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1.
Fe–Ce–Al catalysts were synthesized by the co-precipitation method (labeled as Fe–Ce–Al–P), co-impregnation method (Fe–Ce–Al–I), and direct mixing method (Fe–Ce–Al–M), respectively, and used for effective removal of NO. The synthesized catalysts were characterized by many methods including N2 physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), high-resolution transmission electron microscopy (HR-TEM), and energy dispersive spectroscopy (EDS) mapping. The results show that the synthesis methods greatly influence the catalytic performance of catalysts. The Fe–Ce–Al–P catalyst prepared by the co-precipitation method yields the highest catalytic performance, while the Fe–Ce–Al–I and Fe–Ce–Al–M catalysts exhibit relatively low catalytic activity. The co-precipitation method can promote the accumulation and dispersion of more surface active species on the catalyst surface, and provide smaller particle size of active species and generate more uniform particle size distribution, while these characteristics can''t be obtained by the co-impregnation method and direct mixing method. Moreover, the co-precipitation method could produce the highest surface area and enhanced redox ability and surface acidity of the catalyst, which resulted from the high dispersion and uniform distribution of surface active species. These may be the key factors to the superior catalytic performance of the Fe–Ce–Al–P catalyst.Fe–Ce–Al catalysts were synthesized by the co-precipitation method (labeled as Fe–Ce–Al–P), co-impregnation method (Fe–Ce–Al–I), and direct mixing method (Fe–Ce–Al–M), respectively, and used for effective removal of NO. 相似文献
2.
Magdalena Jaboska Miren Agote Arn Andrew M. Beale Kinga Gra-Marek Grard Delahay Carolina Petitto Kateina Pacultov Regina Palkovits 《RSC advances》2019,9(7):3979
Cu–Al–Ox mixed metal oxides with intended molar ratios of Cu/Al = 85/15, 78/22, 75/25, 60/30, were prepared by thermal decomposition of precursors at 600 °C and tested for the decomposition of nitrous oxide (deN2O). Techniques such as XRD, ICP-MS, N2 physisorption, O2-TPD, H2-TPR, in situ FT-IR and XAFS were used to characterize the obtained materials. Physico-chemical characterization revealed the formation of mixed metal oxides characterized by different specific surface area and thus, different surface oxygen default sites. The O2-TPD results gained for Cu–Al–Ox mixed metal oxides conform closely to the catalytic reaction data. In situ FT-IR studies allowed detecting the form of Cu+⋯N2 complexes due to the adsorption of nitrogen, i.e. the product in the reaction between N2O and copper lattice oxygen. On the other hand, mostly nitrate species and NO were detected but those species were attributed to the residue from catalyst synthesis.Cu–Al–Ox mixed metal oxides with intended molar ratios of Cu/Al = 85/15, 78/22, 75/25, 60/30, were prepared by thermal decomposition of precursors at 600 °C and tested for the decomposition of nitrous oxide (deN2O). 相似文献
3.
Amir Hossein Khoshakhlagh Farideh Golbabaei Mojtaba Beygzadeh Francisco Carrasco-Marín Seyed Jamaleddin Shahtaheri 《RSC advances》2020,10(58):35582
The work presented here describes the synthesis of Cu–BDC MOF (BDC = 1,4-benzenedicarboxylate) based on oxidized activated carbon (microporous Cu–BDC@OAC composite) using an in situ method. The adsorbents (oxidized activated carbon (OAC), Cu–BDC and microporous Cu–BDC@OAC composite) were characterized by XRD, FTIR, SEM, EDS and BET techniques. Optimization of operating parameters affecting the efficiency of adsorption capacity, including adsorbent mass, flow rate, concentration, relative humidity and temperature, was carried out by central composite design (CCD) of the response surface methodology (RSM). An adsorbent mass of 60 mg, a flow rate of 90 mL min−1, the concentration of toluene (500 ppm), the relative humidity of 30% and a temperature of 26 °C were found to be the optimized process conditions. The maximum adsorption capacity for toluene onto Cu–BDC@OAC composite was 222.811 mg g−1, which increased by almost 12% and 50% compared with pure Cu–BDC and oxidized AC, respectively. The presence of micropores enhances the dynamic adsorption capacity of toluene. The regeneration of the composite was still up to 78% after three consecutive adsorption–desorption cycles. According to the obtained adsorbent parameters, microporous Cu–BDC@OAC was shown to be a promising adsorbent for the removal of volatile organic compounds.The work presented here describes the synthesis of Cu–BDC MOF (BDC = 1,4-benzenedicarboxylate) based on oxidized activated carbon (microporous Cu–BDC@OAC composite) using an in situ method. 相似文献
4.
