Nanosensors of Fluorescent Carbon Quantum Dots Derived from Banana Peel: Application in Sr2+ and Co2+ Detection

Research Article

Austin J Biosens & Bioelectron. 2022; 7(1): 1041.

Nanosensors of Fluorescent Carbon Quantum Dots Derived from Banana Peel: Application in Sr2+ and Co2+ Detection

Kaffash M¹, Bakhtparvar A¹, Rezvani-Noghani A¹, Hosseini S², Mokaberi P¹ and Chamani J¹*

1Department of Biology, Faculty of Sciences, Mashhad Branch, Islamic Azad University, Mashhad, Iran

2Cancer Research center, Mashhad University of Medical Sciences, Mashhad, Iran

*Corresponding author: Jamshidkhan Chamani, Department of Biology, Faculty of Sciences, Mashhad Branch, Islamic Azad University, Mashhad, Iran

Received: October 20, 2022; Accepted: November 19, 2022; Published: November 26, 2022

Abstract

Natural Carbon Quantum Dots (NCQDs) are known to contain photo luminescence property and stand as a promising nanomaterial group. Therefore, we intended to generate an intelligible and effective hydrothermal procedure for performing the green synthesis of this material through the usage of banana peel waste as a feasible and durable natural carbon source. The obtained NCQDs were characterized by the means of UV-visible absorption spectroscopy, spectrofluorometry, Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD), zeta potential, Atomic Force Microscopy (AFM), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and Thermo Gravimetric Analysis (TGA). The lack of utilizing any toxic substances has guaranteed the safety of this procedure in all the biological practices. Therefore, the high crystalline and spherical morphology of synthesized NCQDS with an average roughness of about 5.9 nm were indicated by the results of TEM and XRD. We also observed a high water stability and solubility due to the presence of hydroxyl and carboxyl group and excitation- dependent emission performance with the satisfying quantum yield of 12 %. The zeta potential of prepared NCQDs reached up to -27.4 mV. Furthermore, in order to determine the low toxicity and favorable biocompatibility of this product, we studied the toxic effects of NCQDs on the fibroblast cell line of a normal mouse through the MTT assay. In conformity with the gathered data, these NCQDs contain the potential of being utilized as a nontoxic carrier and a fine alternative for bio-sensor, bio-imaging, and drug delivery applications. The development of these NCQDs was completed with the objective of acting as a highly sensitive fluorescent “on-off-on” switch sensor in the course of the selective and simultaneous sensing of Sr2+ and Co2+. Fluorescence data revealed that the binding constants of Sr2+ and Co2+ to NCQDs were to be 1.39 × 104 M-1 and 1.58 × 104 M-1 respectively. The observations were indicative of a linear relationship among the Sr2+ and Co2+ ions volume and the fluorescence intensity throughout the range of 0 to 0.1 mM.

Keywords: CQDs; Banana peel; Hydrothermal; Spectroscopy; FESEM; MTT assay; Sensor

