Use Of Carbon Nanodots Research Articles

Novel Environmentally Friendly Nanomaterials for Drag Reduction of the Emulsified Acid System.

Matrix acidizing is a technique that is widely used in the petroleum industry to remove scales and create channels in the rock. Removal of scales and creation of channels (wormhole) enhance productivity. Conventional acidizing fluids, such as hydrochloric acid (HCl) for carbonate and a mixture of hydrofluoric acid (HF) and HCl acid, are used for the matrix acidizing process. However, these fluids have some drawbacks, including strong acid strength, corrosion at high temperatures, and quick reactions with scale and particles. Emulsified acid systems (EASs) are used to address these drawbacks. EASs can create deeper and narrower wormholes by reducing the reaction rate of the acid due to the external oil phase. However, EASs have a much higher viscosity compared to conventional acidizing fluids. The high viscosity of EASs leads to a high drag that restricts pumping rates and consumes energy. This study aims to utilize environmentally friendly and widely available nanomaterials as drag-reducing agents (DRAs) of the EAS. The nanomaterials used in this study are carbon nanodots (CNDs). CNDs have unique properties and are used in diverse applications in different industries. The size of these CNDs is usually smaller than 10 nm. CNDs are characterized by their biocompatibility and chemical stability. This study investigates the use of CNDs as DRAs for EAS. Several experiments have been conducted to investigate the CNDs as a DRA for the EAS. The developed EAS was initially tested for conductivity and drop-test analysis to ensure the formation of an inverted emulsion. Thereafter, the thermal stability for the range of temperatures and the rheological properties of the EAS were evaluated to meet the criteria of field operation. Then flow experiments with EASs were conducted before and after adding the CNDs to investigate the efficacy of drag reduction of EASs. The results revealed that CNDs can be used as viscosity reducers for the EAS, where adding the CNDs to the EAS reduces the viscosity at two different HCl concentrations (15 and 20%). It reduces the viscosity of the EAS in the presence of corrosion inhibitors as well as other additives to the EAS, showing its compatibility with the field formulation. The drag reduction was observed at the range of temperatures investigated in the study. The conductivity, stability, and rheology experiments for the sample taken after the flow experiment are consistent, ensuring CNDs work as a DRA. The developed EAS with CNDs is robust in terms of field mixing procedures and thermally stable. The CNDs can be used as a DRA with EAS, which will reduce drag in pipes, increasing pumping rates and saving energy.

Potential forensic applications of carbon nanodots

Nanotechnology is a flourishing branch of research due to the incredible properties nanomaterials exhibit over their massive counterparts. Carbon nanodots are the members of the carbon nanoparticle family with prominent properties like hydrophilicity, low toxicity, biocompatibility, increased stability and ease of functionalization. They are excellent replacement to metal based quantum dots which are highly toxic. Carbon nanodots are being used in the fields of medicine, environmental science, drug delivery and forensic science. Applications of carbon nanodots can be seen in bio imaging, bio sensing, cancer diagnosis and treatment, biological activities, solar cells and as photo catalysts. Forensic science is the science behind crime investigation and evidence analysis. Development of novel, rapid, on site testing materials for accurate, specific and sensitive detection of forensic evidences is required for delivery of justice to the victims of crime. Carbon nanodots have shown promising applications in the field of forensic science as well. Use of carbon nanodots as invisible ink for anti-counterfeiting application of currency and security documents and use of these nanomaterials in development of latent fingerprints are some forensic applications. Carbon nanodots based detection of food contaminants, heavy metal poisons, pesticides, illicit drugs and explosives are other forensic applications. Carbon nanodots are showing a future direction in development of on field testing kits for forensic evidences.

A promising approach to wound healing – in-vivo study of carbon nanodots infused PVA hydrogel with Kamias extract as antibacterial wound dressing

Introduction and aim. The use of carbon nanodots (C-nanodots) synthesized from Kamias leaves for developing antibacterial wound dressings has gained attention due to their potential in promoting wound healing and contraction. To extract Kamias leaves, synthesize C-nanodots through microwave-assisted pyrolysis, characterize the synthesized C-nanodots, and test the polyvinyl alcohol (PVA) hydrogel infused with C-nanodots for antibacterial activity and wound contraction in Sprague Dawley rats. Material and methods. Kamias leaves extract was used to synthesize C-nanodots with varying amounts of monoethanolamine. The C-nanodots were characterized using UV-Vis spectrophotometer, electron microscope, and the paper disk method. The PVA hydrogel infused with C-nanodots was tested for antibacterial activity and wound contraction in Sprague Dawley rats. Results. The synthesized C-nanodots exhibited antibacterial properties against Staphylococcus aureus and Subtilis bacillus, with a zone of inhibition ranging from 15 mm to 23.6 mm at different concentrations. The carbon nanodots-PVA hydrogel patch showed potential wound healing ability, with significant differences in wound contraction compared to the positive and negative controls. Conclusion. C-nanodots synthesized from Kamias extract have potential applications in antibacterial and wound healing fields. However, further studies are required to investigate the mechanism of action and potential side effects of using carbon nanodots in these applications.

