Bounds for the energy of graphs

The energy of a graph G, denoted by E(G), is the sum of the absolutevalues of all eigenvalues of G. In this paper we present some lowerand upper bounds for E(G) in terms of number of vertices, numberof edges, and determinant of the adjacency matrix. Our lower boundis better than the classical McClelland’s lower bound. In addition,Nordhaus–Gaddum type results for E(G) are established.