prepared by reprecipitation approach; (d) microwires with width of 2-3 µm prepared by evaporation approach; (e) big crystals recrystallized from chloroform solution.

profiles (Figure 4c,d). The emission spectrum of the wires with diameter of 200-500 nm shows a broad emission spectrum with intensity maximum at 560 nm and a shoulder at around 535 nm, while the emission spectrum of the wires with diameter of 2-3 µm reveals a narrower emission band at 563 nm. The emission intensity maxima of the small-scale wires and largescale crystals display about 30 and 60 nm red shifts, respectively, compared with that of the dilute solution. This phenomenon should be attributed to the intermolecular π‚‚‚π stacking interactions.11b,23 The single-crystal structure and dynamic NMR studies for quinacridone derivatives reveal that there are strong intermolecular π‚‚‚π stacking interactions in the solid state and solution phase of the quinacridone derivitives.23 The photoluminescent quantum yield of the nanoscale wires is approximate 2.0%. The strong intermolecular interactions should be responsible for the low quantum yield.11b,23 The digital image of the C10TMQA dilute solution and fluorescence microscopy images of C10TMQA wires and

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Figure 5. Fluorescence images of C10TMQA samples (upon excitation at 365 nm): (a) sample in THF solution (6.2 × 10-5 M); (b) nanowires with width of 200-500 nm prepared by reprecipitation process; (c) microwires with width of 2-3 µm prepared by evaporation process; (d) crystals recrystallized from chloroform solution.

crystals are present in Figure 5, which document the different emission colors for C10TMQA in different states. A rational explanation for the above phenomena is that the wires with nano- and micrometer scales are the intermediates between the solution and big crystals of C10TMQA, and the emission properties of the wires tend to near the big crystals upon increasing the diameter of the wires. The solution, thin wires, and big crystals of C10TMQA represent the different aggregation states of C10TMQA molecules, respectively, i.e., monomer, mesoscale (nano- to micrometer), and bulk states, which should exhibit different emission properties.25 The above experimental results suggest that the C10TMQA wires really exhibit a sizedependent emission property.25b,26 The different emission properties observed for small-dimension wires (200-500 nm and 2-3 µm in diameters) and relatively big dimension crystals (20-50 µm in diameter) are most likely due to the different molecular packing structures, which have been supported by the powder X-ray characterization (as discussed below). To rule out the solvation possibility for different solid forms (nano- and microwires, and big crystals of C10TMQA), which may have effect on the emission property and induce the formation of exciplex emission, the following characterizations were performed. The solid samples dried in air were treated in a vacuum oven at 25 °C for 1 day, and then the emission spectra were measured. The experimental results show that vacuum treatment cannot led to the shift of emission spectra. Sequentially, the solid samples were placed in a closed chamber saturated with the vapor of THF or chloroform overnight and the emission spectra, which maintain their original profiles, were recorded. The dried samples were immersed in water for 2 h, and then the emission spectra were recorded immediately. No change was observed in the emission spectra (see Supporting Information). In addition, the element analysis demonstrated that no solvent molecules exist in the solid samples that were crystallized from THF or chloroform solution. Figure 6 presents the emission spectra recorded for C6TMQA in different states. The dilute solutions and relatively big crystals (approximate dimensions ) 0.5 mm × 1 mm × 1 mm) of C6TMQA exhibit relatively narrow emission bands at 520535 nm (520 nm in THF and 535 nm in chloroform) and 603



Figure 6. PL spectra of C6TMQA: (a) in THF solution (6.1 × 10-5 M); (b) in chloroform solution (6.1 × 10-5 M); (c) rodlike nanocrystals with width of 80-100 nm prepared by reprecipitation approach; (d) diamond-like microcrystals prepared by evaporation approach; (e) big crystals recrystallized from chloroform solution.

Figure 7. PL spectra of C14TMQA: (a) sample in THF solution (6.3 × 10-5 M); (b) sample in chloroform solution (6.3 × 10-5 M); (c) wires with width of 1-2 µm prepared by reprecipitation approach; (d) wires with width of 2-4 µm prepared by evaporation approach; (e) needlelike crystals recrystallized from chloroform solution.

nm, respectively. The emission of big crystals is obviously redshifted with respect to that of solution. This is due to the aggregation of C6TMQA molecules in the solid state. Although the emission spectra of the samples that were prepared by reprecipitation and solvent evaporation approaches display different profiles, they all pronouncedly overlap with the emission band of the big crystals. This phenomenon can be attributed to that there are similar small crystals in the samples prepared by reprecipitation and evaporation processes. The C14TMQA wires prepared by reprecipitation and evaporation approaches, respectively, and crystals grown from chloroform solution display similar emission characteristic (Figure 7). This phenomenon can be attributed to the three kinds of samples having similar morphology. It was demonstrated that tiny needlelike crystals were very easily generated by the vapor evaporation of C14TMQA solution in THF or chloroform (Figure 8). The solid samples of C6TMQA and C14TMQA also were treated in vacuum and solvents vapor and monitored with emission spectrometer, and the recorded emission spectra remain unchanged (see Supporting Information). The single crystals suited for X-ray structural analysis were obtained by slow diffusion of methanol vapor into chloroform solution of C6TMQA. The molecular and crystal packing

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Figure 8. Fluorescent microscopy image of long needlelike crystals of C14TMQA recrystallized from chloroform solution.

