Microwave-assisted Polyol Method Research Articles

Impact of Fe2(MoO4)3 and ZnMoO4 on CO Tolerance of Pt/C catalysts for enhanced methanol electrooxidation efficiency

Success of Pt/C catalyst in electrooxidation of methanol is highly influenced by its ability to withstand the poisoning effects of carbonaceous species adsorbed on the catalytic surface. Covalently bonded CO molecules occlude the active sites of the catalytic surface, impeding methanol adsorption. In this study, Pt/C-based nanocomposite catalysts were synthesized incorporating Fe2(MoO4)3 and ZnMoO4 to form heterojunctions through intermittent microwave-assisted polyol method to augment the CO oxidation pathway by introducing hydroxy groups adsorbed on their surfaces. Thorough characterization of the catalysts elucidated their chemical and phase purity, bonding configurations, and oxidation states, with various electroanalytical techniques employed to probe the mechanism of activity enhancement. Furthermore, the distinctive electron density profiles of these molybdate species have been identified as potential facilitators of methanol adsorption on the platinum surface. Equimolar composition in formulating the composite catalysts yielded a fivefold increase in catalytic activity (with ZnMoO4) and a 1.5-fold increase (with Fe2(MoO4)3). This approach demonstrates promise for tailoring Pt/C catalysts to develop industrially viable CO-tolerant and highly stable electrocatalysts.

Synthesis of Pd-Cu/TPPCu electrocatalyst for direct ethanol fuel cell applications

In this study, the electro-oxidation reaction of ethanol over Pd–Cu supported on Cu porphyrin (TPPCu) was investigated. The catalyst was synthesized using the microwave-assisted polyol method and physicochemically characterized by XRD, XPS, SEM, EDS, TEM, EDAX, UV–Vis, FTIR, and RBS. A Cu-enriched catalyst with Cu3Pd, Pd,Cu, and TPPCu phases was identified using XRD and XPS. However, according to the RBS results, the catalytic surface was enriched with Pd, indicating that the interaction between TPPCu and Pd–Cu allowed the presence of Pd on the surface, thus enhancing the catalytic response of the material. This synthesis prevented the deprotonation of porphyrin on the electrocatalyst, as confirmed by XPS analysis. Electrochemical studies based on cyclic voltammetry and electrochemical impedance spectroscopy were used to investigate the response of the catalyst to variations in the scan rate and increasing ethanol concentration. The electrochemical response of PdCu/TPPCu improved with an increasing number of cycles, indicating improved mass transport, thus improving its electrochemical response and tolerance to CO contamination. This catalyst exhibited a high electroactive surface area of 49.4 m2/g, which could be related to the presence of TPPCu as a support. The behavior of the catalyst on the anode of a fuel cell fed with ethanol, bioethanol, and bioethanol residues was evaluated.Graphical

Microwave-assisted synthesis of Pt/C catalyst at high temperatures for PEM fuel cells

In this work, Vulcan XC-72 supported platinum electrocatalysts (Pt/C) are synthesized by using a two-step, microwave-assisted polyol method. The effect of synthesis conditions on the properties of Pt/C electrocatalysts is investigated at various temperatures (140–200 °C) and corresponding autogenous-pressures (1.0–7.5 bar) at a constant synthesis duration of 35 min. A completely sealed reaction vessel is used to heat the polyol mixture above its boiling point of 140 °C. Catalysts are characterized by XRD, TGA, FTIR, BET, SEM, TEM, Cyclic voltammetry (CV), and the results are compared with the properties of commercial Pt/C. Pt/C catalyst synthesized at 160 °C exhibits the highest ECSA of 69.2 m2/g Pt, highest Pt loading efficiency of 92%, narrowest Pt particle size distribution with an average of 3.6 nm, and Pt crystallite size of 2.3 nm. SEM and TEM confirm the formation of micron-sized Pt agglomerations for the catalysts synthesized at 180 and 200 °C. Characterization studies show that the polyol method presented in this study is suitable for synthesizing Pt/C catalysts which have comparable properties to commercial Pt/C.

