This work was supported by the University of Helsinki and the Jane and Aatos Erkko Foundation. S.H. thanks Erasmus+ EU funds for the fellowship.

1. Synthesis of Ag-Pd/ZrO2 NPs 
NOTE: In this procedure, the Pd mol% in Ag-Pd corresponded to 1%, and the Ag-Pd loading on ZrO2 corresponded to 3 wt.%.
<ol>
	<li>Place 1 g of ZrO2 powder in a 250 mL beaker.</li>
	<li>Add 50 mL of an AgNO3 (aq) (0.0059 mol/L) and 9.71 mL of a K2PdCl4 (aq) (0.00031 mol/L) solutions to the beaker under vigorous magnetic stirring (500 rpm) at room temperature.</li>
	<li>Add 10 mL ...

<ol>
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The authors have nothing to disclose.

The &#64257;ndings described in this method demonstrate that the intrinsic catalytic activity of Pd (or other catalytic but not plasmonic metal) can be signi&#64257;cantly enhanced by LSPR excitation via visible-light irradiation in bimetallic alloyed NPs35. In this case, Ag (or another plasmonic metal) is capable of harvesting energy from visible-light irradiation via LSPR excitation. The LSPR excitation leads to the formation of hot charge carriers (hot electrons and holes) and localized heating...

Among the several applications of metal nanoparticles (NPs), catalysis deserves special attention. Catalysis plays a central role in a sustainable future, contributing to less energy consumption, better utilization of raw materials, and enabling cleaner reaction conditions1,2,3,4. Thus, progress in catalysis can provide tools for enhancing the atomic efficiency of chemical processes, making them cleaner, more economically viable, and more environmentally friendly. Metal NPs encompassing silver (Ag), gold (Au) or copper (Cu) can display interesting optical properties in the visible range that arise from the unique way these systems interact with light at the nanoscale via the localized surface plasmon resonance (LSPR) excitation5,6,7,8. In these NPs, referred to as plasmonic NPs, the LSPR comprises the resonant interaction between the incident photons (from an incoming electromagnetic wave) with the collective motion of electrons5,6,7,8. This phenomenon takes place at a characteristic frequency which is dependent on the size, shape, composition, and dielectric constant of the environment9,10,11. For example, for Ag, Au, and Cu, these frequencies can range from the visible to the near-IR, opening up possibilities for the utilization of solar energy to excite their LSPR5,6,7,8,12,13.
Recently, it has been demonstrated that the LSPR excitation in plasmonic NPs can contribute to accelerate the rates and control the selectivity of molecular transformations5,14,15,16,17,18,19. This gave birth to a field called plasmonic catalysis, which focus on using energy from light to accelerate, drive, and/or control chemical transformations5,14,15,16,17,18,19. In this context, it has been established that the LSPR excitation in plasmonic NPs can lead to the formation of energetic hot electrons and holes, referred to as LSPR-excited hot carriers. These carriers can interact with adsorbed species through electronic or vibrational activation15,16. In addition to increased reaction rates, this process can also provide alternative reaction pathways not accessible via traditional thermochemically-driven processes, opening up new avenues for the control over reaction selectivity20,21,22,23,24,25. Importantly, it is worth noting that the plasmon decay can also lead to thermal dissipation, leading to a temperature increase in the vicinity of the NPs which can also contribute to speed up reaction rates15,16.
Due to these interesting features, plasmonic catalysis has been successfully employed towards a variety of molecular transformations18. Nevertheless, an important challenge remains. While plasmonic NPs such as Ag and Au display excellent optical properties in the visible and near-IR ranges, their catalytic properties are limited in terms of the scope of transformations. In other words, they do not display good catalytic properties for several of transformations. Additionally, metals that are important in catalysis, such as palladium (Pd) and platinum (Pt), do not support LSPR excitation in the visible or near-IR ranges. To bridge this gap, bimetallic NPs containing a plasmonic and catalytic metal represents an effective strategy20,26,27,28,29. In these systems, the plasmonic metal can be employed as an antenna to harvest energy from the light excitation through the LSPR, which is then used to drive, accelerate, and control molecular transformations at the catalytic metal. Therefore, this strategy enables us to extend plasmonic catalysis beyond traditional plasmonic metal NPs20,26,27,28,29.
This protocol describes the facile synthesis of bimetallic silver-palladium (Ag-Pd) alloyed NPs supported on ZrO2 (Ag-Pd/ZrO2) that can act as a plasmonic-catalytic system for plasmonic catalysis. The Ag-Pd/ZrO2 NPs were prepared by co-impregnation of the corresponding metal precursors on the ZrO2 support followed by simultaneous reduction30. This approach led to the formation of bimetallic NPs around 10 nm in size (diameter) directly at the surface of the ZrO2 support. The NPs were composed of 1 mol% of Pd to minimize the utilization of the catalytic metal while maximizing the optical properties of the resulting Ag-Pd NPs. A protocol for the application of the Ag-Pd/ZrO2 NPs in plasmonic catalysis was demonstrated for the reduction of nitrobenzene. We employed 425 nm LED illumination for the LSPR excitation. Gas chromatography was performed to monitor the conversion and selectivity of the reduction reaction under the dark and light irradiation conditions. LSPR excitation led to enhanced catalytic performance and control over selectivity in Ag-Pd/ZrO2 NPs relative to purely thermally driven conditions. The method described in this protocol is based on a simple photocatalytic reaction setup coupled with gas chromatography and can be adapted to a wide range of molecular transformations and NPs compositions. Thus, this method makes possible the characterization of photocatalytic activity, in terms of conversion and reaction selectivity, of different NPs and for a myriad of liquid-phase transformations. We believe this article will provide important guidelines and insights to both newcomers and more experienced scientists in the field.

