Functional COOH Research Articles

Interfacial Electron Beam Lithography Converts an Insulating Organic Monolayer to a Patterned Single-Layer Conductor with Puzzling Charge Transport Performance.

The direct generation of conducting paths within an insulating surface represents a conceptually unexplored approach to single-layer electrical conduction that opens vistas for exciting research and applications fundamentally different from those based on specific layered materials. Herein we report surface channels with single-layer -COOH functionality patterned on insulating n-octadecyltrichlorosilane monolayers on silicon that exhibit unusual ionic-electronic conduction when equipped with ion-releasing silver electrodes. The strong dependence of charge transport in such channels on their lateral dimensions (nanosize, macro-size), the type (p, n) and resistivity (doping level) of the underlying silicon substrate, the nature of the insulating spacer layer between the conducting channel and the silicon surface, and the postpatterning chemical manipulation of channel's -COOH functionality allows designing channels with variable resistivities, ranging from that of a practical insulator to some unexpectedly low values. The unusually low resistivities displayed by channels with nanometric widths and micrometer-millimeter lengths are attributed primarily to enhanced electronic transport within ultrathin nanowire-like silver metal films formed along their conductive paths. Function-structure correlations derived from a comprehensive analysis of electrical, atomic force microscopy, and Fourier transform infrared spectral data suggest an unconventional mode of conduction in these channels, which has yet to be elucidated, apparently involving coupled ionic-electronic transport mediated and enhanced by interfacial electrical interactions with charge carriers located outside the conducting channel and separated from those carrying the measured current. These intriguing findings hint at effects akin to Coulomb pairing in the proposed mechanisms of excitonic superconductivity in interfacial nanosystems structurally related to the present metalized surface channels.

Thiolated Cyanines Appended to Partially Pegylated Gold Nanoparticles for Fluorescence Quenching of Two-Channel Photothermal Inks.

Following a new approach, we prepared a nanoink with two separate photothermally responsive absorption bands. One is the localized surface plasmon resonance (LSPR) absorption of gold nanoparticles (AuNP, d=17 nm), the second is the absorption band of two cyanine (Cy) dyes, Cy7-C6 or Cy7-C11, grafted to the AuNP surface through thiolated bridges of different lengths: the close proximity to the Au surface induces full quenching of the Cy fluorescence, resulting in thermal relaxation on irradiation. Attempts to full coat AuNP with the lipophilic Cy7-C6 and Cy7-C11 lead to precipitation from aqueous solutions. We thus prepared AuNP with partial pegylation (30, 50, or 70 %), using a long chain thiol-terminated PEG bearing a -COOH function. Addition until saturation of either Cy7-C6 or Cy7-C11 to the partially pegylated AuNP gave the AuNP@Cy/PEGX% hybrids (X=30, 50, 70) that are stable in water and in the water/alcohol mixtures used to prepare the nanoinks. Further overcoating of AuNP@Cy7-C6/PEG50 % with PAH (polyallylamine hydrochloride) avoids LSPR hybridization in the dry nanoink printouts, that present two separate bands. When irradiated with laser sources near their absorption maxima, the printouts of the AuNP@Cy7-C6/PEG50 %@PAH nanoink respond on two channels, giving different temperature increases depending on the irradiation wavelengths. This enhances the potentiality of use of these nanoinks for photothermal anticounterfait printouts, making more difficult to reproduce the correct ΔT vs λirradiation output.

Broken crystal symmetry of MWCNTs as the key factor in improvement of carboxyl functionalization

Carbon nanotubes functionalized with carboxyl groups (COOH-CNTs) find their application in energy storage, sensing, improving mechanical stability and biomedicine. So a facilitation of COOH-groups bonding to CNTs is one the modern scientific challenges. In this study untreated multi-walled CNT (MWCNTs), nitrogen-doped MWCNT (N-MWCNTs) and ion-beam irradiated N-MWCNTs (irr-N-MWCNTs) were synthesized using the CVD method. Characterizations were performed via HRTEM, Raman, XPS, and NEXAFS spectroscopy. Irr-N-MWCNTs demonstrated the largest amount of carbon crystallites, the presence of Stone-Wales defects as well as the regions of tensile-compressive, shear and torsional deformation. All these factors contributed to increase of carboxyl functionalization at the tube’s surface. On the base of experimental data, the atomic supercells of N-MWCNTs and irr-N-MWCNTs were built by the self-consistent-charge density-functional tight-binding method (SCC DFTB). Through SCC DFTB, we quantified atomic rearrangements, electronic structures, charge transfers, total energies, and the forces and energy barriers relevant to COOH bonding. The twisting of irr-N-MWCNTs supercells by 45 degrees decreased the barrier to the carboxyl formation in 2.5 times in comparison to undeformed nanotubes. Our findings reveal that nitrogen addition, ion-beam irradiation, and induced deformations create the necessary conditions for COOH functionalization by altering the physicochemical surface properties of MWCNTs.