Ni–Fe–P nanoparticles/graphene nanosheet (Ni–Fe–P/GNs) composites were successfully synthesized by a simple one-step hydrothermal method. Specifically, Ni2+ and Fe2+ were reduced by using milder sodium hypophosphite as a reducing agent in aqueous solution. SEM and TEM images show that a large number of Ni–Fe–P nanoscale microspheres are uniformly deposited on graphene nanosheets (GNs). At the thickness of 3.9 mm, the minimum reflection loss (RL) of Ni–Fe–P/GNs reaches −50.5 dB at 5.3 GHz. In addition, Ni–Fe–P/GNs exhibit a maximum absorption bandwidth of 5.0 GHz (13.0–18.0 GHz) at the thickness of 1.6 mm. The significant electromagnetic absorption characteristics of the Ni–Fe–P/GN composites can be attributed to the addition of magnetic particles to tune the dielectric properties of graphene to achieve good impedance matching. Therefore, Ni–Fe–P/GN is expected to be an attractive candidate for an electromagnetic wave absorber.Ni–Fe–P nanoparticle/graphene nanosheet composites synthesized by a one-step hydrothermal method have excellent performance in the field of electromagnetic wave absorption, with a minimum reflection loss of −50.5 dB and a maximum effective absorption bandwidth of 5 GHz. 相似文献
5.
Tong Li Yaoping Xie Xiaojiao Wang Qin Shen Jiabao Li Haibo Guo Jingxiang Xu Wenqing Liu 《RSC advances》2019,9(34):19620
Fe–1.0Cu (at%) and Fe–1.2Cu–2.2Mn alloys aged at 450 °C for 0.25 h, 1 h, 2 h, and 16 h after solution treatment at 900 °C for 2 h are investigated to reveal the role of the addition of Mn on the Cu precipitates in Fe–Cu based alloys. Density functional theory (DFT) total energy calculations on point defects and their influence on Cu precipitates are also performed to understand the nucleation and growth of Cu precipitates. Experiments show that addition of Mn can slightly increase the aging peak hardness by 10 HV; by using atom probe tomography (APT) and optical microscopy, we identify that the increase in hardness derives from both grain refinement and the increase of number density of precipitates. DFT calculations show that Mn increases the formation possibility of Frenkel pairs, i.e., atomic vacancy and self-interstitial atoms, and these two types of defects both serve as nucleation sites of Cu precipitates, resulting in the increase of the nucleation centers number density, which is consistent with our APT experiments on the very initial stage of aging. Moreover, calculated results show that Mn increases the density of atomic vacancies and promotes the evolution rate of Cu precipitates, which accounts for our APT experiments where precipitates in Fe–Cu–Mn grow more quickly than in Fe–Cu. Finally, we also discuss the relationship between Mn content in reactor pressure vessel steels and its irradiation damage effects.Fe–1.0Cu (at%) and Fe–1.2Cu–2.2Mn alloys aged at 450 °C for 0.25 h, 1 h, 2 h, and 16 h after solution treatment at 900 °C for 2 h are investigated to reveal the role of the addition of Mn on the Cu precipitates in Fe–Cu based alloys. 相似文献
6.
