Charged Molecules Research Articles

Probing the heterogeneity of molecular level organization of ionic liquids: a comparative study using neutral Nile red and cationic Nile blue sulfate as fluorescent probes for butyrolactam-based protic ionic liquids.

Ionic liquids (ILs) are liquid salts composed of cations and anions, known for their significant local heterogeneity at the molecular level. To understand the microheterogeneity with regard to their local polarity and local viscosity, we have used two structurally similar but chemically distinguishable fluorescent probes: Nile red (NR), a neutral molecule, and Nile blue sulfate (NBS), a charged molecule. A comparative study of the response of the two probes to the molecular level heterogeneity of ILs is expected to provide a better clarity of understanding regarding the charged polar domain and the uncharged hydrophobic domain of ILs. Towards this, we synthesized two butyrolactam-based protic ionic liquids (PILs), i.e., BTF and BTD, with the same ionic headgroup ([BT]+) and different alkyl tails ([RCOO]-), where {R = H, C11H23}. BTF has no significant hydrophobic domain, whereas BTD has a larger hydrophobic domain. Temperature-dependent fluorescence parameters such as fluorescence intensity, lifetime, and anisotropy were measured for both NR and NBS molecules. The use of a pair of structurally similar but ionically different probes enables differential estimation of parameters like the microviscosity of a domain using the fluorescence anisotropy parameter (r). The absorption and emission spectra of both probe molecules are observed to be blue shifted upon going from BTF to BTD. NR showed a significant blue shift in absorption and emission band maxima. Conversely, NBS exhibited a small wavelength shift, possibly influenced by the preferred location of their charged head group domain. Temperature-dependent rotational relaxation time (θ) of NR in BTD is smaller than that of NBS by 60-70%, indicating that stronger charge-charge interactions exist between the polar domain of BTD and NBS. Moreover, it is observed that the local viscosity of the BTF IL around both probes is similar, whereas there is a considerable difference for the BTD IL. These results are an indication that NBS being charged prefers to locate itself in the charged head group region of the IL, whereas NR being neutral tends to reside both in the hydrophobic domain and in the head group but is predominantly located in the hydrophobic domain.

Monitoring the response of a model protocell to dye and surfactant molecules through second harmonic generation and fluorescence imaging.

Probing the interaction between molecules and protocells is crucial for understanding the passive transport of functional molecules in and out of artificial and real cells. Second-harmonic generation (SHG) has been proven to be a powerful method for analyzing the adsorption and cross-membrane transport of molecules on lipid bilayers. In this study, we used SHG and two-photon fluorescence (TPF) imaging to study the interaction of charged dye molecules (D289) with a lipid vesicle. Unexpectedly, it was observed that the transport of D289 at a relatively high concentration is not as efficient as that at a lower dye concentration. Periodic shrinking of the model protocell and discharging of D289 out from the vesicle were revealed by combined analyses of SHG and TPF images. The response of the vesicle to a surfactant was also analyzed with D289 as a probe. This work demonstrates that the combined SHG and TPF imaging method is a unique approach that can provide detailed information on the interaction of molecules and lipids (both morphology and molecular kinetics). Determining these subtle interfacial kinetics in molecules is important for understanding the mechanism of many biophysical processes occurring on lipids.

Eu MOF-enhanced FeNCD nanozymes for fluorescence and highly sensitive colorimetric detection of tetracycline.

The constrained enzymatic activity and aggregation challenges encountered by small-sized nanozymes pose obstacles to their practical utility, necessitating a strategy to mitigate aggregation and boost enzymatic catalytic efficiency. In this work, a negatively charged Eu MOF was utilized as the encapsulation matrix, encapsulating the small-sized nanozymes FeNCDs into the Eu MOF to synthesize an FeNCDs@Eu MOF. The dispersibility of the encapsulated FeNCDs was increased, and owing to the negative charge of the FeNCDs@Eu MOF, electrostatic pre-concentration of the positively charged target molecule tetracycline (TC) was facilitated, thereby amplifying the enzymatic catalytic efficiency of the FeNCDs. The response of the FeNCDs to TC increased by nearly 6 times upon encapsulation. The TC detection limit (LOD) of the FeNCDs@Eu MOF-based sensor is as low as 11.63 nM. The incorporation of fluorescence detection expanded the linear range of the sensor, rendering it more suitable for practical sample detection.