Investigation into the role of carboxylic acid and phenolic hydroxyl groups in the plant biostimulant activity of a humic acid purified from an oxidized sub-bituminous coal.

Humic substances (HS) are increasingly being applied as crop plant biostimulants because they have been shown to increase plant productivity, especially under environmentally stressful conditions. There has been intense interest in elucidating the HS molecular structures responsible for eliciting the plant biostimulant response (PBR). The polar and weakly acidic carboxylic (COOH) and phenolic hydroxyl (ArOH) functional groups play major roles in the acid nature, pH dependent solubilities, conformation, and metal- and salt-binding capabilities of HS. Reports on the role played by these groups in the PBR of HS found growth parameters being both positively and negatively correlated with COOH and ArOH functionalities. To investigate the role of COOH and ArOH in HS biostimulant activity we used a humic acid (HA), purified from an oxidized sub bituminous coal to prepare HAs with COOH groups methylated (AHA), ArOH groups acetylated (OHA), and with both COOH and ArOH groups methylated (FHA). The original HA was designated (NHA). The four HAs were subjected to elemental, 13C-NMR, FTIR, and EPR analyses and their antioxidant properties were assessed using the trolox equivalents antioxidant capacity assay (TEAC). 13C-NMR and FTIR analysis revealed significant alkylation/acetylation. To determine the effects of alkylating/acetylating these functional groups on the HA elicited PBR, the HAs were evaluated in a plant bioassay on corn (Zea mays L.) seedling under nutrient and non-nutrient stressed conditions. Treatments consisted of the four HAs applied to the soil surface at a concentration of 80 mg C L-1, in 50 ml DI H2O with the control plants receiving 50ml DI H2O. The HA-treated plants, at both fertilization rates, were almost always significantly larger than their respective control plants. However, the differences produced under nutrient stress were always much greater than those produced under nutrient sufficiency, supporting previous reports that HA can reduce the effects of stress on plant growth. In addition, for the most part, the HAs with the alkylated/acetylated groups produced plants equal to or larger than plants treated with NHA. These results suggests that COOH and ArOH groups play a limited or no role in the HA elicited PBR. Alternatively, the HA pro-oxidant to antioxidant ratio may play a role in the magnitude of the biostimulant response.

Hafnium coordination vitrimer based on carboxylate exchange: synthesis, properties, and mechanistic investigations on the [Hf6O4(OH)4(O2CMe)12]2 model compound

AbstractA hafnium‐based coordination vitrimer (Hf−CooAN‐10) has been prepared by carboxylate ligand exchange from [Hf6O4(OH)4(O2CMe)12]2 and poly‐((ethylhexyl methacylate)‐co‐(carboxyethyl acrylate)) (Mn = 14.4 kg mol−1, Đ = 2.2, 90 : 10 comonomer molar ratio), using a 10 % molar Hf loading with respect to the polymer maximum crosslinking capacity. The material shows high insoluble fraction and expected properties for a 3D network and has been reshaped three times at 50 °C under a 3‐ton pressure without significant property alteration. The Hf−CooAN‐10 thermomechanical and rheological properties are very similar to those previously reported for the analogous Zr−CooAN‐10. The associative nature of carboxylate exchange between the [Hf6O4(OH)4(O2CR)12] crosslinks and the polymer matrix free −COOH functions is suggested by parallel 1H NMR line‐broadening kinetic investigations of acetate exchange in the [Hf6O4(OH)4(O2CMe)12]2 precursor with free MeCOOH, the rate of which has a zero‐order dependence on [MeCOOH], and by DFT calculations on a [Hf(μ‐O2CMe)(O2CMe)2(OH)(H2O)]2 model. The results of these investigations, including the activation parameters for the exchange of both chelating and bridging ligands, are very similar to those of the previously investigated zirconium system and suggest partial acetate dissociation assisted by H‐bond formation with a (μ3‐OH) ligand as the rate‐determining step, followed by acid coordination and intramolecular proton transfer.