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	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">2-Propanol (anhydrous, 99.5%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">278475</td>
			<td style="width:89px;">CAS Number 67-63-0</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Aniline (for synthesis)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.22256</td>
			<td style="width:89px;">CAS Number 62-53-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Azobenzene (98%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">424633</td>
			<td style="width:89px;">CAS Number 103-33-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Ethanol</td>
			<td style="width:96px;">Honeywell</td>
			<td style="width:114px;">32221</td>
			<td style="width:89px;">CAS Number 64-17-5</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Hydrochloric acid (37%)</td>
			<td style="width:96px;">VWR</td>
			<td style="width:114px;">PRLSMC310066</td>
			<td style="width:89px;">CAS Number 7647-01-0</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">L-Lysine (crystallized, &#8805;98.0% (NT))</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">62840</td>
			<td style="width:89px;">CAS Number 56-87-1</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Nitric acid (65%)</td>
			<td style="width:96px;">Merck</td>
			<td style="width:114px;">100456</td>
			<td style="width:89px;">CAS Number 7697-37-2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Nitrobenzene</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.06770</td>
			<td style="width:89px;">CAS Number 98-95-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Potassium hydroxide</td>
			<td style="width:96px;">Fisher</td>
			<td style="width:114px;">10448990</td>
			<td style="width:89px;">CAS Number 1310-58-3</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Potassium tetrachloropalladate (II) (98%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">205796</td>
			<td style="width:89px;">CAS Number 10025-98-6</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Silver nitrate (ACS reagent, &#8805;99.0%)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">209139</td>
			<td style="width:89px;">CAS Number 7761-88-8</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Sodium borohydride (fine granular for synthesis)</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">8.06373</td>
			<td style="width:89px;">CAS Number 16940-66-2</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:427px;">Zirconium (IV) oxide (nanopowder, &#60;100 nm particle size (TEM))</td>
			<td style="width:96px;">Sigma-Aldrich</td>
			<td style="width:114px;">544760</td>
			<td style="width:89px;">CAS Number 1314-23-4</td>
		</tr>
	</tbody>
</table>

preparation of silver-palladium alloyed nanoparticles for plasmonic catalysis under visible-light illumination

