Synthesis of Spherical Carbon Nitride-Based Polymer Composites by

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Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting Jalal Poostforooshan, Alireza Badiei, Mohammadreza Kolahdouz, and Alfred P. Weber ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b07909 • Publication Date (Web): 02 Aug 2016 Downloaded from http://pubs.acs.org on August 2, 2016

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ACS Applied Materials & Interfaces

Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting

Jalal Poostforooshan,†,‡ Alireza Badiei,†,* Mohammadreza Kolahdouz,§ and Alfred P. Weber‡,*

†

School of Chemistry, College of Science, University of Tehran, Tehran, Iran.

‡

Institute of Particle Technology, Technical University of Clausthal, Clausthal-Zellerfeld,

Germany. §

School of Electrical and Computer Engineering, University of Tehran, Tehran, Iran.

ACS Paragon Plus Environment


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ABSTRACT Here we report a novel, facile and sustainable approach for the preparation of spherical submicron carbon nitride-based polymer composites by continuous aerosol-photopolymerization process. In this regard, spherical mesoporous carbon nitride (SMCN) nanoparticles were initially prepared via a nanocasting approach using spray-drying synthesized spherical mesoporous silica (SMS) nanoparticles as hard templates. In addition to experimental characterization, the effect of porosity on the light absorption enhancement and consequently the generation rate of electronhole pairs inside the SMCN was simulated using a three-dimensional FDTD method. To produce the carbon nitride-based polymer composite, SMCN nanoparticles exhibit excellent performance in photopolymerization of butyl acrylate (PBuA) monomer in the presence of nmethyldiethanolamine (MDEA) as a co-initiator in a continuous aerosol-based process. In this one-pot synthesis, SMCN nanoparticles act not only as photoinitiators, but at the same time as fillers and templates. The average aerosol residence time in the photoreactor is about 90 s. The presented aerosol-photopolymerization process avoids the need for solvent and surfactant, operates at room temperature, and more importantly, is suitable to produce the spherical composite with hydrophobic polymers. Furthermore, we simulated the condition of SMCN nanoparticles during illumination in the gas phase process which can freely rotate. The results demonstrated that the hole (h+) density is almost equally distributed in the whole part of the SMCN nanoparticles due to their rotation, leading to efficient light harvesting and morehomogeneous photoreaction. The combination of the outstanding features of environmentally friendly SMCN, photopolymerization and aerosol processing might open new avenues, especially in green chemistry, to produce novel polymer composites with multifunctional properties.


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KEYWORDS: spherical mesoporous carbon nitride, carbon nitride-based polymer composite, aerosol-photopolymerization, efficient light harvesting, FDTD method.

1. INTRODUCTION Polymeric carbon nitride has attracted widespread attention due to its unique properties, including semiconductivity, biocompatibility, high chemical and thermal stability, easy processability into the desired shape, and abundance since it is only composed of carbon and nitrogen.1–4 Thereby, these advantages make carbon nitride a promising candidate for a wide range of applications. However, the efficiency of bulk carbon nitride is still restricted due to its small specific surface area. It is well recognized that the introduction of mesoporosity in carbon nitride is one of the most effective methods to increase the specific surface area.5,6 Among the various synthetic strategies, hard templating techniques, also known as ‘nanocasting’, using mesoporous silica materials as hard templates are extensively used for the preparation of mesoporous carbon nitride materials.7,8 Mesoporous carbon nitride materials are widely used in various applications including the aerobic oxidation of alcohols,9 photocatalytic hydrogen peroxide production10, hydrogen and carbon dioxide storage,11,12 direct hydroxylation of benzene,13 hydrogen evolution,14 and CO2 reduction.15 However, their application as photoinitiators in free radical polymerization is still at a very early stage, and only a few studies were reported.16,17 Like other semiconductor materials, combination of the outstanding features of carbon nitride and polymer is expected to positively improve the properties of the obtained composites. For example, Yan et al. demonstrated that gC3N4-poly(3-hexylthiophene) composites improved the hydrogen generation from water under



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visible light.18 Shi et al. revealed that sodium alginate/g-C3N4 nanocomposite films exhibited a significant enhance of 118.2 °C in the half thermal degradation temperature and their tensile strength was dramatically enhanced by 103% at 6.0 wt% loadings.19 Myllymaa et al. also reported that surface hydrophilicity of polypropylene was improved remarkably by the addition of silicon-doped carbon nitride coatings.20 Moreover, Wang and co-workers indicated that gC3N4 can significantly improve the mechanical, thermal and UV absorption properties of polymeric materials.21 It should be noted that the carbon nitride-based polymer composites are most often prepared in the liquid phase by direct solution blending of polymer and graphitic carbon nitride with low surface area. However, such process is time and cost consuming, for some polymers could not work and an appropriate solvent is always required. It is also hard to achieve a homogeneous dispersion due to the aggregation of fillers. Unfortunately, since most of the composite products are bulk materials with irregular morphology, further processing for practical application is severely limited. Furthermore, the previous synthetic methods are typically focused on the preparation of composites with hydrophilic polymers. These reports demonstrated that carbon nitride cannot be intimately combined with hydrophobic polymers by solution blending methods due to the weak van der Waals forces.19,22 Therefore, developing a facile and feasible approach to prepare carbon nitride-based hydrophobic polymer composite with spherical morphology is a great challenge for researchers in this field. In this work, spherical raspberry-like silica particles were initially synthesized by spray drying of nanocolloidal silica, using polyvinylpyrrolidone (PVP) as a template. After removal of the PVP by calcination, spherical mesoporous silica (SMS) nanoparticles were obtained. Then, spherical mesoporous carbon nitride (SMCN) nanoparticles with the very high surface area were prepared


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on the basis of nanocasting using SMS nanoparticles as hard templates. In addition to experimental characterization, the optical properties of resulting SMCN nanoparticles were analyzed with the three-dimensional finite difference time-domain (FDTD) method. Finally, we present for the first time a facile and sustainable approach to produce spherical submicron carbon nitride-based poly butyl acrylate (PBuA) composite in a continuous aerosol-photopolymerization process. It was observed that the SMCN nanoparticles exhibit excellent performance in the initiation of photopolymerization “in ﬂight”. Most importantly, SMCN nanoparticles act not only as polymerization photoinitiators, but at the same time as polymer fillers and templates. In contrast to conventional wet methods such as solution blending and emulsion polymerization, this gas-phase synthesis has many advantages, such as fast particle production, green method, simple fabrication steps, low fabrication cost and production of high purity materials with spherical morphology.23–25 Interestingly, the presented aerosol-photopolymerization process is suitable for hydrophobic polymers, avoids the need for surfactants and solvent and operates at room temperature. Also, the resulting polymer particles leaving the photoreactor were collected directly on the filter and no separation by downstream processes like centrifugation, washing and drying are required.