Cellular uptake and viability switching in the properties of lipid coated carbon quantum dots for potential bioimaging and therapeutics.

Carbon quantum dots derived from mango leaves exhibited red fluorescence. These negatively charged particles underwent coating with the positively charged lipid molecule N-[1-(2,3-dioleyloxy)propyl]-N,N,N-trimethylammonium chloride (DOTMA). However, the bioconjugate displayed reduced uptake compared to the standalone mQDs in cancer cells (SUM 159A), and increased uptake in case of non-cancerous (RPE-1) cells. Upon in vitro testing, the bioconjugate demonstrated a mitigating effect on the individual toxicity of both DOTMA and mQDs in SUM-159 (cancerous cells). Conversely, it exhibited a proliferative effect on RPE-1 (normal cells).

Delivery of siRNAs Against Selective Ion Channels and Transporter Genes Using Hyaluronic Acid-coupled Carbonate Apatite Nanoparticles Synergistically Inhibits Growth and Survival of Breast Cancer Cells.

Dysregulated calcium homeostasis and consequentially aberrant Ca2+ signalling could enhance survival, proliferation and metastasis in various cancers. Despite rapid development in exploring the ion channel functions in relation to cancer, most of the mechanisms accounting for the impact of ion channel modulators have yet to be fully clarified. Although harnessing small interfering RNA (siRNA) to specifically silence gene expression has the potential to be a pivotal approach, its success in therapeutic intervention is dependent on an efficient delivery system. Nanoparticles have the capacity to strongly bind siRNAs. They remain in the circulation and eventually deliver the siRNA payload to the target organ. Afterward, they interact with the cell surface and enter the cell via endocytosis. Finally, they help escape the endo-lysosomal degradation system prior to unload the siRNAs into cytosol. Carbonate apatite (CA) nanocrystals primarily is composed of Ca2+, carbonate and phosphate. CA possesses both anion and cation binding domains to target negatively charged siRNA molecules. Hybrid CA was synthesized by complexing CA NPs with a hydrophilic polysaccharide - hyaluronic acid (HA). The average diameter of the composite particles was determined using Zetasizer and FE-SEM and their zeta potential values were also measured. The stronger binding affinity and cellular uptake of a fluorescent siRNA were observed for HA-CA NPs as compared to plain CA NPs. Hybrid CA was electrostatically bound individually and combined with three different siRNAs to silence expression of calcium ion channel and transporter genes, TRPC6, TRPM8 and SLC41A1 in a human breast cancer cell line (MCF-7) and evaluate their potential for treating breast cancer. Hybrid NPs carrying TRPC6, TRPM8 and SLC41A1 siRNAs could significantly enhance cytotoxicity both in vitro and in vivo. The resultant composite CA influenced biodistribution of the delivered siRNA, facilitating reduced off target distribution and enhanced breast tumor targetability.

Polyamines (PAs) but not small peptides with closely spaced positively charged groups interact with DNA and RNA, but they do not represent a relevant buffer system at physiological pH values.

