A guitar interface device for a digital guitar system is adapted to receive digital signals, convert those signals into analog signals, and output the analog signals, so that the digital guitar system may be utilized with conventional analog equipment. The second portion of the driven balance shaft is constructed to produce a moment of inertia less than a moment of inertia that is produced in the first portion of the drive balance shaft. The present invention has the advantages of simple preparation process, and film thickness controllable at nanoscale precision; the invention also achieves the immobilization of luminescent polymer via restricted space among LDHs layers and host-guest interaction, effectively improves thermal stability, and reduces fluorescence quenching caused by aggregation.