2. EXPERIMENTAL 2.1. Materials The polymer stabilizer polyvinylpyrrolidone (PVP) with an average molecular weight of 10,000, butyl acrylate (BuA, 99 wt %), n-methyldiethanolamine (MDEA, 99 wt %), ethylenediamine (EDA, 99 wt %), carbon tetrachloride (CCl4, 99.9 wt %) and hydrofluoric acid (HF, 48 wt %)



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were purchased from Sigma-Aldrich. Aqueous colloidal silica suspension of 20 nm nanoparticles (Köstrosol 2040AS, 40 wt %) was obtained from CWK Chemiewerk Bad Köstritz GmbH. All chemicals were used as received, without further purification.

2.2. Preparation of Spherical Mesoporous Silica (SMS) The SMS nanoparticles were synthesized by spray drying, conceptually similar to that previously described by Zeng and Weber.26 In a typical synthesis, 10 ml colloidal silica (20 nm) solution was diluted with 50 ml deionized water under stirring. Then, 3.7 g PVP was added to the aqueous colloidal silica solution and the mixture was stirred at room temperature until a clear solution was obtained. The solution was sonicated in an ultrasonic bath for 15 min. The resulting silica/PVP suspension was then employed in the aerosol setup consisting mainly of an aerosol nebulizer (Atomizer ATM 220, Topas), a tube furnace and a particle filter. PVP-containing silica aerosols were generated with the help of an atomizer operated by compressed air with a flow rate of 2.5 L/min. The spherical droplets were dried in a tube furnace with an inner diameter of 22 mm and a length of 65 cm corresponding to a mean residence time of approximately 6 s for the aerosol in the tube furnace reactor at 500 °C. The dry particles exiting the reactor were collected on a filter (Cellulose Nitrate Membrane Filter, pore size 1.2 µm, Sartorius) in a rig. This filter was maintained at a temperature of 80 °C in order to avoid water condensation. After powder collection, calcination was done in air at 600 °C for 6 h to remove remaining PVP from the asprepared SMS particles.


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2.3. Synthesis of Spherical Mesoporous Carbon Nitride (SMCN) The SMCN nanoparticles were prepared by using SMS nanoparticles as hard templates according to the literatures.27,28 A typical synthesis procedure was as follows: 1 g of aerosolsynthesized SMS nanoparticles was added to a mixture of ethylenediamine (2.7 g) and carbon tetrachloride (6 g). The resulting mixture was refluxed at 90 °C for 6 h to induce polymerization of the precursors, and was then placed in a drying oven for 12 h. Next, the obtained dark-brown solid was heated under a nitrogen flow of 80 mLmin-1, starting from room temperature to 600 °C at a heating rate of 3.0 °Cmin-1 and kept at these conditions for 5 h to carbonize the polymer. In order to remove the silica templates, the resulting black powders were stirred in 50 mL of HF for 24 h, followed by filtration, washing with water and ethanol several times. Finally, the powders were dried at 100 °C overnight.

2.4. Aerosol-Photopolymerization Process In a typical synthetic procedure, the SMCN nanoparticles, as photoinitiators and fillers, were dispersed in a mixture of butyl acrylate monomer solution and n-methyldiethanolamine (MDEA) as a co-initiator. After stirring for 2 h, the mixture solution was sprayed with nitrogen gas at a constant flow rate (1 L/min) in an atomizer to generate the aerosol droplets. These aerosol droplets were passed through the photoreactor, where the polymerization reaction was initiated upon UV irradiation (Scheme 1). The amount of SMCN and MDEA were 1 wt % and 10 vol % with respect to butyl acrylate monomer solution, respectively. The ﬂow-through photoreactor consists of an UV fluorescent lamp (Philips TL 20W/01 RS SLV) which is placed in the center and surrounded by the concentric aluminium oxide tube. The



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employed irradiation source emits a narrow band at 311 ± 2 nm (UVB) with a radiant exitance of 18 mW/cm2 at the envelope surface. The reactor tube length is 510 mm, and it is mounted in vertical alignment. The average aerosol residence time in the photoreactor which is operated at room temperature with a flow rate of 1 L/min is about 90 s.

Scheme 1. Schematic Diagram of Continuous Experimental Setup for AerosolPhotopolymerization Process

2.5. Samples Characterization The size distribution of the dried raspberry-like silica particles was measured with a scanning mobility particle sizer (SMPS, Model 5.403, Grimm). Transmission electron microscopy (TEM) was performed with a JEOL JEM2100 operated at 160 kV, while scanning electron microscopy (SEM) was carried out with a Zeiss DSM Gemini 982 operated at 5 kV. Small-angle X-ray scattering (SAXS) measurements were carried out with a modified Kratky camera. The incident


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beam was monochromated (copper anode, X-ray tube KFLCu2K, λ = 0.154 nm) and focused on the detection plane by means of a Goebel mirror. Wide-angle X-ray diffraction (XRD) was measured with a STOE Stadi P X-ray powder diffractometer with a germanium monochromated CuKα radiation (λ=1.54056 Å) and a Debye-Scherrer geometry under ambient temperature. Nitrogen adsorption–desorption isotherms were recorded with an ASAP 2020 from micromeritics. The Brunauer–Emmett–Teller (BET) method was utilized to calculate the specific surface areas. The pore size distributions were calculated from the adsorption branches of isotherms by using the Barrett–Joyner–Halenda (BJH) model. Thermogravimetric analysis (TGA) was carried out in the temperature range from ambient to 1000 °C in air or nitrogen atmospheres at a heating rate of 10 °C per min using a NETZSCH TG 209 F1 thermogravimetric analyzer. The XPS spectra were obtained using an ultrahigh vacuum (UHV) apparatus with a base pressure below 1 × 10-10 hPa. The sample was irradiated using the Al Kα line (photon energy of 1486.6 eV) of a non-monochromatic X-ray source (Omicron DAR 400). Electrons emitted were detected by a hemispherical analyzer (Omicron EA125) under an angle of 45° to the surface normal with a calculated resolution of 0.83 eV for detail spectra and 2.07 eV for survey spectra. All XPS experiments were carried out at room temperature. Raman spectrum was obtained using a SENTERRA spectrometer (Bruker) employing a semiconductor laser (λ = 532 nm) at room temperature. The resulting polymer particles which leaving the photoreactor were collected dry on a PTFE filter membrane with 500 nm average pore diameter and then FT-IR spectra were recorded using the FT-IR Bruker Tensor 27 instrument. Elemental analyses for C, H, N were performed on a Vario EL elemental analyzer.



