A Novel Vible-Light Photodetector Based on Chlorophyll-Modified ZnO Nanoparticles

Abstract

Abstract-This paper reports a new material for visible-light detection based on chlorophyll-modified ZnO nanoparticles. ZnO nanoparticles were synthesized via a hydrothermal process. Chlorophyll was extracted from Katuk (Sauropus androgynus) leaves, an Indonesian vegetable which has many benefits for health. ZnO nanopartcles were mixed with the extracted chlorophyll, later to be formed into a film onto ITO coated glass substrate by the casting method. The hybrid chlorophyll-modified ZnO nanoparticle film was characterized for its optical absorption and current-voltage (I-V) property. A visible-light response of the hybrid chlorophyll-modified ZnO nanoparticle film can be seen on the I-V curves as well as a dynamic response.ZnO is well known as an n-type semiconductor material with a wide band gap of 3.37eV, associated with an absorption characteristic in the UV range [1]. So much so that ZnO was often used as a UV detector [2], and in a variety of other applications (UV activated ZnO) such as gas sensor [3], in dye sensitized solar cells [4] and in photocatalytic degradation of dyes in wastewater [5]. Various attempts have been made to improve the characteristics of ZnO in sensor aplications by doping [6].On the other hand, it has been known that the chlorophyll is the green pigment that is partly responsible for the process of photosynthesis in plants. Some studies use chlorophyll as an active component in a hybrid organic-inorganic solar cell [7].The purpose of this research is expanding the range of applications of ZnO as a light detector, which in essence is a UV detector, to be a visible-light spectrum photodetector. Therefore the ZnO nanoparticle was modified with chlorophyll so that it might be sensitive to visible light. So far no one has done the modification of ZnO with chlorophyll for visible light sensor applications.ZnO nanoparticles were synthesized by the hydrothermal method using zinc acetate dihydrate dissolved in ethanol solution with the addition of ethylene glycol [8]. The solution was poured into a stainless steel autoclave and then treated hydrothermally at a temperature of 150°C for 6 hours, being stirred at a speed of 400rpm. The precipitate resulting from the * E-mail: akhiruddin@ipb.ac.id; maddu3@gmail.com hydrothermal process was washed 3 times with ethanol and then dried on a hotplate at a temperature of 100°C, subsequently calcined at 300°C in a furnace for 1 hour. The ZnO powder was analyzed by X-ray diffraction (XRD) with a scanning electron microscope (SEM) to investigate its structure and morphology.Chlorophyll is obtained from Katuk (Sauropus androgynus) leaves that have been extracted by using an organic solvent of 96% ethanol. The solution was filtered to obtain filtrate extract chlorophyll. To improve the stability of chlorophyll, the chlorophyll core of Mg is replaced by zinc (Zn). Firstly, degradation was performed by adding a solution of chlorophyll with 1M HCl dropwise until pH 4 was reached while stirring with a magnetic stirrer at a speed of 400rpm. The result of this s...

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