“…In 1957, Collatz and Sinogowitz [7] posed the problem of characterizing all singular graphs. The problem has received considerable attention in the literature (see, eg, [3‐5,10‐12,14‐21,24,26‐31,33] and references therein). In studying the above problem, some attentions are attracted to bound the nullity of a graph by using some of the structure parameters, such as the order, the matching number, the number of pendant vertices, and especially the maximum degree of the graph (see [5,6,8,12,14,15,17,22‐24,29,30] for details).…”