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2.6. Simulation Method We have solved Maxwell’s wave equations to investigate the interaction of the SMCN nanoparticles with the incident light, using the finite-difference time-domain (FDTD) method. These nanoparticles were illuminated from up above and the grid size is refined as ∆s = 0.25 nm. The boundary conditions were set to perfectly matched layer (PML) in the propagation direction. The absorption of the SMCN nanoparticles (Pab) was calculated using the equation below:

= . ɛ ∮ ||

[1]

where w is the frequency of the incident light, E is the electric field, V is the volume of the absorber particle, and Im(ɛ) is the imaginary part of the permittivity of the particle.29–32 If every absorbed photon generates an electron-hole pair (the hole density that participated in photoreaction) becomes

= ℎ

[2]

where h is the charge of a hole, is the lamp irradiance, and is the spectral response of the SMCN.31,33


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3. RESULTS AND DISCUSSION 3.1. Experimental Characterization In the first experiment, spherical raspberry-like silica particles were produced by spray drying a silica suspension consisting of SiO2 nanoparticles with an average diameter of 20 nm and PVP as the pore template. During the evaporation of the solvent, a spontaneous self-organization of the silica nanoparticles took place in the droplet, resulting in spherical raspberry-like particles containing primary silica nanoparticles. Then, the spherical porous silica particles with welldefined pore structures were prepared by calcination of PVP under high temperature. The size distribution of aerosol raspberry-like silica particles was measured using a scanning mobility particle sizer (SMPS), and the results are provided in Figure 1. The total number concentration (TNC), geometric mean diameter (GMD), and geometric standard deviation (GSD) of the resulting particles were 1.77 × 107 particles cm-3, 176 nm, and 1.72, respectively. Furthermore, the thermogravimetric weight change of spray dried particles was recorded under an air atmosphere to indicate the thermal decomposition of PVP during calcination (Figure S1, Supporting Information). An initial slight weight loss of 3.5 wt % occurred below 200 °C due to the evaporation of the residual water contained in particles. A further significant mass loss was observed starting at about 300 °C due to the decomposition of the PVP contained in the particles. No considerable mass loss was observed above 600 °C, which proves the complete removal of PVP. The sample had a residual mass of about 75.2% after calcination at 600 °C.



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Figure 1. Typical size distribution of particles prepared by spray drying a silica suspension with PVP.

In the second experiment, the SMCN nanoparticles were prepared via a nanocasting approach using spray-drying synthesized SMSs as hard templates and EDA and carbon CCl4 as precursors. The structural analysis of the resulting materials was done by different powder X-ray diffraction techniques (SAXS and wide-angle XRD). Figure 2A shows the SAXS patterns of the parent porous silica template and resulting SMCN sample. The shape of the SAXS pattern of SMCN is almost similar to that of the parent silica template, which indicates that the structure of the SMCN is a faithful inverse replica of that of the template.28,34 However, the intensity of scattering peaks of the SMCN became a little weaker. Furthermore, the scattering peaks shifted to slightly higher q values, which implies that minor shrinkage occurred in the mesostructures due to the high pyrolysis temperature of 600 °C and removal of silica template by HF.34 The wide-angle XRD pattern of SMCN (Figure 2B) exhibits a single broad diffraction peak near 25.4°. This peak can be indexed to the (002) diffraction corresponding to an interlayer d-spacing


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of ~3.5 Å, which is almost the same as that obtained for nonporous carbon nitrides reported previously.27,35 This indicates that the wall structure of the SMCN sample is composed of carbon and nitrogen which are arranged in a turbostratic form with a uniform distribution of nitrogen atoms throughout the samples.27

Figure 2. (A) SAXS patterns of (a) SMS and (b) SMCN, and (B) the wide-angle XRD pattern of SMCN.

The textural parameters of SMS and SMCN samples were investigated by N2 adsorption– desorption measurements (Figure 3). Both materials exhibit typical type IV isotherm with a H1 hysteresis loop at the high relative pressure region according to the IUPAC classification and featured capillary condensation in the mesopores, which is typical for the well-ordered mesoporous materials. The calculated BET specific surface area and pore volume of SMSs are 138 m2/g and 0.31 cm3/g, respectively. It is very interesting to note that the specific surface area and the pore volume of SMCNs are much higher than that of the parent mesoporous silica templates. The BET specific surface area and total pore volume of the SMCN materials are 718 m2/g, and 1.22 cm3/g, respectively. The BJH adsorption pore size distributions of SMCN along with its parent mesoporous silica are also shown in the inset. SMS nanoparticles have narrow pore size distribution centered at ~8 nm (Figure 3, inset). It was observed that the pore size (~23 nm) of the SMCN is obviously larger than the primary silica particle diameter (20 nm), which was used as a template, ascribed to the shrinkage of filled carbon nitride polymeric materials



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inside the pores of SMS during the high temperature treatment of the mesoporous silica/carbon nitride composite or the partial filling of carbon nitride matrix in the SMS.24,34 Moreover, the pore size of SMCN material, which reflects the diameter of primary silica particle, is tunable and can be easily adjusted by the choice of the SMS template with an appropriate primary silica particle, as well as by changing the molar ratio of SMS to carbon and nitrogen precursor ratio.19,35

Figure 3. Nitrogen adsorption–desorption isotherms and pore size distributions (inset) of (a) SMS and (b) SMCN (open symbols: desorption, closed symbols: adsorption).

To further investigate the formation of the mesopores structure and the topology of the materials, the samples were observed by TEM. Figure 4a shows the TEM image of primary silica nanoparticles with average particle diameter of 20 nm which were used to produce SMSs. TEM images (Figure 4b–e) of the spherical SMS templates and the resulting SMCN samples show that the mesostructures are well replicated. Interestingly, the sphere-like morphology of SMCN similar to that of the parent SMS template was retained even after the removal of silica template


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by HF, suggesting a faithful replication process. A close view of one SMCN replica by TEM (Figure 4f) indicates that the resulting pore size is similar to that of the primary silica nanoparticles, which is in agreement with the results obtained by N2 adsorption–desorption. These results indicate that the pore size can be easily controlled by changing the size of the primary silica particles.

