Rare-earth long afterglow luminescent powder, preparation method of luminescent powder and method applying luminescent powder as hidden fingerprint emergence reagent

The invention discloses rare-earth long afterglow luminescent powder, a preparation method of the luminescent powder and a method applying the luminescent powder as a hidden fingerprint emergence reagent. The general structural formula of the rare-earth long afterglow luminescent powder is M2MgSi2O7:0.02Eu2+, 0.04Dy3+, wherein M refers to one or two of Sr and Ca; and the particle size of the rare-earth long afterglow luminescent powder is 1-3 microns. The rare-earth long afterglow luminescent powder is prepared by virtue of a high-temperature solid-phase method. The method applying the luminescent powder as the hidden fingerprint emergence reagent comprises the following steps: mixing the rare-earth long afterglow luminescent powder with reduced iron powder, emerging a hidden fingerprint on an object by virtue of the compound, acquiring the fingerprint image by virtue of white light or ultraviolet excitation, or acquiring the self-luminous image. The preparation method is simple, the excited wavelength of the prepared rare-earth long afterglow luminescent powder is wide in range, the emission wavelength peak value of the long afterglow powder can change between 466nm and 533nm by regulating the Sr/Ca ratio, and the field hidden fingerprint emergence is conveniently realized. The rare-earth long afterglow luminescent powder has high fluorescence intensity and long afterglow (self-luminous) characteristics, and the background interference of the object can be effectively eliminated after fingerprint emergence; and moreover, the luminescent powder is non-toxic, nondestructive and environment-friendly.