What is the role of HEPES in the formation and stability of gold nano stars?

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Gold nanostar, many people may not know what material it is. Gold nanostar refers to gold particles shaped into stars. Gold particles can be sent to a tumor, manipulated by laser or magnetic field, and finally destroyed by heating malignant tumor cells. Nano Venus makes combustion hotter. Nano Venus is a new material to attack cancer. Now, researchers point out that gold particles can burn hotter if they are shaped into stars.

Among them, the common method to synthesize gold nano stars is to adopt the nuclear and surfactant free strategy of good's buffer HEPES, EPPs and mops. These reagents can be used as metal reducing agents, shape directing agents and stabilizers. Nano stars with different sizes and structures can be obtained by adjusting buffer concentration and solution pH. What is the relationship between HEPES and gold nanostar

Although HEPES is beneficial to the formation and structural stability of gold nanosars, little is known about the interaction between HEPES and metals. Recently, the reconstruction of gold nanostar induced by acidification was studied. It was found that its morphology depended on pH and acid composition, and was also affected by the protonation state of HEPES. Zeta potential and DFT method were used to measure the change of molecular proton state. Surface enhanced Raman spectroscopy (SERS) reveals that the change of pH induces the reversible activation of amine and sulfonic acid groups of HEPES, and the redistribution of electrons weakens the affinity between HEPES and metals, which is conducive to adsorption.

The experimental results show that the reconstruction of gold nano stars depends on the protons in the solution, which is consistent with the decomposition behavior of nanospheres with a diameter of about 6 nm under acid induction. In addition, the intensity and reconstruction rate of gold nano stars are related to the affinity of anions and gold. Through the study of the correlation between gold nanostar and HEPES, it is found that HEPES is partially replaced by benzene. When the adsorption of benzene or the chemical enhancement related to the sulfonic acid group of HEPES is weakened, HEPES will reorient. It is speculated that the partial desorption of HEPES and the change of electron distribution lead to reorientation.

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