Hongling Dai Min Wang Wendong Luo Cheng Pan Fengping Hu Xiaoming Peng 《RSC advances》2019,9(57):33007
Hierarchical Cu–Al2O3/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu–Al2O3 frame (H–Cu–Al/BC) for the removal of ammonium nitrogen (NH4+-N) from aqueous solutions. The as-synthesized samples were characterized via XRD, SEM, BET and FTIR spectroscopy. The BET specific surface area of the synthesized H–Cu–Al/BC increased from 175.4 m2 g−1 to 302.3 m2 g−1 upon the incorporation of the Cu–Al oxide nanoparticles in the BC surface channels. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the adsorption kinetics of NH4+-N obeyed the pseudo-second-order kinetic model. The static maximum adsorption capacity of NH4+-N on H–Cu–Al/BC was 81.54 mg g−1, which was significantly higher than those of raw BC and H–Al/BC. In addition, the presence of K+, Na+, Ca2+, and Mg2+ ions had no significant impact on the NH4+-N adsorption, but the presence of Al3+ and humic acid (NOM) obviously affected and inhibited the NH4+-N adsorption. The thermodynamic analyses indicated that the adsorption process was endothermic and spontaneous in nature. H–Cu–Al/BC exhibited removal efficiency of more than 80% even after five consecutive cycles according to the recycle studies. These findings suggest that H–Cu–Al/BC can serve as a promising adsorbent for the removal of NH4+-N from aqueous solutions.Hierarchical Cu–Al2O3/biomass-activated carbon composites were successfully prepared by entrapping a biomass-activated carbon powder derived from green algae in the Cu–Al2O3 frame (H–Cu–Al/BC) for the removal of ammonium nitrogen (NH4+-N) from aqueous solutions. 相似文献
7.
A hollow Ni–Fe–B nanochain is successfully synthesized by a galvanic replacement method using a Fe–B nanocomposite and a NiCl2 solution as the template and additional reagent, respectively. Both the concentration of Ni and the morphology of the resulting Ni–Fe–B alloy are controlled by varying the duration of the replacement process during the synthesis. The Ni–Fe–B sample synthesized for 60 min (Ni–Fe–B-60) shows the best catalytic activity at 313 K, with a hydrogen production rate of 4320 mL min−1 gcat−1 and an activation energy for the NaBH4 hydrolysis reaction of 33.7 kJ mol−1. The good performance of Ni–Fe–B-60 towards the hydrolysis of NaBH4 can be ascribed to both hollow nanochain structural and electronic effects. Furthermore, the effects of temperature, catalyst amount, and concentration of NaOH and NaBH4 on the hydrolysis process are systematically studied, and an overall kinetic rate equation is obtained. The hollow Ni–Fe–B nanochain catalyst also shows good reusability characteristics and maintained its initial activity after 5 consecutive cycles.A hollow Ni–Fe–B nanochain is successfully synthesized by a galvanic replacement method using a Fe–B nanocomposite and a NiCl2 solution as the template and additional reagent, respectively. 相似文献
8.
Abhishek T. Sose Hannah D. Cornell Bradley J. Gibbons Ashley A. Burris Amanda J. Morris Sanket A. Deshmukh 《RSC advances》2021,11(28):17064
Solvent plays a key role in biological functions, catalysis, and drug delivery. Metal–organic frameworks (MOFs) due to their tunable functionalities, porosities and surface areas have been recently used as drug delivery vehicles. To investigate the effect of solvent on drug adsorption in MOFs, we have performed integrated computational and experimental studies in selected biocompatible MOFs, specifically, UiO-AZB, HKUST-1 (or CuBTC) and NH2-MIL-53(Al). The adsorption of three drugs, namely, 5-fluorouracil (5-FU), ibuprofen (IBU), and hydroxyurea (HU) were performed in the presence and absence of the ethanol. Our computational predictions, at 1 atmospheric pressure, showed a reasonable agreement with experimental studies performed in the presence of ethanol. We find that in the presence of ethanol the drug molecules were adsorbed at the interface of solvent and MOFs. Moreover, the computationally calculated adsorption isotherms suggested that the drug adsorption was driven by electrostatic interactions at lower pressures (<10−4 Pa). Our computational predictions in the absence of ethanol were higher compared to those in the presence of ethanol. The MOF–adsorbate interaction (UHA) energy decreased with decrease in the size of a drug molecule in all three MOFs at all simulated pressures. At high pressure the interaction energy increases with increase in the MOFs pore size as the number of molecules adsorbed increases. Thus, our research shows the important role played by solvent in drug adsorption and suggests that it is critical to consider solvent while performing computational studies.Solvent plays a key role in drug loading in metal–organic frameworks. 相似文献
9.
