1. A method for increasing gas selection functions of a multifunctional gas sensor, comprising: forming a noble metal nanoparticle modification layer on a surface of a semiconductor gas-sensitive material layer of a probe of a gas sensor, such that a single probe of the gas sensor is capable of implementing selectively detection of at least three gases in an operating temperature range of 0-400° C.; wherein the noble metal nanoparticles are gold nanoparticles, a thickness of the noble metal nanoparticle modification layer is 1-10 nm, the at least three gases comprise formaldehyde, ethanol and acetone;

wherein the selectively detection of at least three gases in the operating temperature range of 0-400° C. comprises: selectively detecting formaldehyde, ethanol and acetone by using characteristics of a highest response to a certain gas at different operating temperatures by the gas sensor, the characteristics including a highest response to formaldehyde at an operating temperature below 200° C. by the gas sensor, a highest response to ethanol at an operating temperature between 200° C. and 340° C. by the gas sensor and a highest response to acetone at an operating temperature range of 400° C. by the gas sensor; and

wherein the noble metal nanoparticle modification layer is prepared using any of following methods:

(1) depositing a 1-10 nm noble metal film on the surface of the semiconductor gas-sensitive material layer by using magnetic sputtering, and rapidly annealing at high temperature to form split noble metal nanoparticles, thereby obtaining the noble metal nanoparticle modification layer; or,

(2) soaking the probe of the gas sensor coated with the semiconductor gas-sensitive material layer in an ethanol suspension of the noble metal nanoparticles for at least 10 hours to allowing the noble metal nanoparticles to self-assemble onto the surface of the semiconductor gas-sensitive material layer, and heating to remove water and organic matter, thereby obtaining the noble metal nanoparticle modification layer; wherein the semiconductor gas-sensitive material is zinc oxide nanotetrapods.