No abstract

Tea, from the old ages to the day, is widely consumed both for enjoyment and health care due to its positive effects. The consumption of these products is increasing day by day as a result of the clear presentation of the fact that tea contains high amount of antioxidant substances (such as phenolic compounds), which is important in prevention and treatment of diseases. Tea beverage is a very important source of polyphenols. In this study, phenolic content and antioxidant capacity of different tea species were calculated by modeling with experimental design method. In the experimental part, polyphenol content was determined using the Folin-Ciocalteu method. The total amount of phenolic substance content was examined by Box-Behnken design and response surface method on black tea, green tea and white tea on different extraction temperature, extraction time and solid / liquid ratio. Solid / liquid ratio was found to be the most important parameter in terms of polyphenol content extraction from different tea samples. The highest polyphenol amount (411.762 mg gallic acid / mL) was found in green tea. To the best of our knowledge, this is the first data presenting comparatively study the effect of extraction condition on amounts of phenolic compounds from different tea samples.

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In this study, copper oxide nanoparticles (CuO-NPs) were obtained by biosynthesis using aqueous extracts of black tea (BT), green tea (GT) and tarragon tea (TT). The effect of extracts from leaves of plants on the reduction mechanism has been investigated. The amount of polyphenol as using reducing agent in the extracts from the plants was determined according to the Folin-Ciocalteu's method. Total phenolic acid amounts of the extracts of BT, GT and TT were found as 59.18, 42.81 and 49.83 mg/L, respectively. Properties of synthesized CuO-NPs using these extracts were examined by UV-visible spectroscopy, Fourier infrared transformation spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX) and Atomic Force Microscopy (AFM) analysis. In addition, prepared CuO-NPs were used in methylene blue (MB) removal as a photocatalyst. According to AFM results, average size of CuO-NPs was determined ranging from 10 to 12 nm. Regarding photocatalytic activity, prepared CuO-NPs from BT, GT and TT removed 89%, 87% and 90% of dye in 360 min, respectively. In the photocatalytic removal study, the reaction kinetics were investigated with zero, first and second order kinetics. Bu çalışmada, bakır oksit nanopartiküller (CuO-NP'ler), siyah çay (BT), yeşil çay (GT) ve tarhun çayı (TT) sulu ekstraktları kullanılarak biyosentez yoluyla elde edildi. Bitkilerin yapraklarından elde edilen ekstrelerin indirgeme mekanizmasına etkisi araştırılmıştır. Bitkilerden elde edilen ekstraktlarda indirgeyici ajan olarak kullanılan polifenol miktarıFolin-Ciocalteu'nun yöntemine göre belirlendi. BT, GT ve TT ekstrelerinin toplam fenolik asit miktarları sırasıyla 59.18, 42.81 ve 49.83 mg/L olarak bulundu. Bu özütler kullanılarak sentezlenen CuO-NP'lerin özellikleri UV-görünür spektroskopi, Fourier kızılötesi dönüşüm spektroskopisi (FTIR), Taramalı Elektron Mikroskobu (SEM), Enerji Dağıtıcı X-ışını spektroskopisi (EDX) ve Atomik Kuvvet Mikroskobu (AFM) analizi ile incelenmiştir. Ayrıca hazırlanan CuO-NP'ler metilen mavisi (MB) gideriminde fotokatalizör olarak kullanılmıştır. AFM sonuçlarına göre, CuO-NP'lerin ortalama boyutu 10 ila 12 nm arasında belirlendi. Fotokatalitik aktivite ile ilgili olarak, BT, GT ve TT'den hazırlanan CuO-NP'ler sırasıyla 360 dk. da % 89, % 87 ve %90 oranında boyayı giderdi. Fotokatalitik giderim çalışmasında reaksiyon kinetiği sıfır, birinci ve ikinci dereceden kinetik ile incelendi.

Graphene is an important material that has attracted attention in recent years due to its large surface area, mechanical strength, thermal, electrical and magnetic properties. In this work, reduced graphene oxide (RGO) was obtained by reducing the graphene oxide (GO) with green synthesis. For this purpose, white cabbage aqueous extract was selected to reduce GO. The total phenolic acids, which are the reducing agent in the extract, were determined according to the Folin-Cioceltau method. It was determined that there is 0.064 grams of polyphenols in 1 mL of white cabbage extract. In order to determine the reduction experimental conditions, a reduction temperature of 25, 50 and 100 ⁰C and 1, 2, 4 and 6 hours of reduction time were studied. Structural characterization of synthesized RGOs was performed with XRD, FTIR and SEM techniques. The results showed that GO was reduced at a reduction reaction temperature of 100 °C and a reduction reaction time of 6 hours. The peak seen at 22.08⁰ in the XRD data is evidence of reduction of GO.