The Ca–Al and Ca–Al–X (X = F−, Cl− and Br−) catalysts were prepared via thermal decomposition of Ca–Al layered double hydroxides (LDHs), and tested for methanolysis of propylene carbonate (PC) to produce dimethyl carbonate (DMC). The catalytic performance of these catalysts increased in the order of Ca–Al–Br− < Ca–Al < Ca–Al–Cl− < Ca–Al–F−, which was consistent with the strong basicity of these materials. The recyclability test results showed that the addition of Al and halogens (F−, Cl− and Br−) not only stabilized the CaO but also improved the recyclability of the catalysts. Particularly, the Ca–Al–F− catalyst exerted the highest stability after 10 recycles. These catalysts have an important value for the exploitation of DMC synthesis by transesterification of PC with methanol.The CA-F− catalyst modified with Al3+ and F− was highly active and recyclable for dimethyl carbonate synthesis. 相似文献
10.
Min Li Jianxing Shen Chuanbing Cheng Tailin Wang Yan Shen Shuai Wang Pan Chen 《RSC advances》2019,9(16):9022
The gas sensors have been widely used in various fields, to protect the safety of life and property. A novel heterostructure of Fe–O–Ti nanoparticles is fabricated by hydrothermal and wet chemical deposition methods. The Fe–O–Ti nanoparticles with a large number of pores possess high surface area, which is in favour of high-performance gas sensors. Compared with pure Fe2O3 and TiO2, the Fe–O–Ti composite exhibits obviously enhanced sensing characteristics, such as faster response–recovery time (Tres = 6 s, Trec = 48 s), higher sensing response (response = 35.6) and better selectivity. The results show that the special morphology and large specific surface area of mulberry-like Fe–O–Ti heterostructures provided a large contact area for gas reactions.The gas sensors have been widely used in various fields, to protect the safety of life and property. 相似文献
11.
Lin Gu Yunyun Dong Yan Zhang Bo Wang Qing Yuan Hongmei Du Jinsheng Zhao 《RSC advances》2020,10(15):8709
In this study, a nitrogen-containing ligand supramolecule named PPYTZ was successfully synthesized using 2,6-pyridinedicarboxylic acid chloride and 3,5-diamino-1,2,4-triazole in order to carry out oxygen reduction reaction (ORR). Such a polymer provides abundant coordination sites for iron ions, and the PPYTZ–Fe/C composite catalyst was formed with the PPYTZ–Fe complex loading on the surface of Vulcan XC-72 carbon. The physical characteristics and ORR performance of the composite catalysts were characterized systematically via various relevant techniques, and their catalytic activity and reaction mechanism were evaluated and compared. The results showed that the catalytic activities and the reaction mechanism of ORR were highly dependent on the formation of an Fe–N unit. Accordingly, the PPYTZ–Fe/C catalyst containing Fe–N active sites exhibited high ORR catalytic activity (an onset potential of +0.86 V vs. RHE) in 0.1 M KOH. Such an Fe–N catalyst can accelerate the adsorption of O2 and increase the limiting current density (from 2.49 mA cm−2 to 4.98 mA cm−2), optimizing the ORR catalytic process from a two-electron process to a four-electron process (an n value of 3.8).The PPYTZ–Fe/C catalyst containing Fe–N active sites exhibited high ORR catalytic activity and stability in alkaline media with a four-electron pathway progress. 相似文献
12.
