Free silver nanoparticles doped by potassium : work-function change in experiment and theory

Abstract

<div lang="en" class="abs"><p class="abs_header">Abstract</p><p>The composition-dependent change in the work-function (<em>WF</em>) of binary silver–potassium nanoparticles has been studied experimentally by synchrotron-based x-ray photoelectron spectroscopy (PES) and theoretically using a microscopic jellium model of metals. The Ag–K particles with different K fractions were produced by letting a beam of preformed Ag particles pass through a volume with K vapor. The PES on a beam of <em>individual non-supported</em> Ag–K nanoparticles created in this way allowed a direct absolute measurement of their <em>WF</em>, avoiding several usual shortcomings of the method. Experimentally, the <em>WF</em> has been found to be very sensitive to K concentration: Already at low exposure, it decreased down to ≈2 eV—below the value of pure K. In the jellium modeling, considered for Ag–K nanoparticles, two principally different adsorption patterns were tested: without and with K diffusion. The experimental and calculation results together suggest that only efficient surface alloying of two metals, whose immiscibility was long-term textbook knowledge, could lead to the observed <em>WF</em> values.</p></div>