Synthesis and Characterization of Cobalt- Zinc Oxide Nanoparticles via Microwave assisted Polyol Method

This work involves the synthesis of cobalt zinc oxide nanoparticles using a simple green method and their characterization using various techniques. Green synthesis is carried out using polyol medium and microwave heating. Polyol medium minimizes the use of chemicals while microwaves provided an energy efficient method for heating. Ethylene glycol is used as solvent along with polyvinylpyrrolidone and hydrazinium hydroxide. Domestic microwave oven is used as source for microwaves. Nanoparticles collected after washing are calcined at three different temperatures: 773 K, 973K, 1173 K. They are characterized by using IR spectroscopy, X ray Diffraction, Energy Dispersive Spectroscopy and Transmission Electron Microscopy. EDS study confirmed composition and empirical formula of the samples calcined at different temperatures. XRD data included peaks for zinc oxide and cobalt oxide at characteristic 2θ values and calculated crystallite size as 32.07 nm at 773 K, 40.33nm at 973K and 56.42 at 1173 K. IR studies confirmed the formation of Zn-O, Co-O bonds and TEM images confirmed homogeneous size distribution. These nanoparticles are suitable for catalytic and antibacterial applications.

Nanocomposite Electrodes and Membranes for PEM Electrolysis

Reducing the iridium loading while keeping high mass activity and durability is one of the greatest challenges for PEMWE development.[1] Amongst the strategies to achieve this central goal, supporting iridium oxide on metal oxide supports offers high resistance to corrosion as well as electronic electrocatalyst-support interactions beneficial for catalyst activity and durability.[2] The morphology of the supports also plays a crucial role in the control of architecture and porosity of the catalyst layers.Here, tin oxide materials doped with aliovalent ions (niobium, antimony and tantalum)[3,4] were prepared by electrospinning leading to a fibre-in-tube morphology. The doping led to increase of the intrinsically low electrical conductivity of the semiconductor oxide. The electrochemical stability of the different supports was evaluated in acidic medium at low and high potentials, coupling electrochemistry and spectroscopic methods.[5] IrO2 nanoparticles synthesized by a microwave-assisted polyol method were deposited onto the doped SnO2 nanomaterials. Their electrochemical activity towards the oxygen evolution reaction (OER) as well as their durability upon accelerated stress tests were evaluated.In order to enhance the PEMWE performance, the use of thin membranes reducing resistive effects is crucial. To avoid premature failure and gas permeability issues, reinforcing polymer nanofibrous webs were introduced in the PFSA matrix.[6] The nanocomposite membranes obtained led to greater mechanical robustness and reduced gas crossover while keeping high proton conductivity. [7]The nanocomposite electrocatalysts and membranes were used to prepare membrane-electrode assemblies and characterised in a PEMWE cell. Their performance and stability were investigated in different operating conditions and will be discussed. Daiane Ferreira da Silva, C.; Claudel, F.; Martin, V.; Chattot, R.; Abbou, S.; Kumar, K.; Jiménez-Morales, I.; Cavaliere, S.; Jones, D.; Rozière, J.; et al. Oxygen Evolution Reaction Activity and Stability Benchmarks for Supported and Unsupported IrO x Electrocatalysts. ACS Catal. 2021, 11, 4107–4116.Du, L.; Shao, Y.; Sun, J.; Yin, G.; Liu, J.; Wang, Y. Advanced catalyst supports for PEM fuel cell cathodes. Nano Energy 2016, 29, 314–322.Cavaliere, S.; Jiménez-Morales, I.; Ercolano, G.; Savych, I.; Jones, D.; Rozière, J. Highly Stable PEMFC Electrodes Based on Electrospun Antimony-Doped SnO2. ChemElectroChem 2015, 2, 1966–1973.Jiménez-Morales, I.; Haidar, F.; Cavaliere, S.; Jones, D.; Rozière, J. Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction. ACS Catal. 2020, 10, 10399–10411.Jiménez-Morales, I.; Cavaliere, S.; Dupont, M.; Jones, D.; Rozière, J. On the stability of antimony doped tin oxide supports in proton exchange membrane fuel cell and water electrolysers. Sustain. Energy Fuels 2019, 3, 1526–1535.Sood, R.; Cavaliere, S.; Jones, D.J.; Rozière, J. Nano Energy Electrospun nano fi bre composite polymer electrolyte fuel cell and electrolysis membranes. Nano Energy 2016, 26, 729–745.Sood, R.; Giancola, S.; Donnadio, A.; Zatoń, M.; Donzel, N.; Rozière, J.; Jones, D.J.; Cavaliere, S. Active electrospun nanofibers as an effective reinforcement for highly conducting and durable proton exchange membranes. J. Memb. Sci. 2021, 622.