Introduction

Being the most proponent fluorescent nanoparticles, the application of Semiconductor quantum dots can be vastly detected as nanoprobe throughout the fields of sensing and bio-imaging due to containing distinctive optical qualities [16,26]. In spite of this fact, the concern for the toxicity of this substance to the health of humans and environment, caused by the existing heavy metal constituents in its structure, is gradually increasing [8]. The very first signs of carbon quantum dots discovery was reported in 2004 in the course of purifying single-walled carbon nano-tubes by the means of preparative electrophoresis [51]. Standing as a new category of fluorescent small carbon nanoparticles, Semiconductor quantum dots were considered as a replacement for carbon quantum dots due to containing an ultrafine smaller size, biocompatibility, super hydrophobicity, excellent photo luminescent properties, low cytotoxicity, and high chemical reliability [2,31]. The NCQDs can be applicable for substituting semiconductor QDs and organic fluorescent dyes for science applications.In addition, considering their certain features, this product can be applied in several applications of various areas such as bio-imaging, sensing, photo catalysis, drug delivery, cancer therapy, and etc [11,12,22,27,33,40,46,48,50,52,53,]. There are two principal methods in general for synthesizing NCQDs that include top-down and bottom-up routes. The cases of top-down methods for synthesizing CQDs involve the usage of different bases such as graphite, carbon fibers, coal, soot and biomass, which are performed through schematic treatments including arc-discharge, laser ablation, electrochemical oxidation, chemical oxidation, ultrasonic treatment, and solvothermal procedures [10,13,15,20,25,29,39,44,47]. On the other hand, the bottom-up approaches involve the synthesis of NCQDs by the exertion of precursors similar to folicacid, gelation, citric acid, and organic sources that include potato, grapefruit, watermelon, peanut shells, and pineapple [19,23,30,38,41]. The benefits of exerting plants for the fabrication of nano-particles have become evident by recent reports, which include their simple availability, safe handling, and being biodegradable. Furthermore, the usage of these waste sources for synthesizing purposes results in the reduction of pollution and also helps in cleaning up the environment from these waste materials [39,45]. Apparently, the fluorescence functionality of NCQDs can be improved through a more enhanced doping of hetero-atoms into the carbonaceous framework and surface passivation and furthermore, more qualified CQDs can be obtained facilely through the concurrent proceeding of hetero element doping and passivation [1,23]. Due to accommodating multifarious hetero-atoms, the simple synthesis of CQDs by natural substances results in the production of products that contain varying surface groups along with distinctive features without performing any passivation or modification. Consequently, many investigations have attempted to succeed in synthesizing CQDs by the usage of different natural biomass/bio-waste [6,32]. In bottom-up approaches, the synthesis of CQDs is performed through microwave irradiation, hydrothermal-solvothermal treatment, hydrothermal method, and plasma [9,36,41]. Standing as the most effective and facile technique, hydrothermal method functions on water system and can provide simple manipulation, un expensive apparatus, and fine selectivity on water system [43]. This method has been exerted by many researchers such as Arumugam Selva Sharma and co-workers, which performed the synthesis of CQDs and achieved a size of 2-4 nm by the usage of soy milk. Also, Sun and co-workers reported the synthesis of CQDs from selenicerusgr and if lours through the hydrothermal method while lacking the exertion of any additional oxidizing agents such as ethanol [4,43]. In this work, an uncomplicated, cheap, and applicable procedure for performing the synthesis of NCQDs by the usage of banana peel through green and facile hydrothermal method is introduced, which lacks the requirement of any chemical materials and was followed by characterizing the obtained product using different analytical techniques. The resulted NCQDs possess bright fluorescence and satisfying stability, as well as a quantum yield of 7.5 %. The results of Raman spectroscopy (D/G ratio of 0.85) indicated the purity of our synthesized NCQDs, while this fluorescent product was observed to contain a spherical shape with the average diameter of 5.9±0.14 nm. Considering their physicochemical features, the high potent of NCQDs as a promising product for mass scale manufacturing, bio-sensor, bio-imaging, and other biological implementations is undeniable.

Material and Methods

Materials

Banana was purchased from a local market in Mashhad, Iran. Sodium hydrogen carbonate and EDTA were obtained from Merck chemicals. All solvents were analytical grade and used without further purification. Millipore was used throughout the study.

Preparation of NCQDs

These biocompatible NCQDs were synthesized from banana peel waste via an innovative method, first we gathered some banana peels and dried them in the sunlight, 3gr of obtained brown powder were added into 100 ml deionized water. This suspension was boiled and stirred at 70°C for 2h. After 2h, the upper liquid of the obtained solution were transferred into Teflon lined stainless steel autoclave. The autoclave was tightly sealed then placed into the oven at 150°C for 4h. Then, it had cooled to room temperature, the upper liquid were centrifuged at 8317.6 rcf (8000 rpm. min) for 10 minutes. Next, the obtained liquid passed through filter paper and the obtained light liquid were filtered with 0.22m filter to remove the large substances. For dispersing of the synthesized NCQDs, was done for 30 minutes. The obtained liquid was natural carbon quantum dot solution. A part of NCQDs was kept for UV-visible and PL spectra and the other part of liquid was dialyzed (MW=35 kD) for about 24h (Figure 1).