Figure 4. TEM images of (a) the silica nanoparticles, (b and c) the SMS nanoparticles and (d-f) the resulting SMCN nanoparticles.



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The successful replication and the formed mesostructures are also confirmed by SEM images of the SMS templates and resulting SMCNs. Figure 5a and c clearly exhibit that the spherical morphology is well replicated. A high-magnification SEM image of porous silica particles (Figure 5b) reveals that these particles, which are spherical raspberry-like in shape with rough appearance, are self-assembled from small primary silica nanoparticles. Moreover, the magnified SEM image of the SMCN replica obtained after the silica template removal (Figure 5d) clearly shows a porous structure with average pore size of ~20 nm. These results are consistent with the corresponding N2 adsorption–desorption and TEM results.

Figure 5. SEM images of (a and b) the spherical SMSs, and (c and d) the SMCN replicas at different magnifications.

To analyze the thermal stability of the SMCN nanoparticles, the thermogravimetric analysis (TGA) of samples under air and N2 atmospheres was carried out (Figure 6). TGA under air flow


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(Figure 6a) indicates that decomposition starts at 450 °C, with a significant mass loss of 85% between 500 and 700 °C, associated with the release of many small molecules, such as CO2, H2O, and N2, due to the reaction between carbon nitride and oxygen.34 Further heating of the remaining material exhibits that the residue after 700 °C was in the range of a few percent. In a N2 atmosphere (Figure 6b), the SMCN material was found to be stable at temperatures up to 600 °C. The sample had a residual mass of about 64.6% at 1000 °C, which indicates that a nitrogen atmosphere increases the thermal stability of the SMCN material.

Figure 6. The thermogravimetric curves of the SMCNs in (a) air and (b) nitrogen atmospheres.

The surface chemical compositions of SMCN was studied by XPS characterization. As illustrated in the survey spectrum (Figure 7a), there is a large signal for O while no peaks for other elements except C, N, O and F are observed. Oxygen atoms may come from the moisture, atmospheric O2 or CO2 adsorbed on the surface of SMCN.36 F atoms also come from the trace HF adsorbed on the surface of SMCN during the SMS template removal. The overall atomic carbon to nitrogen ratio of SMCN determined by XPS is found to be 5.06. To probe the details of the chemical bonding between the C and N atoms in the SMCN sample, the C1s and N1s peaks were deconvoluted. As shown in Figure 7b and c, the C1s peak was deconvoluted into four



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single peaks with binding energies of 290.6, 288.8, 287 and 285.4 eV, while the N1s peak can be deconvoluted into two peaks at binding energies of 399 and 401 eV. The sharp peak in the C1s spectrum centered at 285.4 eV with high intensity is assigned to pure graphitic sites in the amorphous carbon nitride matrix, whereas the peak at 287 eV is attributed to sp2 C atoms bonded to nitrogen atom inside the aromatic structure. In addition, the peaks at 288.8 and 290.6 eV suggest the presence of sp3 hybridized C atoms and sp2 C atoms in the aromatic ring attached to the NH2 group, respectively. In the N1s spectrum, the lowest energy contribution at 399 eV is attributed to N atoms sp2-bonded to C atoms, e.g. aromatic amines, while the highest energy contribution at 401 eV is assigned to N atoms trigonally coordinated with all the sp2 carbon atoms or bonded with the sp2 carbon atoms and hydrogen atoms. It can be suggested that in our sample nitrogen atoms were involved in two main surroundings either N atoms that participate in the pyridine rings which connected to two neighboring carbon atoms or trigonal N atoms that make coordinations to three neighboring atoms. The atomic ratio of the two corresponding species can be determined by calculating the area ratio of the peaks at 399 and 401 eV, respectively. The atomic ratio of 1.01 was achieved which indirectly shows that the amount of nitrogen atoms belonging to rings is approximately equal to the amount of nitrogen atoms bridging them. These assignments of XPS result are in close agreement with the binding energy values reported for nonporous and porous carbon nitride samples elsewhere.8,28,34,37–39 The nature of the carbon and nitrogen atoms in the SMCN was further characterized by FT-IR spectroscopy. The FT-IR spectrum of SMCN (Figure 7d) reveals the existence of the carbon nitride matrix and shows two strong peaks centered around 1250 cm-1 and 1583 cm-1, which are attributed to aromatic C–N stretching bonds and aromatic ring mode, respectively. In addition, the weaker band at 3430 cm-1 may be related to the stretching mode of N–H groups attached to the aromatic ring or O–H stretching vibrations of residual water.28 Combined results from XPS and FT-IR indicate that the nature of SMCN material is mainly composed of pyridine and benzene rings interconnected by nitrogen atoms, as already reported by a number of authors.8,34,40


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Figure 7. XPS spectra of the SMCN nanoparticles: (a) survey spectrum, (b) C 1s spectrum, and (c) N 1s spectrum; and (d) the FT-IR spectrum of the SMCN nanoparticles.

The Raman spectrum of SMCN is also shown in Figure 8. The spectrum exhibits two broad peaks centered at about 1345 and 1560 cm-1, corresponding to the D (disordered) and G (graphitic) modes, respectively, which are similar to the Raman modes of earlier synthesized solid carbon nitride.39 The value of the relative ID/IG ratio for SMCN is 1.01, suggesting that many sp2 hybridized carbon species are present in the graphitized pore walls.34,35,39



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Figure 8. The Raman spectrum of the SMCN sample.

The elemental composition of SMCN materials before and after carbonization, and after removal of parent silica templates was determined by CHN analysis (Table S1, Supporting Information). It was observed that 2.4% H and 12.9% other elements (probably Si, O, Cl or F) are present in the SMCNs after the silica removal. Hydrogen may come from either the moisture or ethanol adsorbed on the surface or NH group on the SMCN material (as evidenced by FT-IR spectroscopy). Elemental analysis also shows that our sample has a high nitrogen content (16.8 wt %) and the carbon-to-nitrogen atomic ratio of SMCN is about 4.04, which is in close agreement with the result obtained from XPS.

