## 1 Introduction
We are interested in the following studies related to the inactivation of viruses by Cu\({}_{2}\)O: (1) The high antibacterial efficacy of Cu\({}_{2}\)O suggests that oxide formation on copper objects in a dry atmosphere does not impair their efficiency as an antimicrobial measure. The influences of bacteria-metal interaction, media composition, and copper surface chemistry on contact killing are not fully understood [7; 8; 9]. (2) Cu\({}_{2}\)O has a unique antiviral mechanism mediated by direct contact [10; 11]. (3) The preparation of small-sized nano Cu\({}_{2}\)O particles on halloysite nanotubes has been carried out. Most importantly, HNTs with positive charges on the surface could enhance their interaction with bacteria and cause physical damage [12; 13]. (4) The specimens, which existed as mainly Cu\({}^{0}\) or Cu\({}^{+}\) on the surface, exhibit the same corrosion behavior and promote the elution of Cu ions due to the presence of _E. coli_ in the immersion solution. In contrast, the release of Cu ions from the specimen that existed mainly as Cu\({}^{2+}\) does not change in the presence of bacteria [14; 15; 16; 17]. (5) Photo-electro-Fenton reaction and surface hydroxyl groups [18; 19; 20; 21; 22] and biocorrosion stability and biosynthesis of metal oxide nanoparticles [23; 24] are of great importance. Further, from the cathodic reduction of copper oxides (CuO and Cu\({}_{2}\)O) in a strongly alkaline electrolyte [25], it is assumed that there is a limiting thickness of the Cu\({}_{2}\)O layer. This results from competition of the disproportionation reaction (Cu + CuO\(\rightarrow\)Cu\({}_{2}\)O) and CuO formation (Cu\({}_{2}\)O + (1/2)O\({}_{2}\)\(\rightarrow\)2 CuO), and it is suggested that Cu(OH)\({}_{2}\) plays an initial key role in the growth of the corrosion layer. Surface processes are further diversified by acid-base interactions at the surface overlayer. Acid-base reactions between adsorbates and metal oxides or hydroxides/metals are strongly influenced by electron donors/acceptors governing the _ET_ behavior at the surface overlayer. We developed an extremely sensitive surface analysis technique of _ET_ using photoelectron emission (PE), which is measured as a function of temperature. This method is called temperature-programmed photoelectron emission (TPPE). We have reported several papers on TPPE [26; 27; 28]. The TPPE feature for the surfaces of 17 commercial metals was correlated with their surface chemical structure measured by XPS [27; 28]. The metals used were distinctly classified into two main groups (A and B): the former indicated a temperature-dependent PE total count, while the latter indicated a virtually temperature-independent PE total count. The A group included Al, Pt, Pb, Cu, Ag, Au, and Ni; the B group included Ta, Ti, Mo, Pd, W, Fe, Co, Zn, Nb, and Sn [27; 28]. Further, we found that when a copper electrode was used in the electrochemical reduction of carbon dioxide, the copper surface exhibiting an increased PE total count tended to produce a greater amount of CH\({}_{4}\) as the reduction product [29]. The purpose of the present study is to clarify the TPPE characteristics of metallic copper samples mechanically abraded in alcohols, water, and air and ultrasonically cleaned in the liquids, and further, its relation to the properties of the liquids. We have already reported that two types of copper surfaces showed completely different TPPE behavior, but although it is of great interest, the reason why it occurs was not fully understood [26]. In this study, in view of the importance of the surface treatment of metallic copper, we tried to account for the mechanism of TPPE based on the acid-base interaction. First, we describe the important points of the TPPE method and briefly feature the present understanding of the TPPE results.