Gadolinium-Doped Carbon Nanodots as Potential Anticancer Tools for Multimodal Image-Guided Photothermal Therapy and Tumor Monitoring.

This study focuses on the synthesis and characterization of gadolinium-doped carbon nanodots (CDs-Gd) and their potential applications in multimodal imaging and precision cancer therapy. CDs-Gd were synthesized through a solvothermal decomposition method combining citric acid, GdCl3, and urea. The incorporation of Gd3+ ions within the carbonaceous structure resulted in stable CDs-Gd with a peculiar architecture that retained optical and paramagnetic properties. Combined characterization techniques confirmed the presence of pH-sensitive COOH functions on the CDs-Gd surface along with the unique lattice structure induced by Gd3+ doping. The optical properties of CDs-Gd exhibited a tunable emission spectrum displaying blue-green emission with pH-dependent behavior. Additionally, CDs-Gd exhibited contrast-enhancing properties in T1-weighted magnetic resonance imaging (MRI) experiments. MRI acquisitions at different Gd3+ concentrations and pH values demonstrated the potential of CDs-Gd as contrast agents for monitoring pH changes in an aqueous environment. We found that the relaxivity of CDs-Gd at pH 5.5 (tumor, 11.3 mM-1 s-1) is roughly 3-fold higher than that observed at pH 7.4 (physiological, 5.0 mM-1 s-1) and outperformed clinical standards such as γ-butyrol (3.3 mM-1 s-1). Monitoring pH changes in tumor microenvironment (TME) is crucial for evaluating the effectiveness of anticancer treatments and understanding tumor progression. Furthermore, CDs-Gd demonstrated concentration-dependent photothermal conversion ability in the near-infrared (NIR) region, allowing for efficient heat generation under laser irradiation. This indicates the potential application of CDs-Gd in image-guided photothermal therapy (IG-PTT) for cancer treatment. The in vitro studies on MCF-7 (breast cancer) and 16-HBE (healthy bronchial epithelium) cell lines demonstrated that CDs-Gd exhibited high biocompatibility (cell viability >80%). However, upon NIR activation, they showed potent anticancer effects by inhibiting tumor cell proliferation and inducing apoptosis selectively in cancer cells. In conclusion, the synthesized CDs-Gd nanoparticles possess unique optical, photothermal, and MRI contrast properties, making them promising candidates for multimodal imaging-guided precision cancer therapy applications.

Statistically optimised sequestration of mefenamic acid from polluted water by acacia gum phthalate/pectin hydrogel: A novel multifunctional adsorbent material synthesised via microwave-assisted process

Pharmaceuticals and personal care products (PPCPs) are an emerging class of perilous pollutants due to their potential inimicalimpacts on ecosystems necessitating their abatement.Herein, an environmentally-affable and multifunctional acacia gum phthalate/ pectin hydrogel (AGP/PEC) was innovatively synthesised by microwave-assisted free-radical polymerisation for subsequent mefenamic acid (MFA) decontamination from synthetic wastewater. The physicochemical characteristics of AGP/PEC was studied through FTIR, XRD, BET, TEM, SEM-EDX and XPS characterisation techniques showing the existence of –OH and –COOH functionalities, rough surface with good surface area (18.95 m2/g) and porosity that contributed to high MFA uptake (93.45%) via hydrogen-bonding, electrostatic, pore-filling, π−π, and n−π interactions. The independent and interactive influences of operative variables on the adsorption capacity of AGP/PEC was statistically evaluated via central composite design of response surface methodology. The most-effective MFA uptake was attained at optimal operating conditions: initial solution pH (5.9), dosage (0.4 g/L), and time (28.5 min). Langmuir isotherm with Qm = 103.43 mg MFA/g and pseudo-second order kinetic models best-correlated the corresponding data. The Qm increased with temperature specifying an endothermic process, which was authenticated by positive ΔH⁰ (= 7.75 kJ/mol). The parameter, bT = 0.16 kJ/mol and ED = 2.12 kJ/mol, calculated from Temkin and Dubinin−Radushkevich isotherm models, respectively specified physisorption. The better adsorptive competence in real water along with an excellent reusable potential (87.1%) up to fifth cycle designated AGP/PEC as a potent adsorbent for practical purposes. These findings accentuated that AGP/PEC could be gainfully implemented as green and advanced multifunctional adsorbent material for removing residual MFA from wastewater.