3.2. Finite-Difference Time-Domain Simulations To investigate the effect of the electric field by the introduction of mesoporosity in carbon nitride, the electric field distribution was simulated using a three-dimensional FDTD method. As shown in Figure 9A, three planes inside the SMCN nanoparticle were chosen to explore the interaction of the incident light with the sample: the middle cross-section of the upper


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hemisphere (Figure 9B), the centre plane of the nanoparticle (Figure 9C) and the middle crosssection of the lower hemisphere (Figure 9D). In this study, the electric field was obtained by averaging all values and normalizing the fields for all wavelengths of the UV lamp. According to the obtained electric fields of the three mentioned planes (Figure 9B-D), it was clearly confirmed that the field exists in every part of the SMCN nanoparticle, which it can be related to the porous structure of the SMCN nanoparticle. As depicted by FDTD simulations, significant incoming photons were confined inside the nanochannels of SMCN, leading to an enhanced field through the SMCN nanoparticle. As expressed in equation [1], this enhanced electric field can improve the light absorption and consequently increases the generation rate of electron-hole pairs inside the SMCN.29,41 Therefore, the probability of photoreaction can be improved effectively. To further investigate the effect of porosity on the field, the field distribution of a nonporous carbon nitride was also simulated by FDTD method (Figure S2, Supporting Information). From the comparison, it was observed that the electric field intensity inside the SMCN is stronger than that of the nonporous structure of carbon nitride for the all wavelengths of the UV lamp. Simulation results indicate a critical role of the porosity in the electric field enhancement inside the SMCN and improve its photocatalytic activity.



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Figure 9. Averaged and normalized electric field for the all wavelengths of the UV lamp at three cross-sections inside the SMCN nanoparticle using the FDTD method: (A) TEM image of SMCN nanoparticle, (B) middle cross-section of the upper hemisphere, (C) centre plane of the nanoparticle and (D) middle cross-section of the lower hemisphere.

3.3. Effect of Nanoparticle Rotation The effects of nanoparticle rotation on the hole density distribution as well as the photocatalytic performance of the SMCN nanoparticle are analyzed and discussed in this section. Figure 10


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demonstrates the hole density distribution inside the SMCN nanoparticle in two cases: nanoparticles with fixed orientations and in rotation. FDTD simulations of SMCN nanoparticle with fixed orientations show a considerable non-uniform hole density distribution inside the SMCN nanoparticle, as shown in Figure 10A. However, in the continuous gas-phase process, the nanoparticle can freely rotate within a range of orientation angles while passing through the photoreactor and during the illumination. When semiconductor nanoparticles rotate, the corresponding hole density distribution will not be the same as that obtained for these nanoparticles with fixed position. It is very interesting to note that with taking the nanoparticle rotation into consideration, the FDTD simulations unambiguously confirm that the hole density is almost equally distributed in the whole part of the SMCN nanoparticle, leading to efficient light harvesting (Figure 10B). From the viewpoint of practical applications, the photocatalytic activity of carbon nitride mainly relates to the oxidative ability of photogenerated holes in its valence band. Generally, the hole transfers from the valence band to the molecules adsorbed on the surface of carbon nitride, which consequently can oxidize the molecules into a final product. As a result, the photocatalytic efficiency was directly influenced by the quantity of photogenerated hole. According to the simulation results, it can be concluded that for SMCN nanoparticle with fixed position (Figure 10A), the efficiency of photoreaction is completely different in various parts of nanoparticle due to the non-uniform hole density distribution inside the SMCN nanoparticle, resulting in the considerable inhomogeneous product. In this case, the hole density distribution gradually decreases from top to bottom, revealing that more time and energy are required to create sufficient hole in the bottom of the nanoparticle. On the other hand, for the freely rotating SMCN nanoparticle in the continuous aerosol-based process, the equally distributed holes were generated simultaneously under UV irradiation which can lead directly to a more-homogeneous photoreaction in the whole part the SMCN nanoparticle. This enhanced optical property makes the obtained SMCN nanoparticle to be an optimal and promising candidate for various important applications in photocatalysis, since efficient photons might be harvested to run photoreactions. Consequently, the introduction of desired mesoporosity in the carbon nitride not only can increase the surface area for accommodating active sites and facilitate the diffusion of reactants and products molecules into the nanochannels of mesoporous, but also can result in



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efficient light harvesting. Accordingly, these superior properties of SMCN nanoparticle offer a vast range of potential applications for photocatalysis.

Figure 10. The hole density distribution of the SMCN nanoparticle: The SMCN nanoparticle is fixed to the space (A) and the nanoparticle is rotating (B). The rotation orientation is x-z plane and a complete rotation is considered.

3.4. Aerosol-Photopolymerization Finally, SMCN nanoparticles were used as photoinitiators, fillers and templates to produce spherical carbon nitride-based polymer composites in the continuous gas-phase process. It was observed that the SMCN nanoparticles could exhibit excellent performance in aerosolphotopolymerization of butyl acrylate (BuA). Figure 11a shows the low magnification SEM image of the resulting PBuA-SMCN composite particles produced in the presence of MDEA as a co-initiator, which indicates that they consist of a large amount of spherical polymer composites. The high magnification SEM image (Figure 11b) also shows that these particles have granular surface morphologies, which implies that their shapes differ from those of SMCN particles. The TEM image further confirms the formation of spherical PBuA-SMCN composite particles by aerosol-photopolymerization, as shown in Figure 11c. Furthermore, the production of PBuA-SMCN composite in the presence of MDEA using SMCN was analyzed by FT-IR (Figure 11d). A sharp intense peak at 1732 cm-1 appeared that can be


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assigned to the presence of ester carbonyl group stretching vibration, which exists in the PBuA. Carbon-carbon double bonds of acrylic monomers possess valence vibration between 1620 and 1680 cm-1. It is seen that this vibration is not observed in this spectrum, indicating polymerization has occurred and no unreacted BuA monomer residue remained on the SMCN particles after aerosol-photopolymerization. The broad band centered near 1585 cm-1 can be ascribed to C═N stretching bonds in the aromatic ring of SMCN nanoparticles. As control experiments, no polymer was formed in the dark or without SMCNs under our reaction condition. Based on these findings it was suggested that SMCN can serve as an effective photoinitiator for the photopolymerization of BuA monomer in the continuous aerosol-based process. Therefore, the presented aerosol-photopolymerization has great potential to produce polymer composites in a very simple, fast, and efficient “one-pot” procedure.

