New Horizons in the Synthesis, Properties, and Applications of MXene Quantum Dots

Abstract

soum led the discovery of a new class of materials called MXene which was synthesized by selective etching of MAX phases. Here, a few layered arrays of (early) transition metal atoms are connected by a carbon/ nitrogen atom layer, linking the metallic layer known as transition metal carbides/nitrides or carbonitrides. [9,10] The general formula of MXene is M (n+1) X (n) T (x) or MAX; where M represents transition metal ions (such as Ti, Sc, Nb, and Mo), X represents Carbon or Nitrogen element, and T is any surface functional group such as Oxygen, Fluorine, or Hydroxyl group. Such compounds show an exceptional fusion of electronic conductivity and optical properties arising from the free electrons of the transition metal carbides or nitrides along with hydrophilicity from the surface functional groups. [11][12][13][14][15] The steady 2D forms of MXenes display distinguishing properties unlike the intralayer covalent bonds and weak van der Waals interactions seen in the bulk material. They possess a typical planar morphology with alterable surface characteristics, excellent conductivity, and hydrophilicity as well as appreciable thermal, mechanical, optical, and chemical properties. MXenes also have profound applications in energy-related devices, electrochemical and fluorescent detection, water purification, catalysis, and environmental research. [13,16,17] Interestingly, the etching of the MXene layers results in the formation of 0D semiconductor MXene quantum dots (MXene QDs). The QDs produced from MXenes showcase conductivity, hydrophilicity, and biocompatibility similar to that of MXenes along with distinctive optical and electrical properties. [18,19] They possess a lateral dimension of <10 nm, with abundant active sites and a greater surface-tovolume ratio compared to the parental MXene. These monodisperse nanocrystals exhibit semiconductor-like properties, size-dependent characteristics, and variable energy levels. [20] The edge defects and quantum confinement in the QDs account for their fluorescence emission. [21,22] The excellent light-harvesting properties also come advantageous for MXene QDs to be used in light-to-heat conversion applications. Ease of functionalization, high water dispersibility, good colloidal and photostability, as well as superior physicochemical and photoelectric activities contribute to promising applications of the MXene QDs in the fields of optics, photothermal conversion, photochemotherapy, fluorescence detection, and bioimaging. In 2017, the first prepared photoluminescent Ti 3 C 2 QDsThe progress of MXenes, a 2D layered structural material since its discovery in 2011 recently arouses a great deal of attention due to their plethora of applications in a diverse range of fields. Their excellent properties in terms of surface chemistry, optical activity, electrical conductivity, presence of abundant active catalytic sites, tunable band gap structure, ease of surface functionalization, and good biocompatibility make them an ideal candidate. The authors aim to guide the readers thr...

Ti3C2Tx MXene: A New Promising 2D Material for Optoelectronics

“…Changes in chemical and photophysical properties, such as increased surface area, quantum confinement, and edge effects, are also involved. So, the methods mentioned above are efficient for preparing MXene quantum dots by overcoming these challenges and further open a way for doping with different materials to enhance their properties. , …”

“…When comparing with layered Ti 3 C 2 T x MXene, Ti 3 C 2 T x QDs exhibit excellent optical properties attributed to quantum confinement effects. Also, Ti 3 C 2 T x QDs have a large specific surface area, tunable properties, and various hydrophilic functional groups . The Ti 3 C 2 MXene quantum dots (MQDs) were prepared by fluorine-free liquid exfoliation method, and they showed strong absorption in the NIR region with large extinction coefficients as high as 52.8 Lg –1 cm –1 .…”

Trends in Using Fluorescent MXene Quantum Dots for Selective Detection and Bioimaging Applications: A Review

“…It further indicates the emergence of MXene QDs in a multifarious application. Applications of MXene and MXene-based nanomaterial in biosensing, biomedicine, bioimaging, and several other fields have been published. ,− Sinha et al described the emergence of MXenes, their electronic properties, surface functionalization techniques, and their application in biosensing application . The authors explained the role of MXene in development of different biosensors including electrochemical, piezoresistive, and photoluminescent sensors.…”

“…The authors also highlighted the importance of different synthesis methods and characterization techniques in the synthesis of high-performance MXene QDs. Other studies also reported the diverse forms of application of MXene QDs in energy conversion and storage devices, biosensing, biomedical applications, and environmental pollutant sensing. , Studies also provided descriptions of the synthesis process and modification strategies.…”

The in situ decoration of Ti3C2 quantum dots on Cu nanowires for highly efficient electrocatalytic reduction of nitric oxide to ammonia

“…Recently, as a new type of two-dimensional layered material, Ti 3 C 2 MXene has been widely used as a catalyst or co-catalyst due to its large surface area, high surface activity, and unique electrical and electrochemical properties. [27][28][29][30][31] Tian et al 32 developed the efficient and highly selective 1T-MoS 2 @Ti 3 C 2 for electrocatalytic nitrogen fixation, showing a FE of 10.94% and NH 3 yield of 30.33 μg h −1 mg −1 . Liu et al 33 utilized Cu/Ti 3 C 2 as a catalyst with a FE of 7.31% and an NH 3 yield of 3.04 μmol h −1 cm −2 .…”