Energy shortage, environmental crisis, and developing customer demands have driven people to find facile, low-cost, environmentally friendly, and nontoxic routes to produce novel functional materials that can be commercialized in the near future. Amongst various techniques, the hydrothermal carbonization (HTC) process of biomass (either of isolated carbohydrates or crude plants) is a promising candidate for the synthesis of novel carbon-based materials with a wide variety of potential applications. In this Review, we will discuss various synthetic routes towards such novel carbon-based materials or composites via the HTC process of biomass. Furthermore, factors that influence the carbonization process will be analyzed and the special chemical/physical properties of the final products will be discussed. Despite the lack of a clear mechanism, these novel carbonaceous materials have already shown promising applications in many fields such as carbon fixation, water purification, fuel cell catalysis, energy storage, CO(2) sequestration, bioimaging, drug delivery, and gas sensors. Some of the most promising examples will also be discussed here, demonstrating that the HTC process can rationally design a rich family of carbonaceous and hybrid functional carbon materials with important applications in a sustainable fashion.

Engineering Carbon Materials from the Hydrothermal Carbonization Process of Biomass

Strongly green-photoluminescent graphene quantum dots for bioimaging applications

Fluorescent carbon nanoparticles (CNPs) 2−6 nm in size with a quantum yield of about ∼3% were synthesized via nitric acid oxidation of carbon soot, and this approach can be used for milligram-scale synthesis of these water-soluble particles. These CNPs are nanocrystalline with a predominantly graphitic structure and show green fluorescence under UV exposure. Nitric acid oxidation induces nitrogen and oxygen incorporation into soot particles, which afforded water solubility and a light-emitting property; the isolation of small particles from a mixture of different sized particles improved the fluorescence quantum yield. These CNPs show encouraging cell-imaging applications. They enter into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell imaging applications.

Fluorescent Carbon Nanoparticles: Synthesis, Characterization, and Bioimaging Application

One-step synthesis of amino-functionalized fluorescent carbon nanoparticles by hydrothermal carbonization of chitosan

Hydrothermal conversion of biomass waste to activated carbon with high porosity: a review.

In this report, we demonstrate glucose-derived carbon nanospheres(1) to be an emerging class of intracellular carriers. The surfaces of these spheres are highly functionalized and do not need any further modification. Besides, the intrinsic fluorescence property of carbon nanospheres helps in tracking their cellular localization without any additional fluorescent tags. The spheres are found to target the nucleus of the mammalian cells, causing no toxicity. Interestingly, the in vivo experiments show that these nanospheres have an important ability to cross the blood−brain barrier and localize in the brain besides getting localized in the liver and the spleen. There is also evidence to show that they are continuously being removed from these tissues over time. Furthermore, these nanospheres were used as a carrier for the membrane-impermeable molecule CTPB (N-(4-chloro-3-trifluoromethylphenyl)-2-ethoxybenzamide), the only known small-molecule activator of histone acetyltransferase (HAT) p300.(2) Biochemical...

Intrinsically Fluorescent Carbon Nanospheres as a Nuclear Targeting Vector: Delivery of Membrane-Impermeable Molecule to Modulate Gene Expression In Vivo

Shape-directed compartmentalized delivery of a nanoparticle-conjugated small-molecule activator of an epigenetic enzyme in the brain.

Background: Intrinsically fluorescent glucose derived carbon nanospheres (CSP) efficiently enter mammalian cells and also cross the blood brain barrier (BBB). However, the mechanistic details of CSP entry inside mammalian cells and its specificity are not known. Results: In this report, the biochemical and cellular mechanism of CSP entry into the living cell have been investigated. By employing confocal imaging we show that CSP entry into the mammalian cells is an ATPdependent clathrin mediated endocytosis process. Zeta potential studies suggest that it has a strong preference for cells which possess high levels of glucose transporters such as the glial cells, thereby enabling it to target individual organs/tissues such as the brain with increased specificity. Conclusion: The endocytosis of Glucose derived CSP into mammalian cells is an ATP dependent process mediated by clathrin coated pits. CSPs utilize the surface functional groups to target cells containing glucose transporters on its membrane thereby implicating a potential application for specific targeting of the brain or cancer cells.

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ATP driven clathrin dependent entry of carbon nanospheres prefer cells with glucose receptors

Purpose: To determine the impact of hypothermia on the barrier function of donor corneal endothelium, thereby enhancing the success of corneal transplantation. Methods: Primary cultures of porcine ...

B. S. Suma

Papers

Intrinsically Fluorescent Carbon Nanospheres as a Nuclear Targeting Vector: Delivery of Membrane-Impermeable Molecule to Modulate Gene Expression In Vivo

Shape-directed compartmentalized delivery of a nanoparticle-conjugated small-molecule activator of an epigenetic enzyme in the brain.

ATP driven clathrin dependent entry of carbon nanospheres prefer cells with glucose receptors

Microtubule Stabilization Protects Hypothermia-Induced Damage to the Cytoskeleton and Barrier Integrity of the Corneal Endothelial Cells