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular transformations. This opens possibilities for the use of visible or near-IR light as a sustainable input to drive and control reactions when plasmonic nanoparticles supporting LSPR excitation in these ranges are employed as catalysts. Unfortunately, this is not the case for several catalytic metals such as palladium (Pd). One strategy to overcome this limitation is to employ bimetallic NPs containing plasmonic and catalytic metals. In this case, the LSPR excitation in the plasmonic metal can contribute to accelerate and control transformations driven by the catalytic component. The method reported herein focuses on the synthesis of bimetallic silver-palladium (Ag-Pd) NPs supported on ZrO2 (Ag-Pd/ZrO2) that acts as a plasmonic-catalytic system. The NPs were prepared by co-impregnation of corresponding metal precursors on the ZrO2 support followed by simultaneous reduction leading to the formation of bimetallic NPs directly on the ZrO2 support. The Ag-Pd/ZrO2 NPs were then used as plasmonic catalysts for the reduction of nitrobenzene under 425 nm illumination by LED lamps. Using gas chromatography (GC), the conversion and selectivity of the reduction reaction under the dark and light irradiation conditions can be monitored, demonstrating the enhanced catalytic performance and control over selectivity under LSPR excitation after alloying non-plasmonic Pd with plasmonic metal Ag. This technique can be adapted to a wide range of molecular transformations and NPs compositions, making it useful for the characterization of the plasmonic catalytic activity of different types of catalysis in terms of conversion and selectivity.

Figure 1A shows digital photographs of the solid samples containing the pure ZrO2 oxide (left) and the Ag-Pd/ZrO2 NPs (right). This change in color from white (in ZrO2) to brown (Ag-Pd/ZrO2) provides the initial qualitative evidence on the deposition of Ag-Pd NPs at the ZrO2 surface. Figure 1B shows the UV-visible absorption spectra from the Ag-Pd/ZrO2 NPs (blue trace) as well as ZrO2 (...

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Preparation of Silver-Palladium Alloyed Nanoparticles for Plasmonic Catalysis under Visible-Light Illumination

Presented here is a protocol for the synthesis of silver-palladium (Ag-Pd) alloy nanoparticles (NPs) supported on ZrO2 (Ag-Pd/ZrO2). This system allows for harvesting energy from visible light irradiation to accelerate and control molecular transformations. This is illustrated by nitrobenzene reduction under light irradiation catalyzed by Ag-Pd/ZrO2 NPs.

Localized surface plasmon resonance (LSPR) in plasmonic nanoparticles (NPs) can accelerate and control the selectivity of a variety of molecular ...

