High-throughput Synthesis Of Metal Nanoclusters

Atomically precise metal nanocluster’s nuclei,consisting of tens to hundreds of metal atoms with nuclei in the 1-3 nanometer range,are an important bridge between metallic and non-metallic properties and key to helping understand metallicity formation.Metal nanoclusters protected by organic ligands can be stable in solution with homogeneous,precise structure and stable optical properties.In recent years,the research of atomic precision metal clusters has made rapid progress,and the precise synthesis of dozens to hundreds of metal atomic clusters has been realized.Metal clusters have a large number of application prospects in catalysis,biological probes,nanomedicine,etc.In recent years,the application of metal clusters in electrochemical carbon dioxide reduction has also received widespread attention.Exploring new metal nanocluster structures and applying metal nanoclusters in various fields has always been the research goal of researchers,but the current synthesis method and yield of metal nanoclusters restrict its development.In view of the research status in this field,in order to solve the problem that researchers need to complete a large number of repetitive synthesis work in the synthesis of metal nanoclusters,we independently designed and developed a high-throughput synthesis equipment for the synthesis of a large number of metal nanoclusters,screened the synthesis formula,developed a series of related equipment,and studied the structure and some catalytic properties of metal nanoclusters.The details are as follows:（1）The high-throughput synthesis equipment involves the synthesis field of artificial intelligence reactors,specifically a reaction platform and operating system for the synthesis of new materials,including reaction platform,operating system and optimization system;Through the operating system,the given reagent range can be divided and arranged to obtain different reaction ratios,and unnecessary reaction ratios can also be reduced by correlated reagents;The products are sampled and analyzed by the optimization system to determine the reaction ratio of the required products and optimize them as the basis for the next batch of reactions;The reaction stage has a precision syringe pump and an array of a number of magnetic stirrers,and magnetic shields are added to reduce the magnetic field of individual magnetic stirrers from the surrounding magnetic stirrers.The use of this equipment to complete the synthesis and screening of metal nanoclusters can complete dozens of times the workload of one worker in a short period of time,and liberate scientific research workers from repetitive work.The related low-temperature ultraviolet-fluorescence detection equipment discarded the addition of liquid nitrogen to cool down,and used the refrigeration mechanism to cool to meet the acquisition of UV/VIS absorption spectra and fluorescence emission spectra of metal nanoclusters in the temperature range of 77 K to 330 K.Turn the knob to complete the single-wavelength light source switching of ultra-multi-wavelength near-continuous LED light source,detect the photoluminescence and fluorescence quantum yield of metal nanoclusters,etc.LED solar simulator designed to detect the optical properties and catalytic performance of metal nanoclusters.（2）HAu Cl₄·3H₂O,Cd Cl₂·2.5H₂O were used to provide metal ions,C₇H₈OS was used as ligand,Na BH₄ was used as reducing agent,and dichloromethane and methanol were used as solvent.A simple and easy operation method was carried out to synthesize the metal nanoclusters used in the experiment,that is,the classical one-pot method to synthesize[Au₄₂Cd₄₀（C₇H₇OS）₅₂]^2-(abbreviated as Au₄₂Cd₄₀)nanoclusters of Au-Cd core-shell structure.Single crystals of brown Au₄₂Cd₄₀ nanoclusters were obtained by solvent diffusion.This is the first bimetallic nanocluster synthesized with a complete Au-CD core-shell structure.Single crystal X-ray crystallography（SC-XRD）proved that the nanocluster constructs a multi-level structure(Au₆@Au₃₆@Cd₄₀)by connecting shells,the innermost part is the Au₆ octahedral nucleus,which is wrapped by pear-like Au₃₆,because the Au₃triangle at the top is further surrounded by 9 gold atoms,and there are only 3 gold atoms at the bottom;In addition to the Au₄₂ nuclear structure composed of 42 gold atoms is a shell structure composed of 40 Cd atoms.Au₆ can generate tensile stresses on the outer Au₃₆ shell,and at the same time,the relatively hollow structure causes the Au₃₆ shell to shrink inward,and the presence of these two stresses makes the metal nanoclusters like Rupert’s tears in an unstable equilibrium.In the test range of 300-1100 nm wavelengths,the dichloromethane solution of Au₄₂Cd₄₀nanoclusters has multiple distinct absorption bands at 402,557,721 and 801 nm;The Au₄₂Cd₄₀ nanocluster emits near-infrared（NIR）photoluminescence peaks at 860 nm,and the quantum yield is about 0.38%under 405 nm excitation.Catalytic reaction of oxidation of styrene,Au₄₂Cd₄₀ nanoclusters can achieve an almost quantitative conversion rate（97-99%）,and the selectivity of benzaldehyde is 84.5%.（3）Au₄（PPh₃）I₂（abbreviated as Au₄）was synthesized by a pot method,and single crystals of orange-red Au₄ nanoclusters were obtained by solvent diffusion,which is the smallest superatom with free electrons currently reported.Three prepared samples,Au（I）P,Au4 and Au₁₁（PPh₃）₇I₃(abbreviated as Au₁₁),were loaded onto acidic multi-walled carbon nanotubes（CNTs）with a mass ratio of 1 to prepare catalysts.The catalytic performance of Au（I）P,Au₄ and Au₁₁ for electrochemical reduction of carbon dioxide（e CO₂RR）was significantly different,and Au（I）P complexes and Au₁₁ were able to convert carbon dioxide to carbon monoxide at all test potentials and had high FECO（>50%）.Au₄,on the other hand,only converts carbon dioxide to carbon monoxide at a high potential,and as the potential decreases,the main product becomes hydrogen.According to structural analysis,the length of the Au-Au bond is a key element of e CO₂RR.