Design of Pt-Sn-Zn Nanomaterials for Successful Methanol Electrooxidation Reaction.

This work highlights the potential for the synthesis of new PtSnZn catalysts with enhanced efficiency and durability for methanol oxidation reaction (MOR) in low-temperature fuel cells. In this research, PtZn and PtSnZn nanoparticles deposited on high surface area Vulcan XC-72R Carbon support were created by a microwave-assisted polyol method. The electrochemical performances of synthesized catalysts were analyzed by cyclic voltammetry and by the electrooxidation of adsorbed CO and the chronoamperometric method. The physicochemical properties of obtained catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TGA) analysis, energy dispersive spectroscopy (EDS) and by X-ray diffraction (XRD). The obtained findings showed the successful synthesis of platinum-based catalysts. It was established that PtSnZn/C and PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. Catalysts stability tests were obtained by chronoamperometry. Stability tests also confirmed decreased poisoning and indicated improved stability and better tolerance to CO-like intermediate species. According to activity and stability measurements, the PtSnZn/C catalyst possesses the best electrochemical properties for the methanol oxidation reaction. The observed great electrocatalytic activity in the methanol oxidation reaction of synthesized catalysts can be attributed to the beneficial effects of microwave synthesis and the well-balanced addition of alloying metals in PtSnZn/C catalysts.

Effect of uniformity and surface morphology of Pt nanoparticles to enhance oxygen reduction reaction in polymer electrolyte membrane fuel cells

Platinum (Pt)-based electrocatalysts supported by reduced graphene oxide (rGO) is fabricated under microwave-assisted polyol method with various nucleation and growth conditions. The surface morphologies of the Pt nanoparticles (NPs) under various reaction conditions owing to different Pt NP sizes and inter-particle spacings are investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, cyclic and linear sweep voltammetry, and electrochemical impedance spectroscopy. The synthesized Pt/rGO catalyst under nucleation and growth times of 10 s and 50 s, respectively, exhibits excellent catalytic activity with increased electrochemical surface area, high density, good uniformity and surface morphology with a particle size and inter-particle spacing of 2.16 nm and 17.2 nm, respectively. These results elucidate the relationship between the Pt NP morphology distribution and oxygen reduction reaction of catalysts in polymer electrolyte membrane fuel cell systems. We also highlight the important role of size and inter-particle spacing on the Pt electrochemical catalystic performance.

Platinum nanoparticles deposited on Cu-doped NiO/C hybrid supports as high-performance catalysts for ethanol and glycerol electrooxidation in alkaline medium

In this work, the influence of Cu-doping on the ability of NiO co-catalyst to enhance the electrocatalytic properties of carbon-supported Pt nanoparticles toward ethanol and glycerol oxidation was investigated. The Cu-doped NiO particles were synthesized by a precipitation method, while the noble metal nanoparticles were deposited over the hybrid Cu-doped NiO/C supports via a pulsed microwave-assisted polyol method using ethylene glycol as reductant. Pt-NiO and Pt-NiOCuO(x:y)/C catalysts with Ni:Cu atomic ratios of 9:1 (Pt-NiOCuO(9:1)/C), 7:3 (Pt-NiOCuO(7:3)/C) and 5:5 (Pt-NiOCuO(5:5)/C) were obtained. The physicochemical analysis showed that the as-prepared catalysts are composed of nanoparticles of about 3 nm. The potentiostatic experiments exhibited that the Pt-NiOCuO(7:3)/C catalyst is the most active catalyst for ethanol oxidation, while the Pt-NiOCuO(5:5)/C catalyst exhibited the best performance for glycerol oxidation. These catalysts developed mass current densities of almost 12 and 5 times higher than those of bare Pt/C for ethanol and glycerol oxidation reactions, respectively. Moreover, an accelerated multicycling stability test displayed that the as-prepared catalysts retain almost 98% of their initial mass current density.