This protocol represents the synthesis of silver palladium alloyed nanoparticles supported on zirconium dioxide. It facilitates the harvesting of energy from visible light irradiation to accelerate and control more light colored transformations. This method allows the matching of plasmonic and catalytic properties of a single line of particle to enable light trivalent transformations in catalytic metals that do not have plasmonic properties.This protocol can give insights into nanocatalysis, nanoparticle synthesis and supported catalyst synthesis. It can be applied to order molecular transformations in nanoparticle compositions. To fabricate silver palladium zirconium dioxide nanoparticles.Add 50 milliliters of silver nitrate and 9.71 milliliters of potassium tetrachloroplatinate to a 250 milliliter beaker containing one gram of zirconium dioxide. Mix the solutions under vigorous magnetic stirring at 500 revolutions per minute at room temperature for five minutes before adding 10 milliliters of lysine to the beaker. After 20 minutes, add 10 milliliters of a freshly prepared sodium borohydrid solution to the mixture drop wise at a rate of one milliliter per minute.Continue to stir the mixture for an additional 30 minutes at room temperature then allow the reaction to settle overnight. The next morning, split the suspension between several centrifuge tubes and separate the solids from the mixture by centrifugation. Carefully remove the supernatant and add 15 milliliters of deionized water to the tubes.Shake vigorously until the solid has been thoroughly dispersed placing the tubes in a vortex for one minute to fully resuspend the material as necessary. Repeat the centrifugation wash and resuspension two more times as demonstrated using 15 milliliters of deionized water for the second wash and ethanol for the third. After removing the ethanol from the last wash, dry the solid in a 60 degrees Celsius oven for 24 hours before characterizing the silver zirconium dioxide preparation by standard microscopy elemental and spectroscopic techniques.To produce silver zirconium dioxide nanoparticles add 50 milliliters of silver nitrate to a 250 milliliter beaker containing one gram of zirconium dioxide powder under vigorous magnetic stirring at room temperature, add 10 milliliters of lysine to the beaker and continue to stir the mixture for an additional 20 minutes. At the end of the incubation add 10 milliliters of freshly prepared sodium borohydride to the solution as demonstrated for a 30 minutes during incubation at room temperature. For separation and purification of the catalyst split the solution between several centrifuge tubes and collect the solids by centrifugation.Carefully remove the liquid phase and add 15 milliliters of deionized water to the tubes to allow a vigorous resuspension of the solids. Centrifuge the resulting solution for one additional wash with distilled water and one with ethanol as demonstrated. After removing the ethanol drive a solid in a 60 degrees Celsius oven for 24 hours before characterizing the silvers zirconium dioxide nanoparticles by a variety of standard microscopy elemental and spectroscopic techniques.To investigate the performance of the plasmonic catalyst under light illumination add 30 milligrams of catalyst to a 25 milliliter round bottom flask with a magnetic stir bar and add five milliliters of a 0.03 mole per liter nitrobenzene in isopropyl alcohol solution. Add 11.22 milligrams of potassium hydroxide powder to the flask and bubble this suspension with an argon flow for one minute to purge the reactor. Immediately after purging, place the sealed flask in a 70 degrees Celsius oil bath above a temperature controlled magnetic stirrer at 500 revolutions per minute.Use four LED lamps with a 427 nanometer wavelength and a 0.5 watts per square centimeter light intensity placed exactly seven centimeters away from the flask to irradiate the solution. And let the reaction proceed for 2.5 hours at 70 degrees Celsius under vigorous magnetic stirring. At the end of the incubation, turn off the lights and use a syringe and a needle to collect a one milliliter sample from the open reactor.Then strain the sample through a 0.45 micron filter into a glass chromatography vile to remove the catalyst particulate. To investigate the performance of the plasmonic catalyst in the absence of lighter radiation perform the analysis as just demonstrated but with the reaction container wrapped with aluminum foil to protect it from light. For gas chromatographic analysis prepare 10 milliliters of isopropyl alcohol solution containing approximately 30 millimoles per liter of nitrobenzene, 30 millimoles per liter of aniline and 30 millimoles per liter of azobenzene and run gas chromatography analysis on the solution according to standard protocols.The selected method should be able to separate the peaks corresponding to isopropyl alcohol, nitrobenzene, aniline and azobenzene in the minimum period of retention time as illustrated. Once the method has been selected prepare individual sets of solutions of 50, 25, 10, five and 2.5 millimolar nitrobenzene, aniline or azobenzene in isopropyl alcohol. Then run a gas chromatography analysis of each of the prepared solutions.Each chromatogram should present two peaks with the higher peak corresponding to isopropyl alcohol and the lower peak corresponding to nitrobenzene, aniline or azobenzene as appropriate. For each chromatogram note the retention time and peak area of each peak. Then plot the concentration versus peak area of each sample to trace the calibration curve to determine the concentration of each solvent.Zirconium dioxide does not display bans in the visible range and therefore should not contribute to any photocatalytic activity. A signal centered at 428 nanometers can be detected for the silvers zirconium dioxide nanoparticles while the silver palladium zirconium dioxide nanoparticles display a peak centered at 413 nanometers. It is difficult to identify silver palladium nanoparticles by scanning electron microscopy, but the formation of nanoparticles with a mean particle size of around 10 nanometers can be visualized by transmission electron microscopy.After the reaction the conversion and selectively for the formation of azobenzene and aniline can be measured by gas chromatography. In the absence of catalysts no nitrobenzene conversion is detected in the presence or absence of light illumination. For silver zirconium dioxide nanoparticles no conversion is detected in the dark while a 36%conversion is observed under LSPR excitation.A 56%selectivity toward azobenzene is also detected indicating that the silver alone can catalyze this reaction under LSPR excitation. For the bio metallic silver palladium zirconium dioxide nanoparticles no significant conversion is detected under dark conditions. Interestingly, under LSPR excitation the conversion is 63%with a 73%selectivity towards azobenzene, demonstrating the potential of the by metallic configuration to not only increase conversion under LSPR excitation but to also control reaction selectively.The reaction is catalytically driven by palladium and plus moronically enhanced by silver, under visible light irradiation. Therefore, controlling the nanoparticle synthesis and selecting the light wavelengths for catalysis are important. The catalytically active metal palladium and plasmonically active metal silver can be replaced with other types of possible combinations to target different types of organic reactions.

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5.3K 조회수.  University of Helsinki. This protocol represents the synthesis of silver palladium alloyed nanoparticles supported on zirconium dioxide. It facilitates the harvesting of energy from visible light irradiation to accelerate and control more light colored transformations. This method allows the matching of plasmonic and catalytic properties of a single line of particle to enable light trivalent transformations in catalytic metals that do not have plasmonic properties.This protocol can give insights into nanocata...