Supersensitive metal free in-situ synthesized graphene oxide@cellulose nanocrystals acetone sensitive bioderived sensors

A series of graphene oxide@cellulose nanocrystal (GO@CNC) nanoparticles (NPs) were synthesized in this study using a room temperature-based simple modified hummers process. The morphological structures, as well as chemical characteristics of these materials, were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and other techniques. The results show that the as-prepared nanoparticles are made up of crystallite grains with an average size of around 7.82, 14.69, 10.77, 7.82, and 12.51 nm for GO, CNC, GO1@CNC1, GO2@CNC3, and GO3@CNC3 respectively, and OH &COOH functionalities on the NPs' surfaces. GO@CNC NPs exhibit significantly better sensing characteristics towards acetone when compared to virgin GO nanoplatelets; specifically, the optimal sensor based on GO3@CNC3 NPs showed the highest response (60.88 at 5 ppm), which was higher than that of the virgin GO sensor at 200 °C operating temperature and including those reported. Furthermore, the sensors have a high sensitivity towards acetone in sub-ppm concentrations as well as a detection limit of 5 ppm, making it a viable candidate for diabetes breath testing.

PIB-based block copolymer with a segment having alternating sequence of leucine and alanine side-chain pendants

A family of block copolymers with a hydrophobic polyisobutylene segment and another segment with an alternating sequence of tert-butoxy carbonyl (Boc)-leucine containing maleimide unit and Boc-alanine containing styrene unit was synthesized using a combination of living cationic and reversible addition-fragmentation chain transfer polymerizations. After successful deprotection of the Boc-groups from the pendant amino acids, the block copolymers become amphiphilic with free –NH3 + and –COOH functionalities in an alternating fashion in the poly(maleimide-alt-styrene) segment. The alternating sequence of leucine and alanine pendants throughout the second segment of the block copolymer chain was investigated systematically using NMR spectroscopy. In the pH range of 2–9, the deprotected copolymers showed pH-induced transformation of polymeric self-assemblies with critical aggregation concentrations ∼28 and ∼30 mg/L at pH 2 and pH 9, respectively. The pH-induced morphological transformation was well evidenced by 1H NMR spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy analysis. Additionally, these block copolymeric self-assemblies were studied for delivery applications at different pH, using Nile red as a model hydrophobic dye molecule.

Colorimetric detection of silver ions in different pH conditions using Pongamia pinnata leaf extract derived carbon dots

In this study, carbon dots (PPCDs) with OH and COOH functional groups were synthesized using Pongamia pinnata leaf extract as a carbon source by oxidation and a hydrothermal process. The colorimetric sensing results reveal the intensity of PPCDs enhancement upon the addition of the different concentrations of the silver ions, with LODs of 7.8, 0.758, and 0.340 μM in 5.1, 7.2, and 10 pH conditions, respectively. On the other hand, point-of-care kit (POC) data exhibits an intensive band that appeared after the addition of the silver ions at three pH conditions. The formation of the OH and COOH functionalities on the surface of the PPCDs might be responsible for the highly selective and sensitive detection of the Ag+ ions through metal–ligand charge transfer complex formation.

Release of Bioactive Molecules from Graphene Oxide-Alginate Hybrid Hydrogels: Effect of Crosslinking Method

To investigate the influence of crosslinking methods on the releasing performance of hybrid hydrogels, we synthesized two systems consisting of Graphene oxide (GO) as a functional element and alginate as polymer counterpart by means of ionic gelation (physical method, HA−GOP) and radical polymerization (chemical method, HA−GOC). Formulations were optimized to maximize the GO content (2.0 and 1.15% for HA−GOP and HA−GOC, respectively) and Curcumin (CUR) was loaded as a model drug at 2.5, 5.0, and 7.5% (by weight). The physico-chemical characterization confirmed the homogeneous incorporation of GO within the polymer network and the enhanced thermal stability of hybrid vs. blank hydrogels. The determination of swelling profiles showed a higher swelling degree for HA−GOC and a marked pH responsivity due to the COOH functionalities. Moreover, the application of external voltages modified the water affinity of HA−GOC, while they accelerated the degradation of HA−GOP due to the disruption of the crosslinking points and the partial dissolution of alginate. The evaluation of release profiles, extensively analysed by the application of semi-empirical mathematical models, showed a sustained release from hybrid hydrogels, and the possibility to modulate the releasing amount and rate by electro-stimulation of HA−GOC.