Targeted dielectric coating of silver nanoparticles with silica to manipulate optical properties for metasurface applications

An epsilon-negative metamaterial (ENM) containing core@shell nanoparticles (NPs) was designed, where silver (Ag) NPs served as core and silica (SiO2) was used as spacer shell. AgNPs were synthesized in large scale, using microwave-assisted polyol method, in three average particle sizes, as 30, 54, and 61 nm, with a narrow particle size distribution. Optical absorption of Ag NPs was investigated using UV–Vis spectroscopy. Their optical behavior was also theoretically predicted for different thicknesses of the SiO2 shell immersed in media of different refractive indices using the Clausius - Mossotti equation. Based on the results, optimal outputs were obtained with a SiO2 shell of 10 nm in thickness encompassing 54 nm Ag NPs based on the analytical model and numerical simulations here developed for core-shell structures. Then 10 nm SiO2 shell was grown on 54 nm Ag NPs by sol-gel synthesis. The NPs were then characterized by UV–Vis, TEM, SEM, EDX, DLS, and zeta potential analyses. The synthesized core-shell NPs can be used to establish epsilon-negative properties in polymer layers within visible range of wavelengths.

γ-Fe2O3 nanoflowers as efficient magnetic hyperthermia and photothermal agent

Recent reports on the magnetic nanoparticles (MNPs) as an efficient and alternative photothermal agent have excited the researchers worldwide. While MNPs have been explored well for high heating performance during magnetic hyperthermia (MHT), their full potential is yet to be explored as an efficient photothermal agent. In addition, the simultaneous exposure of alternating magnetic field (for MHT) and near infrared irradiation (for photothermal therapy PTT) can drastically enhance the heating behaviour of MNPs. In the present work we explored microwave assisted polyol method to get γ-Fe2O3 nanoflowers. The use of sodium acetate in varying amounts, as an alkali source, allowed the modification of structural and magnetic properties leading to the formation of nanoflower with high heating performance during MHT and PTT. Role of defects in γ-Fe2O3 nanoflowers were investigated using photoluminescence spectroscopy which highlighted distinct role of oxygen vacancies and surface states. The nanoflowers with better crystallinity and relatively higher coercive field performed well during MHT. The observed high intrinsic loss power value of 15.21 ± 0.34 nHm2Kg-as significantly higher than the commercially available ferrofluids and previously reported values for nanoflowers. During PTT, the therapeutic temperature of 42 °C was achieved for the aqueous suspension with a concentration as low as 100 µg/mL which demonstrates the superiority of γ-Fe2O3 nanoflowers as an efficient PTT agent.

Characterization and electrochemical properties of Pt nanoparticles deposited on titanium oxide nanofibers

To overcome problems with carbon corrosion, titanium oxide nanofibers (TNFs) were investigated as alternative supports for the deposition of Pt nanoparticles. In this work, pristine or Nb-doped TNFs were prepared using an electrospinning technique. Pt nanoparticles were deposited on the selected TNFs using a microwave-assisted polyol method. Nb doping and heat treatment in reducing atmospheres significantly affected the fiber diameter, grain size, oxygen vacancies, and electrical conductivity of the TNFs. The incorporation of Nb into the TiO2 lattice inhibited grain growth and phase transition in an oxidizing atmosphere. However, heat treatment in a reducing atmosphere resulted in a significant increase in grain size. As a result of Nb doping associated with heat treatment at 800 °C in a reducing atmosphere, all the anatase phase was converted to the rutile phase. In addition, Ti4+ was reduced to Ti3+, and Nb5+ was reduced to Nb4+. These transformations could be the basis for high electrical conductivity. The electrochemical surface area (ECSA) of Pt/Nb-TNF800 was 48 m2/g. The durability of the ECSA of this material was much distinguished compared to that of a commercial Pt/C catalyst.

