Single Crystal, Luminescent Carbon Nitride Nanosheets Formed by Spontaneous Dissolution

Abstract

A primary method for the production of 2D nanosheets is liquid-phase delamination from their 3D layered bulk analogues. Most strategies currently achieve this objective by significant mechanical energy input or chemical modification but these processes are detrimental to the structure and properties of the resulting 2D nanomaterials. Bulk poly(triazine imide) (PTI)-based carbon nitrides are layered materials with a high degree of crystalline order. Here, we demonstrate that these semiconductors are spontaneously soluble in select polar aprotic solvents, that is, without any chemical or physical intervention. In contrast to more aggressive exfoliation strategies, this thermodynamically driven dissolution process perfectly maintains the crystallographic form of the starting material, yielding solutions of defect-free, hexagonal 2D nanosheets with a well-defined size distribution. This pristine nanosheet structure results in narrow, excitation-wavelength-independent photoluminescence emission spectra. Furthermore, by controlling the aggregation state of the nanosheets, we demonstrate that the emission wavelengths can be tuned from narrow UV to broad-band white. This has potential applicability to a range of optoelectronic devices.

Charged Carbon Nanomaterials: Redox Chemistries of Fullerenes, Carbon Nanotubes, and Graphenes

“…Intercalation of these compounds is well-established, including with group 1 metals; 463,464 however, exfoliation of gCN donorintercalation compounds has to-date relied on sonication in water, leading to severe damage and poor monolayer levels. Conversely, the smaller (sub-100 nm laterally), more crystalline PTI sheets are comparatively simple to process, spontaneously dissolving without charging as predominantly 8−9 layered species; 465 very recently, CCN chemistries have been shown to increase exfoliation to predominantly 2−3 layers at >30% yield, and allow functionalisation, under similar conditions to graphenides. 466 Lastly, although not yet demonstrated, there are new carbon allotropes that are expected to be susceptible to the same (electro)chemical methodologies as the other graphitic carbon nanomaterials.…”

Pharaoh's Serpents: New Insights into a Classic Carbon Nitride Material

“…[12,13] This interest in producing C 3 N 4 varieties was first stimulated by theoretical predictions that an sp 3 bonded framework structure might have "superhard" properties comparable to diamond, [14] but recent research has focused on graphitic layered structures based on sp 2 bonding. [13,[15][16][17] Interestingly, it has also been predicted that open framework varieties containing mixed sp 2 as well as sp 3 bonded units could exist. [18][19][20][21] Most carbon nitride materials under current investigation are produced by thermolytic condensation reactions of organic molecular precursors such as dicyandiamide (DCDA, C 2 N 4 H 4 ) and melamine [C 3 N 3 (NH 2 ) 3 ], giving rise to a range of polymeric C x N y H z compounds.…”

Fast Exfoliation and Functionalisation of Two‐Dimensional Crystalline Carbon Nitride by Framework Charging

“…Achieving an on-damaging preparation of 2D few-layered PTI (FL-PTI) in high yield is still in its infancy, although slow dissolution has recently been reported as av iable method. [8] Moreover,w hile covalent functionalisation is av ital tool in tailoring the properties of nanomaterials, [9] to date,there has been little direct covalent functionalisation of PTI.Herein, we describe the simple,o ne-pot exfoliation, dissolution, and optional functionalisation of FL-PTI by reduction. Av ariety of routes have been developed for reductive charging of 2D nanomaterials in solution, including the use of Birch reductions,m etal amalgam, and organic single electron charge transfer agents (CTAs).…”

“…[5] Unfortunately,many of these processes damage the structure,altering the properties of interest;t hey are also time-consuming,p rovide low yields and dilute suspensions,a nd rely mostly on disordered heptazine-based gCNs.P olytriazine imide (PTI) has been previously synthesized and characterized by an umber of bottom-up approaches. [8] Moreover,w hile covalent functionalisation is av ital tool in tailoring the properties of nanomaterials, [9] to date,there has been little direct covalent functionalisation of PTI. Achieving an on-damaging preparation of 2D few-layered PTI (FL-PTI) in high yield is still in its infancy, although slow dissolution has recently been reported as av iable method.…”

“…Achieving an on-damaging preparation of 2D few-layered PTI (FL-PTI) in high yield is still in its infancy, although slow dissolution has recently been reported as av iable method. [8] Moreover,w hile covalent functionalisation is av ital tool in tailoring the properties of nanomaterials, [9] to date,there has been little direct covalent functionalisation of PTI.…”