Nitrogen-doped carbon nanodots deposited on titania nanoparticles: Unconventional near-infrared active photocatalysts for cancer therapy

Cancer represents a major public health issue and a primary cause of death for the mankind and the search for alternative cancer treatments that assist or alleviate the drawbacks of current cancer therapies remains imperative. Nanocatalytic medicine represents a new discipline that aims at exploiting the unique response of heterogeneous catalysts exposed to unconventional conditions such as those encountered in the tumor microenvironment (TME). Photo-triggered cancer therapies using light-activable catalytic materiales can stimulate and activate multiple biological processes and represent a very promising field of study. Herein, we evaluate the use of carbon nanodots with different composition (CNDs) retrieved by laser pyrolysis as potential near-infrared (NIR) photosensitizers able to activate P25 semiconductor nanostructured photocatalysts. We describe the enhanced photocatalytic response towards glucose conversion and reactive oxygen species (ROS) generation upon irradiation with NIR-LEDs when CNDs doped with heteroatoms were tested. The most active photocatalysts were evaluated in the presence of cancer cells and revealed a promising photodynamic effect under NIR irradiation. This work represents one of the scarce examples of a conventional inorganic photocatalyst containing TiO2 that is translated into a biomedical application with a successful outcome.

Surface vs. core N/S/Se-heteroatom doping of carbon nanodots produces divergent yet consistent optical responses to reactive oxygen species.

Carbon nanodots (CNDs) have attracted substantial scientific curiosity because of their intriguing stimuli-responsive optical properties. However, one obstacle to the more widespread use of CNDs as transducers for e.g., biodetection systems is incomplete knowledge regarding the underlying chemical changes responsible for this responsiveness, and how these chemical features can be engineered via the precursors chosen for CND synthesis. This study demonstrates that the precursor's functional groups play a key role in directing N/S/Se heteroatom dopants either towards the surface of the CNDs, towards the aromatic core, or towards small organic fluorophores in the core. Divergent optical properties, which were consistent amongst groups of CNDs prepared with similar precursors, were obtained including either a decrease or increase of fluorescence intensity in the presence of hydrogen peroxide. Moreover, CNDs were identified with orthogonal responsiveness to radical (hydroxyl radicals, ˙OH; down to 2.5 μM) vs. non-radical oxidants (H2O2; down to 50 μM), which suggests that control of the chemistry of CNDs via the choice of precursor could yield probes that are specific to certain sub-species of reactive oxygen species or entirely different molecules altogether, based on the way they chemically-modify the surface (respond faster) and core functional groups (respond slower) associated with chromophores/fluorophores of which the CNDs are composed.

A ratiometric electrochemiluminescent tetracycline assay based on the combined use of carbon nanodots, Ru(bpy)32+, and magnetic solid phase microextraction.

A method is described for combined magnetic solid phase microextraction and electrochemiluminescent (ECL) detection of the antibiotic tetracycline. A nanocomposite of type Fe3O4@SiO2@ZnO was used as the sorbent. Tetracycline has a strong affinity for Zn(II) ion and therefore is well extracted by this sorbent. The loaded sorbent can be magnetically removed. The extraction efficiency at a 1.0μM tetracycline concentration is around 88%. Detection is based on the use of carbon nanodots that were prepared form urea and ethylenediaminetetraacetic acid as raw materials. The electrochemical probe Ru(bpy)32+ was added to generate double ECL when scanning the potential between -3.5 and + 2V. The two ECL signals decreased with the increase of tetracycline concentration. Under optimized experimental conditions, the ratio of the two signals is linearly related to the logarithm of the tetracycline concentration in the range from 1.0nM to 0.1mM, with a 0.47nM detection limit. The method was successfully applied to the determination of tetracycline in spiked milk. It exhibited good sensitivity, selectivity and accuracy due to ratiometric read-out and prior preconcentration of analyte. Graphical abstract Tetracycline (TC) has a strong affinity for Zn(II) ion and is well extracted by the Fe3O4@SiO2@ZnO nanocomposite. Ru(bpy)32+ can generate double electrochemiluminescence signals based on the use of carbon nanodots (C-dots) as coreactant. The two signals decrease with the increase of tetracycline concentration. [Ru(bpy)32+]* stands for excited state Ru(bpy)22+.