BODIPY Immobilized MCM‐41 Based Multianalyte Sensor: Application in Detection and Removal of Trivalent (Al3+, Cr3+) and Divalent (Cu2+, Hg2+) Metal Ions in Aqueous Media

AbstractIn the present study, a novel p‐phenylcarboxylic acid BODIPY (L) immobilized MCM‐41 based solid chemosensor material L‐propylsilyl@MCM‐41 (MS4) was developed to detect multiple metal ions in a pure aqueous medium. The synthesized solid chemosensor material MS4 shows high sensitivity and removal ability towards trivalent (Al3+, Cr3+) and divalent (Cu2+, Hg2+) metal ions. The emission intensity of MS4 enhanced multifold selectively in the presence of trivalent (Al3+, Cr3+) metal ions and shows quenching in the presence of divalent (Cu2+, Hg2+) metal ions. The limit of detection was calculated to be in the nanomolar range with Al3+, Cr3+, Cu2+, and Hg2+ metal ions in the aqueous medium. The spectroscopic and analytical results suggest that MS4 selectively binds with Al3+ and Cr3+ through −NH functionality and with Hg2+ and Cu2+ through −COOH functionality of p‐phenylcarboxylic acid BODIPY (L). Further, MS4 selectively removes Al3+, Cr3+, Cu2+, and Hg2+ metal ions from the aqueous media with removal efficiency of 97.28 %, 96.34 %, 87.19 %, and 95.63 %, respectively. No noticeable change in the concentration was observed for other metal ions. The recycling potential of MS4 was evaluated using EDTA for up to seven cycles with no significant reduction in sensing capability.

Chitosan-Based Ciprofloxacin Extended Release Systems: Combined Synthetic and Pharmacological (In Vitro and In Vivo) Studies.

Ciprofloxacin is one of the most effective antibiotics, but it is characterized by a range of side effects. Elaboration of drug-releasing systems which allow to diminish toxicity of ciprofloxacin is a challenging task in medicinal chemistry. The current study is focused on development of new ciprofloxacin releasing systems (CRS). We found that ultrasound efficiently promotes N,N'-dicyclohexyl carbodiimide-mediated coupling between COOH and NH2 functionalities in water. This was used for conjugation of ciprofloxacin to chitosan. The obtained ciprofloxacin/chitosan conjugates are capable of forming their self-assembled nanoparticles (SANPs) in aqueous medium. The SANPs can be additionally loaded by ciprofloxacin to form new CRS. The CRS demonstrated high loading and encapsulation efficiency and they are characterized by extended release profile (20 h). The elaborated CRS were tested in vivo in rats. The in vivo antibacterial effect of the CRS exceeded that of the starting ciprofloxacin. Moreover, the in vivo acute and subacute toxicity of the nanoparticles was almost identical to that of the chitosan, which is considered as the non-toxic biopolymer.

Effects of Carboxyl Functionalized CNT on Electrochemical Behaviour of Polyluminol-CNT Composites

The effect of carboxyl groups on the redox activity of polyluminol-carbon nanotube composites was studied. Carboxyl groups were selected due to their known contributions toward surface wettability and pseudocapacitance while often present on naturally derived low-cost porous carbons. Density functional theory (DFT) predicted energetically favoured bonding and a significantly reduced band gap between the luminol and carboxylated graphene relative to that of bare graphene, suggesting improved charge storage for carboxylated carbon substrates. The prediction was validated using bare carbon nanotubes (CNTs) and carboxylated CNTs (COOH-CNTs) as the substrates for in situ chemical polymerized luminol (CpLum). Surface morphological studies showed a ca. 1.1 nm thick coating of CpLum on CNT (CpLum/CNT) and a ca. 1.3 nm on COOH-CNT (CpLum/COOH-CNT), while surface chemical analysis revealed ca. 10% nitrogen from CpLum on both CpLum/CNT and CpLum/COOH-CNT. However, with merely 4.4% of COOH functionalization, CpLum/COOH-CNT was able to store more charge (137.1 ± 17.1 C cm−3) relative to CpLum/CNT (86.1 ± 14.1 C cm−3) and had increased charge retention over 5000 cycles. The insights from these studies can be used to engineer the surface of carbons such as CNTs and ACs to improve the interfacial properties for redox active materials and composites.

