## 1 Introduction  
Hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)) is one of the products during enzyme catalyzing, such as glucose oxidase, which is closely related to diverse physiological and pathological consequences including aging, organ injury and cancer, has received enormous attentions in academy and industry [1; 2; 3; 4; 5; 6]. There is great need to detect H\({}_{2}\)O\({}_{2}\) in environmental, industrial and clinic fields [7]. Thus, it is critical to develop a novel method for the accurate and quick detection of H\({}_{2}\)O\({}_{2}\). During the past few decades, many techniques have been established to detect H\({}_{2}\)O\({}_{2}\), such as fluorimetry [8], titrimetry [9], chemiluminescence [10], spectrophotometry [11], chromatography [12], colorimetry [13], electron spin resonance spectroscopy [14], electrochemical methods [15; 16], and so on. Among these techniques, electrochemical methods have attracted wide attention for real-time detection of H\({}_{2}\)O\({}_{2}\) because of their high sensitivity, fast response and low cost. At present, the electrochemical sensors used for detection of H\({}_{2}\)O\({}_{2}\) are mainly classified into enzymatic and nonenzymatic sensors. Compared to enzymatic sensors, the nonenzymatic sensors composed of transition metal nanoparticles (NPs), such as Pt, Ag, Au, Ni, etc., have generated a great deal of interest, thanks to their outstanding long-term stability/sensitivity regardless of the intrinsic nature of enzymes [17; 18; 19; 20].  
Carbon-based materials, such as graphene and carbon nanotubes, have become a hot spot in many research fields [20; 21]. Graphene is a two-dimensional material with a layer of sp\({}^{2}\) C atoms tightly packed into a honeycomb lattice. It possesses extraordinary mechanical, thermal and electronic properties [22; 23]. Moreover, the large surface area and good electronic properties of graphene are considered advantages of an alternative electrode material for sensors [24; 25]. Until now, several methods have been used to synthesize graphene, such as chemical vapor deposition [26], electrochemical exfoliation [27], micromechanical exfoliation [22], thermal growth from silicon carbide [28], etc. Among these methods, a solution-based method is thought to be the most promising route to produce large quantities of graphene [29]. Graphene oxide (GO) can be reduced by different methods, including chemical [30; 31; 32], thermal [33], electrochemical [34; 35; 36] and microwave-assisted techniques [37; 38]. So far, GO can be manufactured into free-standing reduced graphene oxide paper (rGOP), with thicknesses ranging from 1 to 30 \(\upmu\)m [39]. Such rGOPs have preferable extension and tensile properties (32 GPa) compared to graphite foils, bulky papers and other paper-like materials [39]. The combination of the superior mechanical strength, high electrical conductivity (7200 S m\({}^{-1}\)), thermal stability, structural uniformity and biocompatibility enables rGOP to be an ideal material for many technological applications [40; 41].  
In this article, we report a nonenzymatic biosensor based on free-standing reduced graphene oxide paper modified with Pt nanoparticles (PtNPs). Free-standing reduced graphene oxide paper could be an alternative to the traditional glassy carbon electrode, as the substrate for detection of H\({}_{2}\)O\({}_{2}\). The schematic illustration of the fabrication process for a Pt/rGOP electrode is shown in Figure 1. Test results reveal that electrodeposition of PtNPs on free-standing reduced graphene oxide paper has two good linear responses to H\({}_{2}\)O\({}_{2}\), ranging from 0.2 \(\upmu\)mol/L to 8.5 mmol/L, with a detection limit of 100 nmol/L (S/N = 3). The as-prepared flexible and free-standing reduced graphene oxide paper has great potential in real applications, especially for biosensor and point-of-care medical devices.