نشریه مطالعات در دنیای رنگ
سال دوازدهم شماره 2 (پیاپی 45، تابستان 1401)

Organic light emitting diodes containing organic materials and components creat a bright vision in the development of displays and lighting technology due to the reduction of costs, the facility of the production process, and the production process due to the elimination of noble heavy metals. Today, much research is being done on developing high-efficiency of the organic emitter. For this purpose and design of effective material, it is necessary to pay attention to two points: 1) how to overcome the efficiency limit caused by the number of spin-excitons and 2) how to increase the efficiency of out-coupling. Metal-free compounds usable in organic light emitting diodes are classified into two general classes, small molecule compounds and dendrimers. Various emitter compounds are synthesized from these classes and evaluated for use in the structure of OLED. This article reviews metal-free organic emitters for use in Organic light emitting diodes.

Nowadays, the photocatalytic process, one of the advanced oxidation methods for removing environmental pollutants, has attracted tremendous research interest. The piezo-photocatalytic effect has been proposed as one of the most effective methods to improve photocatalytic activity to increase the efficiency and effectiveness of advanced oxidation methods. Many recent efforts have been made in dye wastewater treatment using photocatalytic compounds. However, few studies have suggested using piezocatalytic properties to improve the photocatalytic performance of materials (piezo-photocatalysts). This study reviews compounds' photocatalytic, piezocatalytic, and piezo-photocatalytic properties with these properties and their potential in removing dyes from wastewater. Also, considering the literature, the approaches to increase the performance of photocatalysts and advanced applications of piezocatalysts and piezo-photocatalysts have been presented. Finally, piezo-photocatalyst has been introduced as the best approach to remove dyes from wastewater. Piezo-photocatalytic dye decomposition shows the piezoelectric efficiency in developing the piezocatalytic process. This process can promote the separation of photo-induced electron-hole pairs and lead to the synergistic effect between photocatalytic and piezocatalytic properties.

In recent years, </em>compared to chemical and physical methods, the biosynthesis of metal nanoparticles has been of interest to many researchers due to its easy, clean, cheap, accessible, and biocompatible preparation process. Different parts of plants such as leaves, roots, stems, flowers, fruits, seeds, skin, and waste contain various compounds such as polyphenols, flavonoids, tannins, alkaloids, sugars, carbohydrates, proteins, and terpenoids, which are used for the biosynthesis of nanoparticles. The efficiency of nanoparticle synthesis, their amount, shape, and size depend on compounds' reducing and stabilizing power in plant extracts. The main role of biological compounds is the reduction of metal ions and their conversion to metal (M°), as well as stabilization by creating a protective layer on the synthesized nanoparticles to prevent their accumulation. In this review paper, recent advances in synthesizing silver nanoparticles and their coating on textiles using different parts of plants in two general methods, in situ and ex situ, have been reviewed. Factors affecting silver nanoparticles' efficiency, shape, and size, such as metal precursor concentration, plant extract concentration, temperature, etc., have been reviewed and summarized. In addition, the multifunctional properties of textiles coated with silver nanoparticles, such as color properties, antibacterial, antifungal, antioxidant, ultraviolet protection, etc., have also been discussed.

• The first generation of quantum dots was synthesized based on inorganic materials and was so harmful to human beings, animals, and organisms. Therefore, the researchers synthesized and investigated a new generation of fluorescent materials named carbon quantum dots. They have more fluorescence intensity and no harmful effects on any living. Carbon quantum dots are a type of fluorescent material with a size between 2 to 10 nm. They can be synthesized using different synthesis methods like hydrothermal, microwave-assisted, synthesis simple heating using reflux, pyrolysis, carbonization, and other synthesizing methods via two different synthesizing approaches named top-down method and bottom-up method. These materials can be used in different applications like bioimaging, biosensors, drug delivery systems, solar cells, LEDs, chemical sensors, etc. Another important application of these nanomaterials is using them as anti-counterfeiting inks for security reasons like security printings, and bank-related documents like cheques, etc. This paper will briefly look at carbon quantum dots, the synthesis methods, and their applications.

Condensation may occur during various industrial applications, including water collection, desalination, energy generation, and thermal management. This phenomenon affects heat transfer efficiency during energy generation and heat management processes. Film-wise and dropwise condensation were the two types of condensation based on their formation manner. Condenser tubes are one of the energy conversion systems in which the condensation phenomenon dramatically affects the system's efficiency. The high surface energy of the condenser tube results in water film formation on the tube surface, which hinders heat transfer. Therefore, the heat transfer efficiency of the condenser is reduced due to further energy loss. The film-wise condensation should be altered to dropwise ones by reducing the surface energy of the tube to eliminate this issue. Hence, different coatings are applied to increase the condenser tubes' hydrophobicity and heat transfer capacity. In this study, the importance of wettability and heat transfer mechanisms in condenser tubes was determined primarily. Afterward, different coatings used to create dropwise condensation were introduced. Eventually, the applications and attributes of the mentioned coatings based on their cost, strength, durability, and efficiency were introduced.

One of the main problems of the paint and ink industry is the dispersion of carbon black in water-based media. Surface modification of the particles was used as an effective method to overcome the problem. Diazotized sulfanilic acid was used to modify the carbon black surface as the modifier. Due to the diversity of effective parameters and vast levels, the RSM method was used to find a suitable range of the parameters (temperature, modifier amount, ultrasonic time, and pH) at 5 levels. The properties of the modified pigment were analyzed by DLS, TGA/DTG, and FT-IR. Also, the accuracy of the modification was confirmed. Optimum conditions for modification were pH = 3.66, temperatures around 25 ℃, ultrasonic time of 30 minutes, and 6.25 mmol of the modifier. The optimally modified sample showed very high dispersion stability, so this sample has remained dispersed and stable for more than 8 months without any precipitation.