Facile synthesis and study of functional porous organic polyaminals with ultrahigh adsorption capacities and fast removal rate for rhodamine B dye

In this work, a series of low-cost novel porous organic polyaminals (POAs) were constructed through a one-pot catalyst-free Schiff-base condensation reaction with simple triazine-based multiamines and commercial aromatic aldehydes. These resulting porous polymer materials exhibited BET surface areas of 470–814 m2 g−1 and hierarchical pore distributions in the range of 0.58–1.63 nm. Owing to their high surface areas, hierarchical pore distributions, nitrogen-rich skeletons, and favorable water dispersibility accompanied by functional COOH and OH groups, POAs displayed high adsorption capacities and fast adsorption process of rhodamine B (RhB) for 1851, 1810, and 2161 mg g−1 of POA-Ph, POA-OH, and POA-COOH. These RhB adsorption capacities exceeded those of most of the reported POP materials. The theory simulation was introduced to comprehend the host-guest interaction adjustment between POAs and RhB molecules. Meanwhile, the perfect dynamic column adsorption modeling experiments revealed the high-efficiency adsorption separation abilities of POAs approaching actual application situations. These excellent adsorption properties made POAs good candidates for potential applications in water treatment. This study provides useful guidance for the design and preparation of low-cost and highly efficient POP dye adsorption materials.

Synergistic effect of –COOH and Zr(IV) with a short distance in Zr-MOFs for promoting utilization of H2O2 in oxidative desulfurization

The effectiveness of the catalytic oxidative desulfurization (CODS) process crucially depends on the catalytic activity of the catalyst and the utilization of oxidizing agent. Catalyst with multiple active sites is an effective method to improve the CODS effectiveness. The Zr(IV) and –COOH-containing metal–organic framework, UiO-66-(COOH)2, was synthesized and used as an active and recyclable catalyst for CODS. The UiO-66-(COOH)2 shows higher catalytic activity and H2O2 utilization in the CODS process than UiO-66/–COOH, UiO-66, and H2BDC. And the high catalytic performance is derived from the synergistic effect between the Zr(IV) open site and free –COOH functionality within the framework. Experimental analysis and DFT calculations results indicate that the synergistic effect, which changes the reaction path and protects the *O2– radical, is a very effective strategy to promote desulfurization efficiency and the utilization efficiency of H2O2. In addition, it is essential to highlight that the active-site distance also has a significant influence on the effectiveness of CODS. This research may provide a new avenue for improving the CODS performance.

Probing the Interaction of Heavy and Transition Metal Ions with Silver Nanoparticles Decorated on Graphene Quantum Dots by Spectroscopic and Microscopic Methods.

We report a comprehensive study of the interaction of transition and heavy metal ions with graphene quantum dots-capped silver nanoparticles (AgGQDs) using different spectroscopic and microscopic techniques. High-resolution transmission electron microscopy studies show that the interaction of metal ions with AgGQDs leads to the formation of metal oxides, the formation of zerovalent metals, and the aggregation of Ag nanoparticles (AgNPs). The metal ions may interact with AgGQDs through selective coordination with -OH and -COOH functionalities, adsorption on the graphene moiety, and directly to AgNPs. For instance, the interaction of Cd2+ with AgGQDs altered the spherical shape of AgNPs into a chain-like structure. On the contrary, the formation of PbO is observed after the addition of Pb2+ to AgGQDs. Interestingly, the interaction of AgGQDs with Hg2+ results in the complete dissolution of Ag0 from the surface of GQDs and subsequent deposition of Hg0 on the graphene moiety of GQDs. Unlike transition metal ions, Cd2+, Pb2+, and Hg2+ can adsorb strongly on the graphene surface at the bridge, hollow, and top sites, respectively. This special interaction of heavy metal ions with the graphene surface would decide the mechanistic pathway in which the reaction proceeds. The transition metal ions Cu2+, Zn2+, Co3+, Mn2+, Ni2+, and Fe3+ induced the aggregation of AgNPs.

