Carbon quantum dots (CQDs) are a class of carbon nanomaterials that have recently gained recognition as current entrants to traditional semiconductor quantum dots (QDs). CQDs have the desirable advantages of low toxicity, environmental friendliness, low cost, photostability, favorable charge transfer with enhanced electronic conductivity, and their comparable easy synthesis protocols. This article examines advancements in CQD research and development, with a focus on their synthesis, functionalization, and energy applications. Initially, various synthesis methods are discussed briefly with pros and cons. Herein, first top-down methods including arc discharge technique, laser ablation technique, plasma treatment, ultrasound synthesis technique, electrochemical technique, chemical exfoliation, and combustion were discussed briefly. The later section presents bottom-up (microwave synthesis, hydrothermal synthesis, thermal pyrolysis, and MOF template-assisted approach) and waste-derived CQDs synthesis methods. The next section is focused on the energy applications of CQDs including supercapacitors, lithium-ion batteries, photovoltaics, hydrogen (HER), and oxygen evolution reaction (OER). Finally, challenges and perspectives in this exciting and promising area are presented.

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Increasing population and industrial growth, combined with climate change, led to global water problems. This review paper summarizes the next-generation hybrid graphene-based membrane materials that are used for water purification to meet global freshwater supplies. Graphene-based membrane materials are believed to be the advanced materials for the desalination process because of their atomic thickness and tunable functionalities. The effect of membrane fabrication techniques and operating conditions on the separation and membrane fouling mechanisms are discussed in depth. The present study discusses the development, advantages, and shortcomings of using hybrid graphene membranes compared to traditional polymeric membranes. To extend the applications of graphene membranes, more attention should be paid to the water permeability and membrane selectivity in long-term operation at conditions similar to those in the field for performance analysis. While literature reviews have mainly concerned the ability of graphene materials to adsorb water contaminants, there is very limited updated information related to its sieving properties. Moreover, the literature lacks a comparative discussion of graphene-based membranes with other hybrid membrane materials. Thus, a profound understanding of graphene-based membranes is much needed to unlock the potential for graphene materials. Also, research interest in the preparation of the hybrid graphene membrane is expected to be explored in the future.

Organic fouling in the forward osmosis process is complex and influenced by different parameters in the forward osmosis such as type of feed and draw solution, operating conditions, and type of membrane. In this article, we reviewed organic fouling in the forward osmosis by focusing on wastewater treatment applications. Model organic foulants used in the forward osmosis literature were highlighted, which were followed by the characteristics of organic foulants when real wastewater was used as feed solution. The various physical and chemical cleaning protocols for the organic fouled membrane are also discussed. The study also highlighted the effective pre-treatment strategies that are effective in reducing the impact of organic fouling on the forward osmosis (FO) membrane. The efficiency of cleaning methods for the removal of organic fouling in the FO process was investigated, including recommendations on future cleaning technologies such as Ultraviolet and Ultrasound. Generally, a combination of physical and chemical cleaning is the best for restoring the water flux in the FO process.

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