Figure 11. SEM (a and b), TEM (c) images and FT-IR spectrum (d) of PBuA-SMCN composites produced by aerosol-photopolymerization.



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Considering all above-discussed experimental and simulation results, the proposed mechanism of photopolymerization was illustrated in Scheme 2. Upon UV irradiation of semiconductor SMCN nanoparticles, positive holes (h+) in the valence band and simultaneously electrons (e-) in the conduction band will be generated. The valence-band hole is a good oxidant which can be reduced by hydrogen abstraction from the organic molecules such as amines and vinyl monomers.17,42 However, amines such as MDEA with the higher number of abstractable hydrogens, provide more favorable conditions.16 After amine oxidation, the corresponding radical cation was produced that can abstract hydrogen from another amine to generate an aminoalkyl radical which acts as photoinitiating species in the polymerization of acrylates. Although the role of the conduction-band electron is not clear, it was suggested that the electron can react with the produced tertiary ammonium ion to give a hydrogen radical and a neutral amine.16 Since the simulation results demonstrated that the hole density is equally distributed in the whole part of the SMCN nanoparticle, we speculate that the monomer can be polymerized homogeneously into the SMCN nanoparticle.

Scheme 2. Proposed Initiation Mechanism of the Photopolymerization Using SMCN in the Presence of the MDEA as Co-Initiator


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Highlights of the presented aerosol-photopolymerization process are the continuous, fast and simple setup with a flow-through photoreactor operates at room temperature. Furthermore, this method has potential to provide a new pathway to produce novel polymer composites with a variety of material combinations and multifunctional properties. It is worth noting that the production of polymer particles using photons as an energy source and employing environmentally friendly SMCN with their aforementioned excellent properties as a photocatalyst in an aerosol process, makes the presented aerosol-photopolymerization very interesting for green chemistry. Although the efficiency of this approach was limited by typical drawbacks such as low production rate and significant particle losses inside the polymerization photoreactor due to the diffusional processes,43–45 the purpose of the presented study was more focused on the investigate the optical properties of SMCN using FDTD method and synthetic feasibility of spherical submicron carbon nitride-based poly butyl acrylate (PBuA) composite in the aerosol-based method. However, the process optimization issues and more details on various properties of the resulting polymer composites will be addressed in our future work.

4. CONCLUSIONS In summary, SMCN nanoparticles were prepared via a nanocasting approach using aerosolgenerated SMS nanoparticles as hard templates. Experimental and simulation results confirm that the introduction of desired mesoporosity in the carbon nitride not only increases the surface area for accommodating active sites, but also improves the light absorption and consequently increases the generation rate of electron-hole pairs inside the SMCN. In addition, for the freely rotating SMCN nanoparticles in the gas-phase process, the hole (h+) density is almost equally



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distributed in the whole part of the SMCN nanoparticles, leading to efficient light harvesting and more-homogeneous photoreaction. Finally, we have demonstrated a facile and sustainable method for synthesis of spherical submicron carbon nitride-based polymer composites by the aerosol-photopolymerization

process.

In

this

one-pot

synthesis,

SMCN

nanoparticles can function as both the photoinitiators and fillers. As control experiments, when the experiments were carried out in the absence of SMCN or dark, the reactions failed to produce any polymer. Compared with conventional methods for preparation of carbon nitride-based polymer composites such as solution blending, the presented aerosol-photopolymerization process avoids the need for solvent and it is suitable for hydrophobic polymers and produces composites with spherical morphology. Thus, intensified interest can be foreseen in this approach, especially when high production rate of polymer particles is achieved. Furthermore, the various properties of the resulting polymer composites will be investigated in our future work.

■ ASSOCIATED CONTENT Supporting Information The Supporting Information is available free of charge on the ACS Publications website at DOI:XXX Additional data including Thermogravimetric analysis of particles prepared by spray drying (Figure S1); Elemental analysis results (Table S1); Electric field at three cross-sections inside the spherical nonporous carbon nitride nanoparticle (Figure S2).


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AUTHOR INFORMATION Corresponding Authors *Phone: +98 2161112614. Fax: +98 2166405141. E-mail: [email protected] *Phone: +49 5323722309. Fax: +49 5323722830. E-mail: [email protected]

ACKNOWLEDGMENTS We appreciate the technical assistance of Dr. Niels-Patrick Pook and Mrs. Karin Bode (Institute of Inorganic and Analytical Chemistry, TU Clausthal) for XRD and Raman measurements, respectively, Dr.-Ing. Gundula Helsch (Institute of Nonmetallic Materials, TU Clausthal) for UV–vis and FT-IR analyses, Dr. rer. nat. Sebastian Dahle (Institute of Energy Research and Physical Technologies, TU Clausthal) for XPS characterization, and Dr.-Ing. Xiaoai Guo (Institute of Mechanical Process Engineering and Mechanics, KIT) for SAXS measurements. The authors are also sincerely grateful to Jafar Poursafar (University of Tehran) for his contribution in the simulation parts. This work was supported by German Science Foundation (DFG) (Grant WE 2331/12-2) and University of Tehran.

REFERENCES (1)

Zhu, J.; Xiao, P.; Li, H.; Carabineiro, S. A. C. Graphitic Carbon Nitride: Synthesis, Properties, and Applications in Catalysis. ACS Appl. Mater. Interfaces 2014, 6, 16449– 16465.

(2)

Zhang, J.; Chen, Y.; Wang, X. Two-Dimensional Covalent Carbon Nitride Nanosheets: Synthesis, Functionalization, and Applications. Energy Environ. Sci. 2015, 8, 3092–3108.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(3)

Cui, F. Z.; Li, D. J. A Review of Investigations on Biocompatibility of Diamond-like Carbon and Carbon Nitride Films. Surf. Coatings Technol. 2000, 131, 481–487.

(4)

Ayán-Varela, M.; Villar-Rodil, S.; Paredes, J. I.; Munuera, J. M.; Pagán, A.; LozanoPérez, A. A.; Cenis, J. L.; Martínez-Alonso, A.; Tascón, J. M. D. Investigating the Dispersion Behavior in Solvents, Biocompatibility, and Use as Support for Highly Efficient Metal Catalysts of Exfoliated Graphitic Carbon Nitride. ACS Appl. Mater. Interfaces 2015, 7, 24032–24045.