Alloyed structures of quantum dot light-harvesting materials favor the suppression of unwanted charge recombination as well as acceleration of the charge extraction and therefore the improvement of photovoltaic performance of the resulting solar cell devices. Herein, the advantages of Zn–Cu–In–S (ZCIS) alloy QD serving as light-harvesting sensitizer materials in the construction of quantum dot-sensitized solar cells (QDSCs) were compared with core/shell structured CIS/ZnS, as well as pristine CIS QDs. The built QDSCs with alloyed Zn–Cu–In–S QDs as photosensitizer achieved an average power conversion efficiency (PCE) of 8.47% (Voc = 0.613 V, Jsc = 22.62 mA cm−2, FF = 0.610) under AM 1.5G one sun irradiation, which was enhanced by 21%, and 82% in comparison to those of CIS/ZnS, and CIS based solar cells, respectively. In comparison to cell device assembled by the plain CIS and core/shell structured CIS/ZnS, the enhanced photovoltaic performance in ZCIS QDSCs is mainly ascribed to the faster photon generated electron injection rate from QD into TiO2 substrate, and the effective restraint of charge recombination, as confirmed by incident photon-to-current conversion efficiency (IPCE), open-circuit voltage decay (OCVD), as well as electrochemical impedance spectroscopy (EIS) measurements.Benefiting from the accelerative electron injection and retarded charge recombination, Zn–Cu–In–S alloy QD based QDSC achieved a PCE of 8.55%, which is 21%, and 82% higher than those of CIS/ZnS, and pristine CIS QDs based solar cells, respectively. 相似文献
13.
Yuansi Hu 《RSC advances》2021,11(47):29620
In this study, a microwave (MW) radiation enhanced Fe–C/PS system was used to treat refractory organic matter in biologically-treated landfill leachate. The effects of important influencing factors on the refractory organic matter in biologically treated landfill leachate were explored, and the main reactive oxygen species produced in the system were verified. The mechanism by which humus was degraded was investigated by analyzing effectiveness of organics removal in different systems, and comparative analysis was conducted on the Fe–C materials before and after the reaction. The results showed that degradation capacity and reaction rate of the system could be improved with an increase in the Fe–C/PS dosage and MW power, while initial acidic conditions were also conducive to the degradation of organic matter. Under the conditions of an Fe–C of 1 g L−1, PS dosage of 30 mM, MW power of 240 W, and reaction time of 10 min, the UV254, TOC, and CN removal efficiencies were 51.48%, 94.56%, and 51.59%, respectively. In the MW/Fe–C/PS system, a large amount of and a small amount of ˙OH were generated by the thermal activation of PS to remove organic matter. The removal efficiency of organic matter could be further improved via the homogeneous catalytic oxidation and heterogeneous adsorption catalytic oxidation of Fe–C materials. In addition, the MW/Fe–C/PS system was effective for removing refractory organic matter from the leachates from four typical treatment systems: DTRO, SAARB, MBR, and NF. The MW/Fe–C/PS system has the potential to be widely applied for the treatment of landfill leachate.A microwave radiation enhanced Fe-C/PS system was used to treat biologically-treated landfill leachate. This process showed wide applicability in treatment of four types of leachates and has a promising potential in landfill leachate treatment. 相似文献
14.
Oleksandr Stroyuk Oleksandra Raievska Dmytro Solonenko Christian Kupfer Andres Osvet Miroslaw Batentschuk Christoph J. Brabec Dietrich R. T. Zahn 《RSC advances》2021,11(34):21145
The effect of spontaneous alloying of non-stoichiometric aqueous Ag–In–S (AIS) and Cu–In–S (CIS) quantum dots (QDs) stabilized by surface glutathione (GSH) complexes was observed spectroscopically due to the phenomenon of band bowing typical for the solid–solution Cu(Ag)–In–S (CAIS) QDs. The alloying was found to occur even at room temperature and can be accelerated by a thermal treatment of colloidal mixtures at around 90 °C with no appreciable differences in the average size observed between alloyed and original individual QDs. An equilibrium between QDs and molecular and clustered metal–GSH complexes, which can serve as “building material” for the new mixed CAIS QDs, during the spontaneous alloying is assumed to be responsible for this behavior of GSH-capped ternary QDs. The alloying effect is expected to be of a general character for different In-based ternary chalcogenides.The effect of spontaneous alloying of aqueous glutathione-capped Ag–In–S and Cu–In–S quantum dots (QDs) into quaternary Cu(Ag)–In–S QDs is reported. 相似文献
15.