Engineering Iron Oxide Nanocatalysts by a Microwave-Assisted Polyol Method for the Magnetically Induced Degradation of Organic Pollutants.

Advanced oxidation processes constitute a promising alternative for the treatment of wastewater containing organic pollutants. Still, the lack of cost-effective processes has hampered the widespread use of these methodologies. Iron oxide magnetic nanoparticles stand as a great alternative since they can be engineered by different reproducible and scalable methods. The present study consists of the synthesis of single-core and multicore magnetic iron oxide nanoparticles by the microwave-assisted polyol method and their use as self-heating catalysts for the degradation of an anionic (acid orange 8) and a cationic dye (methylene blue). Decolorization of these dyes was successfully improved by subjecting the catalyst to an alternating magnetic field (AMF, 16 kA/m, 200 kHz). The sudden temperature increase at the surface of the catalyst led to an intensification of 10% in the decolorization yields using 1 g/L of catalyst, 0.3 M H2O2 and 500 ppm of dye. Full decolorization was achieved at 90 °C, but iron leaching (40 ppm) was detected at this temperature leading to a homogeneous Fenton process. Multicore nanoparticles showed higher degradation rates and 100% efficiencies in four reusability cycles under the AMF. The improvement of this process with AMF is a step forward into more sustainable remediation techniques.

Energy resolved-electrochemical impedance spectroscopy investigation of the role of Al-doped ZnO nanoparticles in electronic structure modification of polymer nanocomposite LEDs

The work is focused on power efficiency and luminance of polymer light-emitting diodes (PLED) based on polymer matrix and nanoparticulate filler. As polymer matrices poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) were used. Nanofillers, aluminium-doped ZnO nanoparticles, were prepared by microwave-assisted polyol method and characterized by XRD, SEM, and TEM. Obtained nanoparticle colloids were mixed with dissolved polymer. Then, nanocomposite active layers of prepared PLEDs were spin-cast in one processing step. Specific optoelectronic and electric properties of nanocomposite materials and performance of PLED devices were investigated using UV–Vis absorption, photoluminescence, energy-resolved electrochemical impedance spectroscopy (ER-EIS), and I-V and luminance measurements. The addition of Al-doped ZnO nanoparticles improved power efficiency of diodes exhibiting an order of magnitude enhancement in electroluminescence intensity, luminance (from 1900 to 20700 cd/m2 for MEH-PPV and from 4600 to 38000 cd/m2 for F8BT) and had pronounced effect on opening bias voltage of final devices. In addition, two effects of nanoparticulate doping were revealed. The first, specific one, related with electronic structure of used nanoparticles. The second, non-specific, which indirectly contributes to structural ordering of the polymer matrix. Observed phenomena are related to electronic band structure affected by the addition of nanoparticles as revealed by ER-EIS.

Surface Functionalization of Ordered Mesoporous Hollow Carbon Spheres with Ru Organometallic Compounds as Supports of Low-Pt Content Nanocatalysts for Alkaline Hydrogen and Oxygen Evolution Reactions