(5)

Wang, X.; Maeda, K.; Chen, X.; Takanabe, K.; Domen, K.; Hou, Y.; Fu, X.; Antonietti, M. Polymer Semiconductors for Artificial Photosynthesis: Hydrogen Evolution by Mesoporous Graphitic Carbon Nitride with Visible Light. J. Am. Chem. Soc. 2009, 131, 1680–1681.

(6)

Tahir, M.; Cao, C.; Butt, F. K.; Idrees, F.; Mahmood, N.; Ali, Z.; Aslam, I.; Tanveer, M.; Rizwan, M.; Mahmood, T. Tubular graphitic-C3N4: A Prospective Material for Energy Storage and Green Photocatalysis. J. Mater. Chem. A 2013, 1, 13949–13955.

(7)

Wang, Y.; Wang, X.; Antonietti, M. Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry. Angew. Chemie Int. Ed. 2012, 51, 68–89.

(8)

Vinu, A. Two-Dimensional Hexagonally-Ordered Mesoporous Carbon Nitrides with Tunable Pore Diameter, Surface Area and Nitrogen Content. Adv. Funct. Mater. 2008, 18, 816–827.

(9)

Karimi, B.; Behzadnia, H.; Bostina, M.; Vali, H. A Nano-Fibrillated Mesoporous Carbon as an Effective Support for Palladium Nanoparticles in the Aerobic Oxidation of Alcohols “on Pure Water.” Chem. – A Eur. J. 2012, 18, 8634–8640.

(10)

Zhang, J.; Zhang, M.; Lin, L.; Wang, X. Sol Processing of Conjugated Carbon Nitride Powders for Thin-Film Fabrication. Angew. Chemie Int. Ed. 2015, 54, 6297–6301.

(11)

Zhang, M.; Wang, X. Two Dimensional Conjugated Polymers with Enhanced Optical Absorption and Charge Separation for Photocatalytic Hydrogen Evolution. Energy Environ. Sci. 2014, 7, 1902–1906.


Page 30 of 35

Page 31 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(12)

Zheng, D.; Pang, C.; Liu, Y.; Wang, X. Shell-Engineering of Hollow g-C3N4 Nanospheres via Copolymerization for Photocatalytic Hydrogen Evolution. Chem. Commun. 2015, 51, 9706–9709.

(13)

Shiravand, G.; Badiei, A.; Mohammadi Ziarani, G.; Jafarabadi, M.; Hamzehloo, M. Photocatalytic Synthesis of Phenol by Direct Hydroxylation of Benzene by a Modified Nanoporous Silica (LUS-1) under Sunlight. Chinese J. Catal. 2012, 33, 1347–1353.

(14)

Zhu, Y.-P.; Ren, T.-Z.; Yuan, Z.-Y. Mesoporous Phosphorus-Doped g-C3N4 Nanostructured Flowers with Superior Photocatalytic Hydrogen Evolution Performance. ACS Appl. Mater. Interfaces 2015, 7, 16850–16856.

(15)

Zheng, Y.; Lin, L.; Wang, B.; Wang, X. Graphitic Carbon Nitride Polymers toward Sustainable Photoredox Catalysis. Angew. Chemie Int. Ed. 2015, 54, 12868–12884.

(16)

Kiskan, B.; Zhang, J.; Wang, X.; Antonietti, M.; Yagci, Y. Mesoporous Graphitic Carbon Nitride as a Heterogeneous Visible Light Photoinitiator for Radical Polymerization. ACS Macro Lett. 2012, 1, 546–549.

(17)

Dadashi-Silab, S.; Tasdelen, M. A.; Kiskan, B.; Wang, X.; Antonietti, M.; Yagci, Y. Photochemically Mediated Atom Transfer Radical Polymerization Using Polymeric Semiconductor Mesoporous Graphitic Carbon Nitride. Macromol. Chem. Phys. 2014, 215, 675–681.

(18)

Yan, H.; Huang, Y. Polymer Composites of Carbon Nitride and poly(3-Hexylthiophene) to Achieve Enhanced Hydrogen Production from Water under Visible Light. Chem. Commun. 2011, 47, 4168–4170.

(19)

Shi, Y.; Jiang, S.; Zhou, K.; Bao, C.; Yu, B.; Qian, X.; Wang, B.; Hong, N.; Wen, P.; Gui, Z.; Hu, Y.; Yuen, R. K. K. Influence of g-C3N4 Nanosheets on Thermal Stability and Mechanical Properties of Biopolymer Electrolyte Nanocomposite Films: A Novel Investigation. ACS Appl. Mater. Interfaces 2014, 6, 429–437.

(20)

Myllymaa, K.; Myllymaa, S.; Korhonen, H.; Lammi, M. J.; Saarenpää, H.; Suvanto, M.; Pakkanen, T. A.; Tiitu, V.; Lappalainen, R. Improved Adherence and Spreading of Saos-2 Cells on Polypropylene Surfaces Achieved by Surface Texturing and Carbon Nitride



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Coating. J. Mater. Sci. Mater. Med. 2009, 20, 2337–2347. (21)

Shi, Y.; Gui, Z.; Yu, B.; Yuen, R. K. K.; Wang, B.; Hu, Y. Graphite-like Carbon Nitride and Functionalized Layered Double Hydroxide Filled Polypropylene-Grafted Maleic Anhydride Nanocomposites: Comparison in Flame Retardancy, and Thermal, Mechanical and UV-Shielding Properties. Compos. Part B Eng. 2015, 79, 277–284.

(22)

Zhang, Y.; Mao, F.; Yan, H.; Liu, K.; Cao, H.; Wu, J.; Xiao, D. A Polymer-MetalPolymer-Metal Heterostructure for Enhanced Photocatalytic Hydrogen Production. J. Mater. Chem. A 2015, 3, 109–115.

(23)

Boissiere, C.; Grosso, D.; Chaumonnot, A.; Nicole, L.; Sanchez, C. Aerosol Route to Functional Nanostructured Inorganic and Hybrid Porous Materials. Adv. Mater. 2011, 23, 599–623.

(24)

Chang, H.; Jang, H. D. Controlled Synthesis of Porous Particles via Aerosol Processing and Their Applications. Adv. Powder Technol. 2014, 25, 32–42.

(25)

Nandiyanto, A. B. D.; Okuyama, K. Progress in Developing Spray-Drying Methods for the Production of Controlled Morphology Particles: From the Nanometer to Submicrometer Size Ranges. Adv. Powder Technol. 2011, 22, 1–19.

