Ehsan Hosseini

Graphene quantum dot (GQD) is one of the youngest superstars of the carbon family. Since its emergence in 2008, GQD has attracted a great deal of attention due to its unique optoelectrical properties. Non‐zero bandgap, the ability to accommodate functional groups and dopants, excellent dispersibility, highly tunable properties, and biocompatibility are among the most important characteristics of GQDs. To date, GQDs have displayed significant momentum in numerous fields such as energy devices, catalysis, sensing, photodynamic and photothermal therapy, drug delivery, and bioimaging. As this field is rapidly evolving, there is a strong need to identify the emerging challenges of GQDs in recent advances, mainly because some novel applications and numerous innovations on the ease of synthesis of GQDs are not systematically reviewed in earlier studies. This feature article provides a comparative and balanced discussion of recent advances in synthesis, properties, and applications of GQDs. Besides, current challenges and future prospects of these emerging carbon‐based nanomaterials are also highlighted. The outlook provided in this review points out that the future of GQD research is boundless, particularly if upcoming studies focus on the ease of purification and eco‐friendly synthesis along with improving the photoluminescence quantum yield and production yield of GQDs.

Transparent electromagnetic interference (EMI) shields are increasingly in demand for medical, military, wireless net-works, aerospace electronics and navigation control systems. To date, studies have mixed pristine and/or doped con-ductive polymers with carbon allotropes and metallic fillers to increase the total shielding effectiveness, compromising the transparency, amount of the material used and weight of the shields. Obtaining cost-effective and transparent EMI shields without the need to incorporate fillers is extremely desirable. Herein, we implement a design strategy for fabri-cating a gigahertz (GHz) highly transparent shield made of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). A total EMI shielding effectiveness of 15 dB is achieved in the X-band frequency range for a 50 nm ultra-thin film with a high transparency of 97.1%. The fabricated filler-free EMI shield holds a record thickness-specific shield-ing figure-of-merit of 300 dB/µm – far exceeding the best values for micron-thick silver-based, as well as carbon- and MXene-based composite materials shields – with even a higher transparency. The feasibility of the developed filler-free shield for large-scale applications is validated by its integration into a cell phone display glass, as a prototype, in which the EMI shielding effectiveness elevates to 18.3 dB.

The high conductivity of initially solvent-doped poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) thin films is reduced unexpectedly upon immersion in sulfuric acid, forming a new morphology type introduced as a “patchy” grain morphology. Correlating the intra-grain structural parameters and grain morphology via spectroscopy and atomic force microscopy quantification and using a comprehensive 3D crystalline structural model, it is revealed that the slow PEDOT interchain charge transport, dictated by the π–π stacking distance and abundance within each grain, is the primary factor controlling the overall conductivity, while the grain morphology has a weaker influence.