Suzuki-Miyaura Cross-Coupling Using Plasmonic Pd-Decorated Au Nanorods as Catalyst: A Study on the Contribution of Laser Illumination

The interaction between plasmonic metal catalysts and visible light can be exploited to increase their catalytic activity. This activity increase results from the generation of hot charge carriers or hot surfaces, or a combination of both. We have studied the light‐induced Suzuki‐Miyaura cross‐coupling reaction of bromobenzene and m‐tolylboronic acid using Pd‐decorated Au nanorods as plasmonic catalyst in order to assess which physical effect dominates. Comparative experiments under laser illumination and in dark were performed, demonstrating that under the experimental conditions applied in our study the catalytic activity achieved upon illumination is dominantly based on the conversion of light to heat by the plasmonic catalyst. Pd leached from the catalyst also plays a significant role in the reaction mechanism

Rheological response of a modified polyacrylamide–silica nanoparticles hybrid at high salinity and temperature

Water-soluble polyacrylamides have often been used to modify flow response in various water-based technologies and industrial processes, including paints, water treatment, paper manufacturing, and chemical enhanced oil recovery. Polymers are susceptible to degradation at combined high salinity and elevated temperature conditions which limits their overall performance. Hybrid mixtures of hydrophobically modified polyacrylamide (HMPAM) with hydrophobically modified silica nanoparticles (NPs) emerged as a promising strategy for achieving enhanced stability and high viscosity in brines having a high total dissolved solids (TDS) content and high hardness at elevated temperatures (>20 wt% TDS, including >1.5 wt% divalent cations at T > 70 °C). The rheological response of the hybrids at various concentrations of HMPAM and NPs was examined to investigate the synergic effects. Hybridization of HMPAM with NPs led to a higher viscosity at high salinity and elevated temperature. The viscosity improvement was more pronounced when the concentration of HMPAM was in the semi-dilute regime and concentration of NPs was higher than a critical threshold where the viscosity increased roughly by a factor of 1.5. Here we present the mechanisms of improved viscosity behaviour. The rheological data suggest the role of NPs in the bridging between HMPAM molecules, which in turn increases the hydrodynamic radius and consequently the viscosity of the hybrids

Suzuki-Miyaura Cross-Coupling Using Plasmonic Pd-Decorated Au Nanorods as Catalyst: A Study on the Contribution of Laser Illumination

The interaction between plasmonic metal catalysts and visible light can be exploited to increase their catalytic activity. This activity increase results from the generation of hot charge carriers or hot surfaces, or a combination of both. We have studied the light‐induced Suzuki‐Miyaura cross‐coupling reaction of bromobenzene and m‐tolylboronic acid using Pd‐decorated Au nanorods as plasmonic catalyst in order to assess which physical effect dominates. Comparative experiments under laser illumination and in dark were performed, demonstrating that under the experimental conditions applied in our study the catalytic activity achieved upon illumination is dominantly based on the conversion of light to heat by the plasmonic catalyst. Pd leached from the catalyst also plays a significant role in the reaction mechanism

Rheological response of a modified polyacrylamide–silica nanoparticles hybrid at high salinity and temperature

Water-soluble polyacrylamides have often been used to modify flow response in various water-based technologies and industrial processes, including paints, water treatment, paper manufacturing, and chemical enhanced oil recovery. Polymers are susceptible to degradation at combined high salinity and elevated temperature conditions which limits their overall performance. Hybrid mixtures of hydrophobically modified polyacrylamide (HMPAM) with hydrophobically modified silica nanoparticles (NPs) emerged as a promising strategy for achieving enhanced stability and high viscosity in brines having a high total dissolved solids (TDS) content and high hardness at elevated temperatures (>20 wt% TDS, including >1.5 wt% divalent cations at T > 70 °C). The rheological response of the hybrids at various concentrations of HMPAM and NPs was examined to investigate the synergic effects. Hybridization of HMPAM with NPs led to a higher viscosity at high salinity and elevated temperature. The viscosity improvement was more pronounced when the concentration of HMPAM was in the semi-dilute regime and concentration of NPs was higher than a critical threshold where the viscosity increased roughly by a factor of 1.5. Here we present the mechanisms of improved viscosity behaviour. The rheological data suggest the role of NPs in the bridging between HMPAM molecules, which in turn increases the hydrodynamic radius and consequently the viscosity of the hybrids.Petroleum EngineeringChemE/Product and Process Engineerin

Low Temperature Sunlight-Powered Reduction of CO₂ to CO Using a Plasmonic Au/TiO₂ Nanocatalyst

Sunlight-powered reduction of CO2 to fuels and chemicals is a promising strategy to close the carbon loop and facilitate the energy transition. In this research, we demonstrate that Au nanoparticles supported on TiO2 are an efficient plasmonic catalyst for the sunlight-powered reverse water-gas shift (rWGS) reaction. A maximum CO production rate of 429 mmol ⋅ gAu−1 ⋅ h−1 with a selectivity of 98 % and an apparent quantum efficiency of 4.7 % were achieved using mildly concentrated sunlight (1.44 W ⋅ cm−2 equals 14.4 sun). The CO production rate showed an exponential increase with increasing light intensity, suggesting that the process is mainly promoted by a photothermal effect. Thermal reference experiments with the same catalysts promoted CH4 formation, dropping the CO selectivity to 70 %. Thus, mildly concentrated sunlight can efficiently and selectively enhance the promotion of the rWGS reaction without using external heating.ImPhys/Optic

Continuous-Flow Sunlight-Powered CO₂ Methanation Catalyzed by γ-Al₂O₃-Supported Plasmonic Ru Nanorods

Plasmonic CO2 methanation using γ-Al2O3-supported Ru nanorods was carried out under continuous-flow conditions without conventional heating, using mildly concentrated sunlight as the sole and sustainable energy source (AM 1.5, irradiance 5.5–14.4 kW·m−2 = 5.5–14.4 suns). Under 12.5 suns, a CO2 conversion exceeding 97% was achieved with complete selectivity towards CH4 and a stable production rate (261.9 mmol·g−1 Ru·h−1) for at least 12 h. The CH4 production rate showed an exponential increase with increasing light intensity, suggesting that the process was mainly promoted by photothermal heating. This was confirmed by the apparent activation energy of 64.3 kJ·mol−1, which is very similar to the activation energy obtained for reference experiments in dark (67.3 kJ·mol−1). The flow rate influence was studied under 14.4 suns, achieving a CH4 production plateau of 264 µmol min−1 (792 mmol·g−1 Ru·h−1) with a constant catalyst bed temperature of approximately 204◦C.ImPhys/Optic

Using Fiber Bragg Grating Sensors to Quantify Temperature Non-Uniformities in Plasmonic Catalyst Beds under Illumination

Distinguishing between photothermal and non-thermal contributions is essential in plasmon catalysis. Use of a tailored optical temperature sensor based on fiber Bragg gratings enabled us to obtain an accurate temperature map of an illuminated plasmonic catalyst bed with high spatiotemporal resolution. Its importance for quantification of the photothermal and non-thermal contributions to plasmon catalysis is demonstrated using a Ru/Al2O3 catalyst. Upon illumination with LEDs, we measured temperature differences exceeding 50 °C in the top 0.5 mm of the catalyst bed. Furthermore, we discovered differences between the surface temperature and the temperature obtained via conventional thermocouple measurements underneath the catalyst bed exceeding 200 °C at 2.6 W cm−2 light intensity. This demonstrates that accurate multi-point temperature measurements are a prerequisite for a correct interpretation of catalysis results of light-powered chemical reactions obtained with plasmonic catalysts.ImPhys/Optic