(26)

Zeng, L.; Weber, A. P. Aerosol Synthesis of Nanoporous Silica Particles with Controlled Pore Size Distribution. J. Aerosol Sci. 2014, 76, 1–12.

(27)

Jin, X.; Balasubramanian, V. V.; Selvan, S. T.; Sawant, D. P.; Chari, M. A.; Lu, G. Q.; Vinu, A. Highly Ordered Mesoporous Carbon Nitride Nanoparticles with High Nitrogen Content: A Metal-Free Basic Catalyst. Angew. Chemie Int. Ed. 2009, 48, 7884–7887.

(28)

Talapaneni, S. N.; Anandan, S.; Mane, G. P.; Anand, C.; Dhawale, D. S.; Varghese, S.; Mano, A.; Mori, T.; Vinu, A. Facile Synthesis and Basic Catalytic Application of 3D Mesoporous Carbon Nitride with a Controllable Bimodal Distribution. J. Mater. Chem. 2012, 22, 9831–9840.

(29)

Zhao, W.; Guo, Y.; Wang, S.; He, H.; Sun, C.; Yang, S. A Novel Ternary Plasmonic Photocatalyst: Ultrathin g-C3N4 Nanosheet Hybrided by Ag/AgVO3 Nanoribbons with Enhanced Visible-Light Photocatalytic Performance. Appl. Catal. B Environ. 2015, 165,


Page 32 of 35

Page 33 of 35

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


335–343. (30)

Tian, C.; Li, J.; Ma, C.; Wang, P.; Sun, X.; Fang, J. An Ordered Mesoporous Ag Superstructure Synthesized via a Template Strategy for Surface-Enhanced Raman Spectroscopy. Nanoscale 2015, 7, 12318–12324.

(31)

Awal, M. A.; Ahmed, Z.; Talukder, M. A. An Efficient Plasmonic Photovoltaic Structure Using Silicon Strip-Loaded Geometry. J. Appl. Phys. 2015, 117, 63109.

(32)

Hippler, R.; Majumdar, A.; Bogdanowicz, R. D. Ellipsometric Study of Carbon Nitride Films Deposited by DC-Magnetron Sputtering. Photonics Lett. Pol. 2011, 3, 70–72.

(33)

Poursafar, J.; Kolahdouz, M.; Asl-Soleimani, E.; Golmohammadi, S. Ultrathin TandemPlasmonic Photovoltaic Structures for Synergistically Enhanced Light Absorption. RSC Adv. 2016, 6, 55354–55359.

(34)

Li, Q.; Yang, J.; Feng, D.; Wu, Z.; Wu, Q.; Park, S.; Ha, C.-S.; Zhao, D. Facile Synthesis of Porous Carbon Nitride Spheres with Hierarchical Three-Dimensional Mesostructures for CO2 Capture. Nano Res. 2010, 3, 632–642.

(35)

Xu, J.; Shen, K.; Xue, B.; Li, Y.-X.; Cao, Y. Synthesis of Three-Dimensional Mesostructured Graphitic Carbon Nitride Materials and Their Application as Heterogeneous Catalysts for Knoevenagel Condensation Reactions. Catal. Letters 2013, 143, 600–609.

(36)

Vinu, A.; Ariga, K.; Mori, T.; Nakanishi, T.; Hishita, S.; Golberg, D.; Bando, Y. Preparation and Characterization of Well-Ordered Hexagonal Mesoporous Carbon Nitride. Adv. Mater. 2005, 17, 1648–1652.

(37)

Zhao, Z.; Dai, Y.; Lin, J.; Wang, G. Highly-Ordered Mesoporous Carbon Nitride with Ultrahigh Surface Area and Pore Volume as a Superior Dehydrogenation Catalyst. Chem. Mater. 2014, 26, 3151–3161.

(38)

Qiu, Y.; Gao, L. Chemical Synthesis of Turbostratic Carbon Nitride, Containing C-N Crystallites, at Atmospheric Pressure. Chem. Commun. 2003, 2378–2379.

(39)

Liu, L.; Ma, D.; Zheng, H.; Li, X.; Cheng, M.; Bao, X. Synthesis and Characterization of



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Microporous Carbon Nitride. Microporous Mesoporous Mater. 2008, 110, 216–222. (40)

Vinu, A.; Srinivasu, P.; Sawant, D. P.; Mori, T.; Ariga, K.; Chang, J.-S.; Jhung, S.-H.; Balasubramanian, V. V.; Hwang, Y. K. Three-Dimensional Cage Type Mesoporous CNBased Hybrid Material with Very High Surface Area and Pore Volume. Chem. Mater. 2007, 19, 4367–4372.

(41)

Yang, T.-H.; Harn, Y.-W.; Pan, M.-Y.; Huang, L.-D.; Chen, M.-C.; Li, B.-Y.; Liu, P.-H.; Chen, P.-Y.; Lin, C.-C.; Wei, P.-K.; Chen, L.-J.; Wu, J.-M. Ultrahigh Density Plasmonic Hot Spots with Ultrahigh Electromagnetic Field for Improved Photocatalytic Activities. Appl. Catal. B Environ. 2016, 181, 612–624.

(42)

Qin, X.; Liu, S.; Lu, W.; Li, H.; Chang, G.; Zhang, Y.; Tian, J.; Luo, Y.; Asiri, A. M.; AlYoubi, A. O.; Sun, X. Submicrometre-Scale Polyaniline Colloidal Spheres: Photopolymerization Preparation Using Fluorescent Carbon Nitride Dots as a Photocatalyst. Catal. Sci. Technol. 2012, 2, 711–714.

(43)

Akgün, E.; Hubbuch, J.; Wörner, M. Perspectives of Aerosol-Photopolymerization: Nanoscale Polymer Particles. Chem. Eng. Sci. 2013, 101, 248–252.

(44)

Gao, Z.; Grulke, E.; Ray, A. Synthesis of Monodisperse Polymer Microspheres by Photopolymerization of Microdroplets. Colloid Polym. Sci. 2007, 285, 847–854.

(45)

Poostforooshan, J.; Rennecke, S.; Gensch, M.; Beuermann, S.; Brunotte, G.-P.; Ziegmann, G.; Weber, A. P. Aerosol Process for the In Situ Coating of Nanoparticles with a Polymer Shell. Aerosol Sci. Technol. 2014, 48, 1111–1122.


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Table of Contents Graphic 325x214mm (300 x 300 DPI)


Synthesis of Spherical Carbon Nitride-Based Polymer Composites by

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