This study reveals a unique Cu–Cu2O@TiO2 heterojunction photocatalyst obtained with metal–organic framework as the precursor, which can be utilized in dye photodegradation under visible light irradiation. The composition, structure, morphology, porosity, optical properties and photocatalytic performance of the obtained catalysts were all investigated in detail. The Cu–Cu2O@TiO2 nanocomposite is composed of lamellar Cu–Cu2O microspheres embedded by numerous TiO2 nanoparticles. Methylene blue, methyl orange and 4-nitrophenol were used as model pollutants to evaluate the photocatalytic activity of the Cu–Cu2O@TiO2 nanocomposite for dye degradation under visible light irradiation. Nearly 95% decolourisation efficiency of Methylene blue was achieved by the Cu–Cu2O@TiO2 photocatalyst within 3 h, which is much higher than that of TiO2 or Cu2O catalysts. The excellent photocatalytic activity was primarily attributed to the unique MOF-based mesoporous structure, the enlarged photo-adsorption range and the efficient separation of the charge carriers in the Cu–Cu2O@TiO2 heterojunction.Cu–Cu2O@TiO2 heterojunction photocatalyst derived from a metal–organic framework shows high photocatalytic activity for dye degradation under visible light irradiation. 相似文献
16.
Peroxidases are enzymes that use hydrogen peroxide to oxidize substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ATBS). In this study, we showed that copper–tripeptide complexes (“cuzymes”) also exhibited peroxidase-like activities. Different cuzymes could be formed by using various tripeptide ligands, such as GGG, GGH or HGG. However, the peroxidase-like activity of cuzymes depends on the sequence of the tripeptide (Cu–GGG > Cu–HGG > Cu–GGH). When ABTS was used as the substrate, the activity of Cu–GGG was 326 ± 1.5 U mg−1 which was 2.5 times higher than that of horseradish peroxidase (HRP). Copper–tripeptide complexes were also used to degrade trypan blue dye. By using 0.2 mM Cu–GGG and 0.2% H2O2, 200 μM trypan blue could be degraded in 15 min at 50 °C. The degradation reaction followed second-order kinetics; the reaction rate was proportional to both H2O2 concentration and the copper–tripeptide concentration, but it was independent of the trypan blue concentration. Because copper–tripeptides catalyzed the oxidation reactions involving H2O2 effectively, they may have potential applications in biochemical assays and environmental remediation.Copper–tripeptide complexs (cuzyme) exhibited peroxidase-like activities that use hydrogen peroxide to oxidize substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ATBS) and trypan blue dye. 相似文献
17.
Metal–N–C-based catalysts prepared by pyrolysis are frequently used in the oxygen reduction reaction (ORR). Zeolitic imidazolate frameworks (ZIFs), a type of metal organic framework (MOF), are selected as precursors due to their special structure and proper pore sizes. A series of Fe–N–C catalysts with different concentrations of 2-methylimidazole were prepared with a simple solvothermal-pyrolysis method, and the transformation productivity, morphology and ORR activity were investigated. It was found that the Fe–N–C catalyst with a 2-methylimidazole concentration of 0.53 mol L−1 had the best performance. In 0.1 M KOH solution, the half-wave potential was 0.852 V (vs. RHE), with the highest electrochemically active surface area (ECSA) of 94.1 cm2, and the ORR reaction was dominated by a 4-electron process. The current only decreased by 10.5% after 50 000 s of chronoamperometry (CA), while the half-wave potential only decreased 20 mV in 3 M methanol. Additionally, this catalyst cannot be poisoned by Cl− and SO32− ions in the ORR process. Finally, some typical ions including SCN−, Fe(CN)63− and Fe(CN)64− were used to inhibit the active sites, and it was determined that Fe(ii) is the real active species. The series of synthesis and testing experiments has significance in guiding optimization of the synthesis conditions and analysis of the mechanism of active sites in Fe–N–C materials.Metal–N–C-based catalysts prepared by pyrolysis are frequently used in the oxygen reduction reaction (ORR). 相似文献
18.