AbstractHerein, we report a methodology that leads to the formation of Ru metallic sites, followed by the development and anchorage of Pt-Ru alloyed nanoparticles on the surface of Ordered Mesoporous Hollow Carbon Spheres (OMHCS). Along with the Ru sites, it is demonstrated that the functionalization promotes the formation of functional groups on the surface of the OMHCS. In a first stage, OMHCS are functionalized with the [(η6-C6H5OCH2CH2OH)RuCl2]2 (Ru-dim) and [(η6-C6H4CH(CH3)2CH3)RuCl2]2 (Ru-cym) organometallic compounds. Afterwards, Pt nanoparticles are dispersed by the microwave-assisted polyol method over the functionalized supports obtaining the low-metal content 5 wt. % Pt/OMHCSRu-dim and Pt/OMHCSRu-cym nanocatalysts. The degree of Ru alloyed is found to be around 35%. The low-Pt content Pt/OMHCSRu-cym and Pt/OMHCSRu-dim exhibit a higher catalytic activity for the Oxygen (OER) and the Hydrogen (HER) Evolution Reactions than the Pt/C benchmark and the Pt/OMHCS nanocatalysts. The overpotential for the OER at 10 mA cm-2 (ηOER) is 300 mV and 210 mV smaller at Pt/OMHCSRu-cym and Pt/OMHCSRu-dim compared to Pt/C, respectively. The corresponding values of the HER at -10 mA cm-2 (ηHER) are 14 and 18 mV smaller, respectively. The high catalytic activity of Pt/OMHCSRu-cym and Pt/OMHCSRu-dim has been attributed in part to the presence of Ru0 and RuO2 species from organometallic functionalization, and the modification of the d-valence band of Pt. Their high performance for the OER and the HER opens new lines of research for the design of nanocatalysts for alkaline electrochemical water splitting.

Hydrogenation of High Molecular Weight Bisphenol A Type Epoxy Resin BE503 in a Functional and Greener Solvent Mixture Using a Rh Catalyst Supported on Carbon Black.

A functional greener solvent mixture containing water, isopropyl alcohol (IPA) and ethyl acetate with the ratio 10:20:70 (wt%) was found to accelerate hydrogenation of bisphenol A type epoxy resin BE503 with a molecular weight of 1500 through an on-water mechanism, and led to an increased H2 availability, due to high solubility of H2 in IPA. Different carbon-based supports were tested and VulcanXC72 was found as the best support among the tested carbon-based ones as it possessed the highest amount of electron deficient promoter, RhOx. The catalyst, Rh5/VulcanXC72-polyol, synthesized by the microwave assisted polyol method, yielded a 100% hydrogenation of aromatic rings with an epoxy ring opening below 20.0% at 50 °C and a H2 pressure of 1000 psi in 2.25 h. Intrinsic activation energies for the hydrogenation of aromatic rings and epoxy ring opening were experimentally estimated and a mechanism for the hydrogenation of BE503 was proposed, wherein the hydrogenation of aromatic rings and epoxy ring opening in BE503 proceeded simultaneously in parallel and in-series with parallel being the major pathway.

Enhanced antibacterial activity of Ag-doped ZnS nanoparticles synthesised by a microwave-assisted polyol method

ABSTRACT Silver doped zinc sulphide nanoparticles were synthesised by a microwave-assisted polyol method. Characterisation of nanoparticles was performed using XRD, FESEM-EDXand UV-visible spectroscopy to investigate chemical structure, crystalline phase, particle size and surface morphology. Antibacterial properties of synthesised nanoparticles were investigated by determining their MIC and MBC values and kinetic of bactericidal activity against Staphylococcus aureus(ATCC 6538) and Escherichia coli(ATCC 25922). Characterisation of the synthesised nanoparticles showed formation of single phase of hexagonal wurtzite ZnS structure with Ag+ substitution at 1.6% Zn/Ag molar ratio. MIC values were determined as 250 and 500 µg/ml against Staphylococcus aureus and Escherichia coli, respectively and time kill profiles showed efficient and rapid bactericidal activity of the synthesised Ag-doped ZnS nanoparticles. Results of this study suggest a synthesis strategy for Ag-doped ZnS nanoparticles with potent and broad spectrum antibacterial properties that can widen the range of applications of these nanoparticles.

