## 1 Introduction  
In recent years, photocatalysts have attracted much attention due to their wide range of applications, from generating hydrogen by splitting water to decomposing organic contaminants in wastewater [1]. In the decomposition of organic contaminants such as dyes in wastewater, the photocatalyst uses visible light or ultraviolet (UV) light as an irradiating source to mineralize the contaminants in order to produce the end products such as carbon dioxide and water. TiO\({}_{2}\) has been the subject of early study in photocatalytic materials. However, due to its wide band gap, it can only work under ultraviolet irradiation for photocatalytic activation, which leads to very low energy efficiency in utilizing solar light. This is because UV light is only utilizing 5% solar energy, a small fraction compared to visible light, which is 45% [2]. Therefore, research has been focused on finding a method or materials that can work efficiently under visible light irradiation.  
Among the widely studied materials are bismuth-based photocatalysts, which have been proven to be suitable in the degradation of organic contaminants under visible light irradiation [3]. This is because bismuth compound such as Bi\({}_{2}\)O\({}_{3}\), BiVO\({}_{4}\), NaBiO\({}_{3}\) has a band gap range less than 3.0 eV and is environmentally friendly. Various approaches in synthesizing BiVO\({}_{4}\) have been reported. A monoclinic BiVO4 has successfully been prepared by solid state reaction (SSR) and by melting at a high temperature [4], whereas, a tetragonal BiVO4 has been synthesized by a precipitation method at a room temperature [5]. In addition, a simple aqueous process in preparing both monoclinic and tetragonal phase was also reported [6]. In addition, the use of hydrothermal process in creating various structural, morphologies and phase were also being reported. Since BiVO\({}_{4}\) can be prepared by using a simple method, it is one of the suitable candidates in the study of a low-cost synthesis method [7].  
Besides that, nano-size photocatalytic materials have been proven to have a high degradation rate in degrading organic contaminants, due to their having a greater surface area, which provides more fine contact among catalyst particles and organic substrate, good dispersion, and abundant active sites. However, the recovery process becomes a drawback for this nano-size photocatalyst, since the powder-like nano-photocatalyst often suffers from deactivation, agglomeration, and difficulty settling for recycling after the initial run. This makes it hard to recycle the photocatalyst, and nonrecyclable photocatalytic materials will increase operating cost, which significantly limits their application in wastewater treatment. In most wastewater treatment, photocatalysts are suspended in aqueous solution. Separation of photocatalysts must be done by settling with the aid of gravity or mechanical centrifugation. Settling of ultrafine photocatalyst particles with the aid of gravity has been commonly observed to proceed very slowly.  
Therefore, in this study, we developed a microstructure photocatalyst composed of nanosheets to enhance the process by using a simple, low-cost method that results in the formation of a flower-like bismuth vanadate microstructure that has a greater surface area, more stability, and higher efficiency in organic dye degradation under visible light irradiation. As for the dye contaminant, we chose methylene blue (MB) dye because it is a frequently used industrial dye. MB dye has the chemical structure of C\({}_{16}\)H\({}_{18}\)N\({}_{3}\)SCI and is shown in Figure 1.