Diminished Fluid Transport through Carbon Nanochannels Induced by COOH Functionalization: Implications for Nanofiltration and Oil Recovery

Fluid transport on confined systems is a subject of theoretical and technological interest. For instance, remarkable high flow rates have been obtained in carbon nanochannels (CNs) which cannot be predicted by standard macroscopic theories. Natural rocks, which are at the heart of the shale hydrocarbon revolution, may also exhibit similar properties as the porous structure is mainly at the nanoscale and is carbon rich. Among other differences with CNs, the surfaces are not atomically smooth, as they have organic functional groups anchored on their inner porous surfaces. In this work, we assess the effects of carboxylic functionalization of the nanochannel surfaces on fluid transport. We consider water and methane as representative cases for polar/non-polar fluids and also mixtures of them. We find that the presence of only a few carboxylic groups on the CN causes a large reduction of flow rates for all fluids considered due to the associated geometrical distortion. However, for water, the hydrophilicity induced by the carboxylic functionalization causes not only a dramatic reduction in flow rates but also structural changes in which COOH groups act as nucleation centers for water droplets. Implications of our results show that the flow rates depend on the O/C ratio of the nanochannel, which is a measure of kerogen maturity. The relationship between rock permeability and maturity may provide a way to identify high conductive zones for hydrocarbon recovery. Another application is the possible use of chemical additives to enhance hydrocarbon flow on kerogen-rich rocks. The presence of a small amount of scattered organic functional groups in the nanochannel helps to distribute water molecules along the nanochannel walls, opening a path for hydrocarbon to flow.

Cyclodextrin Polymers as Delivery Systems for Targeted Anti-Cancer Chemotherapy

In the few last years, nanosystems have emerged as a potential therapeutic approach to improve the efficacy and selectivity of many drugs. Cyclodextrins (CyDs) and their nanoparticles have been widely investigated as drug delivery systems. The covalent functionalization of CyD polymer nanoparticles with targeting molecules can improve the therapeutic potential of this family of nanosystems. In this study, we investigated cross-linked γ- and β-cyclodextrin polymers as carriers for doxorubicin (ox) and oxaliplatin (Oxa). We also functionalized γ-CyD polymer bearing COOH functionalities with arginine-glycine-aspartic or arginine moieties for targeting the integrin receptors of cancer cells. We tested the Dox and Oxa anti-proliferative activity in the presence of the precursor polymer with COOH functionalities and its derivatives in A549 (lung, carcinoma) and HepG2 (liver, carcinoma) cell lines. We found that CyD polymers can significantly improve the antiproliferative activity of Dox in HepG2 cell lines only, whereas the cytotoxic activity of Oxa resulted as enhanced in both cell lines. The peptide or amino acid functionalized CyD polymers, loaded with Dox, did not show any additional effect compared to the precursor polymer. Finally, studies of Dox uptake showed that the higher antiproliferative activity of complexes correlates with the higher accumulation of Dox inside the cells. The results show that CyD polymers could be used as carriers for repositioning classical anticancer drugs such as Dox or Oxa to increase their antitumor activity.

Nanocrystalline cellulose derived from melon seed shell (Citrullus colocynthis L.) for reduction and stabilization of silver nanoparticles: Synthesis and catalytic activity

Melon seed shells (MSS) are a hazard to the environment as they host disease vectors. To alleviate the effect, we explored melon seed shells (MSS) as a new source of nanocrystalline cellulose (NCC) with reducing- and stabilizing capacity for the synthesis of silver nanoparticles (AgNPs). The isolation of NCC from discarded MSS served the dual purpose of a reducing- and stabilizing agent in the synthesis of AgNPs. The isolated needle-like crystals (MSS-NCC) had a mean length 204 nm, width 7 nm and aspect ratio 30. The NCC had crystallinity index of 94% with surface rich in –OH and –COOH functionality. The obtained AgNPs covered the surface of the MSS-NCC and catalysed the reduction of nitrobenzene to aniline using NaBH4. The process of the reduction monitored via UV-vis spectroscopy was completed within 12 min. with a rate constant 0.04 min−1 as revealed by the kinetic study.