Shenjie Li Tianyong Zha Xiaoyu Gong Qi Hu Minghui Yu Jinyu Wu Ruolan Li Jiaming Wang Yanyan Chen 《RSC advances》2020,10(41):24425
We present a facile route for the synthesis of water-soluble Cu–Cd–Zn–S/ZnS core/shell quantum dots (QDs) by simple pH regulation. The PL spectra of Cu–Cd–Zn–S/ZnS core/shell quantum dots can cover the whole visible light region in the case of only two ratios of Cu/Cd/Zn. The emission wavelength of Cu–Cd–Zn–S/ZnS QDs can be conveniently tuned from 474 to 515 and 548 to 629 nm by adjusting the pH value when the ratios of Cu/Cd/Zn are fixed at 1 : 5 : 80 and 1 : 5 : 10, respectively. It is worth noting that under the condition of a constant Cu/Cd/Zn ratio, the UV-vis absorption spectra do not change with the fluorescence spectra, indicating that the band gap of QDs remains unchanged during the change of pH value. The photoluminescence (PL) quantum yield of the as-prepared QDs with yellow emission is up to 76%. The QDs also show excellent chemical stability after the deposition of the ZnS shell. Luminescent and flexible films are fabricated by combining Cu–Cd–Zn–S QDs with polyvinyl alcohol (PVA). The QD/PVA flexible hybrid films are successfully applied on top of a conventional blue InGaN chip for remote-type warm-white LEDs. As-fabricated warm-white LEDs exhibit a higher color rendering index (CRI) of about 89.2 and a correlated color temperature (CCT) of 4308 K.We present a facile route for the synthesis of water-soluble Cu–Cd–Zn–S/ZnS core/shell quantum dots (QDs) by simple pH regulation. 相似文献
19.
The development of low-cost, efficient and stable electrocatalysts for the oxygen reduction reaction (ORR) is desirable but remains a great challenge. We report a convenient and efficient synthesis approach of highly dispersed Fe–Nx catalysts for ORR. Typically, Fe–Zn-ZIF (zeolitic imidazolate frameworks) nanocrystals cast as precursor and graphene as supports, highly dispersed Fe–Nx species were fabricated with PVP (polyvinyl pyrrolidone) as surfactant via pyrolysis. With the help of graphene and surfactant, the agglomeration of iron particles has been avoided during pyrolysis, and the size and morphology of ZIF particles intercalating into the graphene layers can be regulated precisely as well. The amount of Fe–Nx active sites in C-rGO-ZIF catalyst arrived 4.29%, which is obviously higher than most monodispersed non-precious metal catalysts reported. The obtained C-rGO-ZIF catalyst exhibits a high onset potential of 0.89 V and a half-wave potential of 0.77 V, which is only 30 mV away from Pt/C in acidic media. The active sites of the catalyst was characterized and found to be the highly dispersed Fe–Nx species, large and accessible specific surface area of graphene and abundant active nitrogen atoms. When the C-rGO-ZIF catalyst was applied in the cathode of fuel cell, the power density can reach up to 301 mW cm−2, which highlights a practical application potential on small power supplies.A tunable and convenient synthesis approach of highly dispersed Fe–Nx catalysts for ORR in acidic media was reported. 相似文献
20.
In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol. Mg–Al–La composite oxide was synthesized from the β-cyclodextrin (β-CD) intercalation modification of Mg–Al–La layered double hydroxides. The structure of the catalyst was characterized via XRD, BET and EDS. The results showed that the interlayer space of the catalyst was increased due to β-CD intercalation modification. The IL/CD–Mg–Al–La catalyst exhibited significant catalytic activity and regeneration performance in transesterification due to large interlayer space and strongly alkaline ionic liquid. The yield of FAIBE achieved was 98.3% under the optimum reaction condition and 95.2% after regeneration for six times. The viscosity–temperature curve of FAIBE was determined and the phase transition temperature was −1 °C. The pour point of FAIBE was only −10 °C, which exhibited excellent low temperature fluidity.In this study, Mg–Al–La composite oxide loaded with ionic liquid [Bmim]OH was used as a catalyst for the synthesis of fatty acid isobutyl ester (FAIBE) via transesterification between waste cooking oil and isobutanol. 相似文献