Near‐Infrared‐Emitting Nitrogen‐Doped Nanographenes

Abstract

The quantum‐size effect, which enables nanographenes to emit photoluminescence (PL) in the UV to visible region, has inspired intense research. However, the control of the PL properties of nanographenes through manipulation of their π‐system by post‐modifications is not well developed. By utilizing a ring‐closure reaction between an aromatic 1,2‐dicarboxylic acid and a 1,8‐naphthalenediamine derivative, which produces a perimidine framework, nitrogen‐doped nanographenes were realized. Two nanographenes produced by a one‐pot reaction of edge‐oxidized nanographene (GQD‐2) with 1,8‐naphthalenediamine derivatives (GQD‐1 a and GQD‐1 b) displayed an absorption band extending to >1000 nm; furthermore, the PL wavelength of GQD‐1 a was significantly red‐shifted into the near‐infrared (NIR) region in which it can be used for bioimaging. Time‐dependent DFT calculations of model nanographenes showed that the functional groups narrow the HOMO–LUMO gap, realizing the NIR‐emitting nanographenes.

Fluorescent Carbon‐ and Oxygen‐Doped Hexagonal Boron Nitride Powders as Printing Ink for Anticounterfeit Applications

“…Excitation in the range of 500–700 nm shows consistent NIR emission spectral shape (Figure S13, Supporting Information), which suggests that here excitation energy within the material “funnels” to these low energy states. This fits quite well with the previous suggestion of CQD formation within a BN matrix 31b,32…”

“…All BCNO samples show NIR emission resulting from such an excitation, with 650–850 °C treated samples emitting around 910 nm. This may be explained by different‐sized CQDs embedded in the BN lattice 31a,34. BCNO‐550‐1h shows a substantially redshifted emission by comparison (≈960 nm), which is also broader and more intense.…”

“…There is a clear blueshift of these absorption peaks, owing to reduced defects on the surface of the material with increasing temperature. The long absorption tails in the visible range indicates the presence of carbon cluster/carbon quantum dots (CQDs), and intra‐band impurity‐mediated transitions, which may be located at the surface, i.e., surface states . In addition to this, a further feature is found in the red/NIR (near‐infrared) portion of the spectrum, seen as a distinct peak for the BCNO‐850‐1h sample and as a shoulder for others.…”

Intrinsic Emission from Nanographenes

“…Nanographenes, also knowna sg raphene quantum dots, [1][2][3][4] have received considerable attention from researchers in many fields, owing to their uniqueo pticalp roperties, which arise from ab and gap that is caused by quantum confinement and edge effects. [5][6][7] The excellent properties of nanographenes, such as luminescence stabilitya nd low toxicity, make them promising candidatesf or ar ange of applications, [1][2][3][4] such as opticalm aterials, [8][9][10][11] polymers, [12] bioimaging, [13][14][15] and nanoscale optoelectronic devices. [10] Nanographenes can be produced by using various methods, such as organic synthesis [16][17][18][19][20][21] and bottom-up [22] and top-downm ethods.…”

A protocol for size separation of nanographenes

“…7 These features make them attractive research targets. Optical materials, 3,4,[8][9][10][11] polymers, 12 bioimaging, 5,13 photovoltaic devices, 14,15 electrocatalysts, 16 and nanomedicines 17 are examples of their applications.…”