Modeling, design, and synthesis of gram-scale monodispersed silver nanoparticles using microwave-assisted polyol process for metamaterial applications

High-yield monodispersed silver (Ag) nanospheres were modeled, designed, and synthesized by microwave-assisted (MW-assisted) polyol method from AgNO 3 , polyvinyl pyrrolidone (PVP), and ethylene glycol (EG), as precursors, at 145 °C within a short reaction time of 2 min, and the results were compared to those of conventional polyol method. Maintaining the PVP:AgNO 3 molar ratio, the effect of increasing the amounts of AgNO 3 and PVP at a constant amount of EG (40 mL) on the final product was evaluated. The synthesized nanoparticles (NPs) were characterized by SEM, UV–Vis spectroscopy, FTIR and DLS analysis. The results showed that with increasing the amount of AgNO 3 to 0.5 and 1 g, monodispersed Ag nanoparticles (Ag NPs) with particle sizes of 54 and 61 nm were formed, as per the plasmon absorption peaks at 436 and 442 nm, respectively. Moreover, using 40 mL of the EG solution, we could obtain a high yield of the NPs (~90%). The sub-gram yield was excellently high, offering great opportunities for commercializing the procedure. Also, the proposed study paves a new way for Ag NPs realization for different practical applications ranging from MW to optics. • Mathematical description of the electromagnetic and thermal interaction obtained between the impinging waves and AgNPs. • New MW-assisted polyol process used to synthesized very high yield AgNPs. • The obtained yield corresponded to a significant fraction of a gram as well as higher degrees of monodispersity.

Pt-based trimetallic nanocrystals with high proportions of M (M=Fe, Ni) metals for catalyzing oxygen reduction reaction

For boosting oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs), a new type of multi-functional catalyst with high activity, high stability, and low cost has been designed and prepared by introducing high proportions of M (M = Fe, Ni) metals in Pt-based nanoparticles through a microwave-assisted polyol method, followed by thermal annealing process. A uniform dispersion of nanoparticles (5 nm) and a face-centered tetragonal (fct) phase improve the activity and stability of the Pt–Fe–Ni/C catalyst. Owing to differences in the surface energies of the alloying elements, Pt atoms with low surface energy have a tendency to segregate from the subsurface to the surface during the annealing. This tendency exposes the internal Pt atoms to the surface of the nanoparticles in the existence of high proportions of M metals, significantly improving the utilization of Pt. As a cathode catalyst, the Pt–Fe–Ni/C catalyst annealed at 675 °C with a mass activity of 0.73 A/mgPt, which is 3.5 times higher than that of the commercial Pt/C catalyst, exhibits an excellent half-cell performance. An accelerated durability test demonstrates that the prepared Pt–Fe–Ni/C-675 catalyst is more stable than the commercial Pt/C. The proposed multi-functional catalyst has great potential for PEMFCs and other applications.

Tunable Photoluminescence of Carbon Dots used for Homogeneous Glucose Sensing Assay

Carbon dots (CDs) with tunable photoluminescence in a large range (80 nm) are produced by a microwave-assisted polyol method. The emission of CDs in aqueous can be adjusted by simply changing the precursors’ concentrations. The CDs with tunable photoluminescence have been further functionalized to develop a homogeneous glucose biosensor by incorporating with enzyme-conjugated graphene oxide. The fluorescence of CDs can be quenched through covalently interacting with the graphene oxide. The restored fluorescence is observed in the presence of glucose. The performance of the homogeneous sensing system has been evaluated by testing glucose levels in a range from 0.2 mM to 10 mM. Two linear relationships of the restored fluorescence intensity as a function of the concentration of glucose are obtained, i.e. 2 mM to 10 mM, and 0.2 mM to 1 mM, respectively. In addition, streptozotocin-induced diabetic rats are utilized to evaluate the performance of the designed sensor for testing diabetic rat’s plasma glucose. The results demonstrate that the homogeneous carbon-based biosensor can measure glucose in the blood and in other conditions.

Testing the predictive power of theory for PdxIr(100−x) alloy nanoparticles for the oxygen reduction reaction

PdxIr(100−x) alloys synthesized via a microwave-assisted polyol method serve as an ideal experimental system to improve theoretical insight of the material properties towards the ORR.