Surface-enhanced Raman scattering (SERS) has become one of the most attractive and powerful spectroscopic techniques for label-free ultrasensitive detection of chemical and biological species. Each molecule has a unique Raman spectral fingerprint. references. [1,2,3] SERS can effectively enhance its Raman signal and currently plays an important role in various fields such as medical diagnosis, environmental and safety applications. However, the quality of the SERS substrate determines the degree of SERS signal enhancement. Many SERS substrate preparation methods have been reported and available, including electron beam lithography, chemical vapor deposition, nanoparticle (NP) deposition, and self-assembled NPs [4,5,6,7]. They exhibit excellent detection performance, but large-scale preparation always results in a laborious and rather expensive process. In recent years, paper-based SERS substrates have received widespread attention.Their advantages are that they are cheap; flow easily; are biodegradable, disposable and lightweight; and are widely used [8,9,10,11]. Considerable research has been conducted on impregnating metal nanoparticles into paper using various processes such as dip coating, inkjet printing, screen printing, and physical vapor deposition. [10,12,13,14].Hongkong [15] and colleagues reported a SERS substrate. They applied an imidazole molecular sieve framework layer to gold nanoparticle-impregnated paper prepared by a dry plasma reduction method. 4-Thioacetaldehyde was used as a probe molecule. Enhancement factor (EF) is 1.0×106. These processes require more time-consuming dipping of paper into concentrated nanoparticles.handsome [16] Gold nanostars were immobilized on filter paper to make SERS substrates. They used crystal violet as a Raman probe molecule. EF is 1.2×107. But this method requires early processing of the filter paper. The processing steps are complex and time-consuming.Jun [17] Using 4-aminothiophene as the Raman probe molecule, Ag NPs were immobilized on polyurethane (PU) sponge as the SERS substrate. EF reports 2.67 × 106. This flexible substrate improves sample collection efficiency. However, the production process of SERS substrates is complicated.Pushkaraj [18] Use 2D SERS-active silver nanowire networks to solve the matrix storage problem by combining NPs with hydrogels.in this task [19], used 3D printing technology to prepare low-cost, high-sensitivity SERS templates, thus proving that 3D printing technology can be used to produce reproducible SERS patterns and SERS arrays. Russell et al. [20] reported a pen that can write on paper in flexible electronic devices. L. Polavarapu studied a paper-and-pencil (POP) method to fabricate SERS substrates.The SERS performance of plasmonic paper substrates prepared with three different types of nanoparticles at three different excitation wavelengths was studied. [21].
In this work, we prepared silver (Ag) NP gel pens and successfully demonstrated that they are good SERS devices.Because silver nanoparticles have a higher extinction cross section than gold nanoparticles [22], they usually have higher SERS efficiency. Therefore, we choose Ag NPs as the filling material of the silver gel pen. However, Ag NPs have strong chemical activity and are easily oxidized in air. We improved the silver gel pen to effectively protect Ag NPs. We then looked at several paper-based materials commonly used in the laboratory, tested a variety of paper platforms, and analyzed the specifics of how this approach affects Raman intensity during substrate preparation. The SERS substrate is made directly on the paper substrate using a silver glue pen. [23]. This method is convenient, fast, and has better enhancement effect than the traditional laboratory capillary injection method.
In this work, R6G was selected as the probe molecule for SERS analysis. The SERS immersion method was used to determine the amount of R6G, which is a highly efficient probe molecule commonly used in Raman spectroscopy enhanced measurements. The limit of detection (LoD) of R6G is 98.4 fmol/L, and the EF of the paper-based SERS substrate is calculated to be 8.2 × 108 For R6G. In addition, the substrates were characterized by scanning electron microscopy (SEM). Insecticides and methyl parathion are common pesticides used in apple cultivation. They are harmful to humans and can easily remain on the surface of the fruit. [20]. On this Raman detection platform, we detected pesticide residues on fruit skins at a concentration of 10−8 mol/L Insecticide pesticide residue. In this method, the preserved Ag NPs gel is cheap, simple to make, has good enhancement effect, and can be applied to the detection of low-concentration samples.