Figure 9. (a) ORTEP view drawing with thermal ellipsoid of C6TMQA (30% probability displacement ellipsoids); (b) H-bonding interactions in C6TMQA single crystal; (c) molecular packing structure of C6TMQA.

structures of C6TMQA are illustrated in Figure 9. The singlecrystal X-ray diffraction study reveals the planar geometry for the rigid π-cores of C6TMQA molecule. The C6TMQA molecular geometries are centrosymmetric and two alkyl chains adopt a regular all-trans conformation (Figure 9a). In crystal, each C6TMQA molecule is connected with four adjacent molecules through intermolecular C-H‚‚‚OdC (2.548 and 2.459 Å) hydrogen bonding interactions (Figure 9b). The molecular packing structure of C6TMQA crystal displays obviously anisotropic feature. Along the c-axis direction the C6TMQA molecules stack into infinite 1-D molecular columns (Figure 9c). The investigation of the crystal structure of C6TMQA suggests that CnTMQA molecules should have the tendency to aggregate into 1-D structure in nature. It is worth noting that no chloroform molecule is found in the crystal structure of C6TMQA. We have not obtained single crystals of C10TMQA and C14TMQA which are suitable for single-crystal X-ray diffraction studies. To understand the phase characteristics of the solid samples, powder X-ray diffraction analyses were performed.


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Figure 10. Powder XRD patterns of C6TMQA crystals with different morphologies: (a) nanoscale rods prepared by reprecipitation approach; (b) diamond-like microcrystals prepared by evaporation approach; (c) bulk diamond-like crystals recrystallized from chloroform solution.

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Figure 12. Powder XRD patterns of C14TMQA crystals prepared by different procedures: (a) microwires prepared by reprecipitation approach; (b) microwires prepared by evaporation approach; (c) long needlelike crystal recrystallized from chloroform solution.

(Figure 4). A rational explanation for this phenomenon is that a different crystalline phase should represent a different molecular packing structure in the solid state, which has dramatic influence on the emission property.11b The three kinds of C14TMQA wires, which were prepared by reprecipitation, evaporation, and crystallization approaches, respectively, exhibit identical X-ray patterns (Figure 12). The C14TMQA-based wires with similar morphology, emission property, and crystalline phase could be obtained by a different fabrication process. Conclusions

Figure 11. Powder XRD patterns of C10TMQA crystals with different morphologies: (a) nanoscale wires prepared by reprecipitation approach; (b) microscale wires prepared by evaporation approach; (c) bulk needlelike crystals recrystallized from chloroform solution.

Figure 10 illustrates the powder X-ray diffraction patterns of the C6TMQA samples with different morphologies. The macroscale (approximate dimensions ) 0.5 mm × 1 mm × 1 mm) and microscale (approximate dimensions ) 5 µm × 100 µm × 100 µm) crystals of C6TMQA display identical X-ray patterns, while the nanoscale rodlike sample (approximate dimensions ) 80 nm × 80 nm × 2000 nm) shows different a X-ray pattern compared with the macro- and microscale crystals. The results imply that the C6TMQA macro- and microscale crystals have a similar crystalline phase, which is different from that of the nanoscale rodlike crystals. The nanowires (approximate dimensions ) 20 nm × 200 nm × 10 µm) and microwires (approximate dimensions ) 0.5 µm × 3 µm × 1000 µm) of C10TMQA exhibit quite similar X-ray pattern, which is different from that of relatively macroscale needlelike crystals (approximate dimensions ) 20 µm × 50 µm × 2000 µm) of C10TMQA (Figure 11). Therefore, the C10TMQA-based nanoand microwires should have a similar crystalline phase that is different from that of macroscale needlelike crystals. Although it is impossible to make clear in detail the molecular packing structures based on the powder X-ray data, the molecular packing differences between the small-dimension wires and bigdimension crystals indeed exist. The samples with similar crystal phases display similar emission spectra, while the samples with different crystalline phases show different emission spectra

A series of quinacridone derivatives CnTMQA (n ) 6, 10, 14) have been employed to fabricate organic 1-D luminescent nano- and microwires based on the reprecipitation and evaporation approaches, respectively. Under the same fabrication condition, C6TMQA, C10TMQA, and C14TMQA display different assembly properties. C10TMQA and C14TMQA exhibit a stronger tendency to form a 1-D structure compared with C6TMQA. It was demonstrated that luminescent wires with uniform morphologies and controllable diameters could be easily prepared by C10TMQA molecules. The C10TMQA wires with different diameters, which were prepared by different fabrication processes, exhibit obviously different emission properties. Upon varying the states of C10TMQA from dilute solution to nano-/ microwires, and to bulk crystals, its luminescent properties show a successive alteration progress. It may be possible to control the luminescent properties of C10TMQA though varying the dimensions of C10TMQA-based wires. The powder X-ray diffraction studies revealed that the C10TMQA-based wires with similar emission properties have similar crystalline phases, while the solid samples with different emission properties possess different crystalline phases. Acknowledgment. This work was supported by the National Natural Science Foundation of China (Grant 50520130316), the Major State Basic Research Development Program (Grant 2002CB613401), the Program for Changjiang Scholars and Innovative Research Team in University (Grant IRT0422), and the 111 Project (Grant B06009). Supporting Information Available: Crystallographic information (CIF) of C6TMQA and emission spectra of solid samples. This material is available free of charge via the Internet at http://pubs.acs.org.



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