Preparation Of Carbon Nanodots Research Articles

Preparation of Carbon Nanodots with Ultraviolet Emission by Pulsed Laser Ablation

To date, it is still a challenge to acquire carbon nanomaterials with ultraviolet (UV) emission due to the trapping of excited carriers by defect states and surface groups. Herein, a pulsed laser ablation (PLA) method without any post‐treatments is developed to prepare carbon nanodots (CNDs). The cores of the resulting CNDs are graphitic carbon with negligible defects, whereas the surfaces are passivated by simple oxygen‐related groups, which is demonstrated by high‐resolution transmission electron microscope (HRTEM) image, X‐ray diffraction (XRD) pattern, and Raman spectra. Thus, the trapping of excited carriers by defect states and surface groups is substantially suppressed. As a consequence, the CNDs exhibit inherent UV emission of carbon nanostructures. The excitation‐independent UV emission peak contains three sub‐bands at 305, 325, and 335 nm. This work develops an approach for the preparation of UV‐emissive CNDs, which expands the applications of CNDs to UV‐related areas.

Facile Preparation of Phthalocyanine-Based Nanodots for Photoacoustic Imaging and Photothermal Cancer Therapy In Vivo

The development of near-infrared (NIR)-absorbing nanoagents for personalized multifunctional phototheranostics has attracted considerable attention in the past decade. Recently, the organic nanomaterials with good biosafety are considered as promising phototheranostic agents, while their facile synthesis remains challenging. Inspired by the preparation of carbon nanodots, we fabricate the NIR-absorbing phthalocyanine-based nanodots (ZnPc-NDs) using a facile method for multifunctional phototheranostics. The significant aggregation of phthalocyanines in nanodots induces a complete fluorescence quenching, which affords a high photothermal conversion efficiency (η = 45.7%). The ZnPc-NDs disperse very well in water media with an average diameter around 80 nm. Further conjugation of biotin on the surface of ZnPc-NDs affords tumor-targeting phthalocyanine nanodots (ZnPc-BT). The ZnPc-BT are demonstrated with favorable biocompatibility, intense photoacoustic signals, high tumor accumulation, and effective tumor suppression in vivo. This Article provides a new insight for further developing nanomedicines with imaging and therapeutic functions to treat cancers precisely and effectively.

Uniform luminescent carbon nanodots prepared by rapid pyrolysis of organic precursors confined within nanoporous templating structures

Although several methods on the preparation of carbon nanodots (CNDs) emitting throughout the visible have been recently reported, in most of the processes the product suffers from inhomogeneity in size and shape limiting their impact. Here, we report the synthesis of undoped and nitrogen-doped luminescent carbon nanodots by rapid pyrolysis using ordered mesoporous silica nanorods as confining templates. A rapid thermal decomposition (pyrolysis) within the confined dimensions of their pores leads to a highly uniform size distribution of CNDs with average sizes below 4 nm. These CNDs are synthesized in an extremely short time period (5 min of reaction) by immersion in a fluidized-bed reactor that provides heating homogeneity and ensures fast heat transfer. In addition, a rapid release of the homogeneous CNDs can be easily achieved by a simple ultrasonication-filtration step that prevents further chemical action on the mesoporous templates. The emission of both undoped and N-doped CNDs in colloidal and solid state (with an efficiency of 1–5%) originates from a combination of quantum confinement effects and the presence of oxidized surface states; N-doping introduces resonant absorption states which participate in emission. Furthermore, we present a simple model to describe the excitation-dependent/-independent mechanism of carbon nanodots.

Light‐Active Carbon Nanodots from Autoclaved Bioresources

AbstractThe preparation of carbon nanodots (CNDs) from living organisms can be expected to incur lower energy costs than existing CND synthesis methods. Here, water‐soluble and well‐dispersed fluorescent CNDs with high biocompatibility were synthesized from a variety of biological resources, i. e., arthropods and biomolecules, via a simple single‐step hydrothermal treatment. The as‐prepared CNDs exhibited a blue fluorescence, with a quantum yield of up to 1.5 %. Additionally, we discovered that synthesized CNDs can be transformed into carbon‐nanosheet structures through exposure to low‐intensity laser irradiation. High thermal energy is also generated. We further explored the use of CNDs with this powerful photothermal property as novel exothermic nanomaterials for the elimination of cancer cells. This new type of light‐active CND has considerable promise as regards the development of a variety of biological applications.

Large‐Scale Green Synthesis of Fluorescent Carbon Nanodots and Their Use in Optics Applications

An easy and green synthetic strategy for the one‐pot large‐scale preparation of carbon nanodots (C‐dots) is demonstrated. The C‐dots have a series of excellent optical features such as strong fluorescence and excitation‐wavelength‐dependent photoluminescence properties. Notably, C‐dots can be rapidly and facilely achieved on a large scale (e.g., 0.3 g C‐dots/25 min) by using cheap, accessible, and natural materials (e.g., milk, honey, silk, hair, lemon, and magnolia) as the green carbonaceous precursor. The as‐prepared C‐dots, which are shown to serve as high‐performance fluorescent stains, are superbly suitable for a variety of optics‐related applications, including in vitro and in vivo bioimaging, printing inks, and sensors. Eventually, this kind of microwave‐assisted strategy could serve as a powerful tool for synthesizing large‐scale C‐dots with strong fluorescence, holding great promise for myriad optics‐related applications.

Preparation of carbon nanodots from single chain polymeric nanoparticles and theoretical investigation of the photoluminescence mechanism

Even after several years of research, controlled synthesis of photoluminescent carbon nanodots (C-dots) still constitutes a major challenge, and investigation of their photoluminescence (PL) mechanism remains elusive. Various top-down and bottom-up approaches have been reported lately. However, these methods usually suffer from limited control over the major factors that dictate the PL behaviour of these fascinating carbon materials. To this end, we discover a new approach to prepare C-dots from size-tunable single chain polymeric nanoparticles. Taking advantage of the state of the art living radical polymerization technique and unique features of Bergman cyclization, narrowly dispersed C-dots are prepared in a straightforward manner. PL study shows that the optimal emission wavelength of C-dots red-shifts when the size of C-dots decreases, which is different from the trends typically found in semiconductor quantum dots and C-dots prepared from graphitized materials. To clarify the PL mechanism of C-dots prepared from different sources, a theoretical study based on density functional theory is performed. Two series of model compounds, fused aromatic rings and cyclo-1,4-naphthylenes, are chosen for C-dots with different microstructures. The calculation data indicate that PL energy of C-dots is dictated by the size and microstructure of the sp2 carbon core. For a C-dot with a graphitized core, the smaller the size of the core, the higher the PL energy, while for a C-dot with an amorphous core, an inverse trend is revealed. Surface reduction experiments further show that the quantum yield of C-dots is controlled by the surface chemistry.