Customizing the Electrochemical Properties of Carbon Nanodots by Using Quinones in Bottom‐Up Synthesis

AbstractWe show how the redox potentials of carbon nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during a microwave‐assisted synthesis. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad hoc applications, including photocatalysis.

Customizing the Electrochemical Properties of Carbon Nanodots by Using Quinones in Bottom-Up Synthesis.

We show how the redox potentials of carbon nanodots (CNDs) can be modulated by employing quinones as electroactive precursors during a microwave-assisted synthesis. We prepared and characterized a redox library of CNDs, demonstrating that this approach can promote the use of carbon nanodots for ad hoc applications, including photocatalysis.

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.

Using carbon nanodots as inexpensive and environmentally friendly sensitizers in mesoscopic solar cells.

We discuss the use of carbon nanodots (CNDs) as sensitizers in mesoscopic solar cells. The CNDs are synthesized using a one-step, bottom-up microwave approach with citric acid, urea, and formic acid as precursors in aqueous media. Their light-harvesting capabilities can be tuned by adjusting the synthetic parameters. Comprehensive spectroscopic and theoretical studies allow us to rationalize the nature of their absorption features. Promising power conversion efficiencies (η) of 0.24% can be achieved from these cheap and eco-friendly sensitizers by optimizing the solar-cell assembly process. Interestingly, we found that extending the light absorption towards longer wavelengths does not necessarily improve the performance of the solar cells, since the longer-wavelength absorption features hardly contribute to the cells' photo-action spectra, so that the overall power conversion efficiency is actually worse. The origin of the lower performance is corroborated in transient absorption spectroscopy and photovoltage decay measurements. Our work points, on one hand, to the limits of as-synthesized CNDs as photosensitizers and, on the other hand, to possible improvements.

Hydrothermal carbonization of carboxymethylcellulose: One-pot preparation of conductive carbon microspheres and water-soluble fluorescent carbon nanodots

Conductive carbon spheres (CSs) and water-soluble fluorescent carbon nano-dots (CNDs) were synthesized by the one-pot hydrothermal carbonization of carboxymethylcellulose (CMC) using urea as the nitrogen source. The CSs have diameters of 2–8μm and abundant nitrogen-containing functional groups. They contain N in two forms: (1) chemical N including amidogen and imido groups (NH2/NH), and (2) structural N including pyridine (N-6), pyrrolic/pyridone (N-5) and quaternary (N-Q) nitrogen. Activation at high temperature contributes to the formation of pyridine (N-6) and quaternary nitrogen (N-Q) with a graphite-like structure and higher stability. They are all conductive and CS0.2-900 was found to exhibit the highest electrical conductivity of 166S/m. CNDs are monodispersed spheres with an average diameter of 32nm and show abundant oxygen-containing groups on their surface. They have excitation- and emission-independent pH-sensitive properties. The use of CNDs as photosensitizer in a CNDs/TiO2 system for methylene blue and phenol degradation under visible light irradiation is attractive. The spectral response range of the system was thus expanded from UV region to include part of the visible light region.

Pentosan-derived water-soluble carbon nano dots with substantial fluorescence: Properties and application as a photosensitizer

Abstract The hydrothermal carbonization of monosaccharides and polysaccharides is widely used in the production of carbonaceous material with a desired structure. However, the liquid products are regarded as waste and discarded. Here, we report a facile approach for the synthesis of water-soluble carbon nano dots (CNDs) with substantial fluorescence from the liquid by-products of the hydrothermal carbonization of pentosan, thus the by-products of pulp refining. The synthesized CNDs are monodispersed spheres with abundant oxygen-containing groups and they have an average size of 30 nm. Quantum yield measurements revealed CNDs with substantial green photoluminescence (PL) without passivation. Additionally, excitation was independent, pH-sensitive and stable. The use of CNDs as a photosensitizer in the CNDs/TiO 2 system for methylene blue (MB) degradation under visible light irradiation is attractive. The spectral response range of the CNDs/TiO 2 system can be widened from the UV region to a part of the visible light region (400–550 nm).