Polyamines (PAs) including putrescine (PUT), spermidine (SPD) and spermine (SPM) are small, versatile molecules with two or more positively charged amino groups. Despite their importance for almost all forms of life, their specific roles in molecular and cellular biology remain partly unknown. The molecular structures of PAs suggest two presumable biological functions: (i) as potential buffer systems and (ii) as interactants with poly-negatively charged molecules like nucleic acids. The present report focuses on the question, whether the molecular structures of PAs are essential for such functions, or whether other simple molecules like small peptides with closely spaced positively charged side chains might be suitable as well. Consequently, we created titration curves for PUT, SPD, and SPM, as well as for oligolysines like tri-, tetra-, and penta-lysine. None of the molecules provided substantial buffering capacity at physiological intracellular pH values. Apparently, the most important mechanism for intracellular pH homeostasis in neurons is not a buffer system but is provided by the actions of the sodium-hydrogen and the bicarbonate-chloride antiporters. In a similar approach we investigated the interaction with DNA by following the extinction at 260 nm when titrating DNA with the above molecules. Again, PUT and tri-lysine were not able to interact with herring sperm DNA, while SPD and SPM were. Obviously, the presence of several positively charged groups on its own is not sufficient for the interaction with nucleic acids. Instead, the precise spacing of these groups is necessary for biological activity.

Microscopically segregated ligand distribution in co-assembled peptide-amphiphile nanofibers.

Peptide amphiphiles (PAs) self-assemble into cylindrical nanofibers with applications in protein purification, tissue engineering, and regenerative medicine. For these applications, functionalized PAs are often co-assembled with oppositely charged filler PAs. Finding the conditions at which these fibers are homogeneously mixed or segregated is crucial for the required application. We co-assemble negative C12VVEE fillers and positive C12VVKK-OEG4-Z33 ligands, which are important for antibody purifications. Our results show that the ligands tend to cluster and locally segregate in the fiber surfaces. The Z33s are overall neutral and form large aggregates in bulk solution due to short range attractions. However, full segregation of the C12VVKK-OEG4-Z33 is not observed in the cylindrical surface due to the electrostatic penalty of forming large domains of similarly charged molecules. This is commensurate with previous theoretical predictions, showing that the competition between short-range attractive interactions and long-range electrostatic repulsions leads to pattern formation in cylindrical surfaces. This work offers valuable insight into the design of functionalized nanofibers for various biomedical and chemical applications.

Engineered human H-chain ferritin with reversed charge of the internal cavity exhibits RNA-mediated spongelike effect for loading RNA/DNA-binding molecules.

Ferritins are globular proteins with an internal cavity that enables the encapsulation of a plethora of low-mass compounds. Unfortunately, the overall negative surface charge of ferritin's internal cavity hampers efficient loading of negatively charged molecules. Therefore, we produced a genetically engineered human H-chain ferritin containing a cationic RKRK domain, reversing the natural net charge of the cavity to positive, thus allowing for efficient encapsulation of negatively charged siRNA. Due to the reversed, positive charge mediated by RKRK domains, the recombinant ferritin produced in E. coli inherently carries a load of bacterial RNA inside its cavity, turning the protein into an effective sponge possessing high affinity for DNA/RNA-binding substances that can be loaded with markedly higher efficiency compared to the wildtype protein. Using doxorubicin as payload, we show that due to its loading through the RNA sponge, doxorubicin is released in a sustained manner, with a cytotoxicity profile similar to the free drug. In summary, this is the first report demonstrating a ferritin/nucleic acid hybrid delivery vehicle with a broad spectrum of properties exploitable in various fields of biomedical applications.

Formulation of Drug-polyelectrolyte Complex for Enhancement of Solubility of Hydrochlorthiazide

ABSTRACT: The objective of this work is to formulate Nanoplex formulation which enhances the drug solubility and also to enhance the dissolution rate of the formulation which were prepared. Complex nanoplex is formed when positively or negatively charged molecules of the drug react with oppositely charged polyelectrolyte. In this study, we use hydrochlorothiazide as a study drug and dextran sulphate as anionic polyelectrolyte. During the procedure crystalline nanoplex is formed due to electrostatic interactions between API and polyelecrolyte. The nanoplex shaped by this method upgrades dissolvability and disintegration rate of inadequately water solvent medication. It was assessed for complexation effectiveness, % yield, molecule size, zeta potential, SEM, TEM, XRD, soaked solvency study and so forth. This gives particles having molecule size in the scope of 100-200nm.Amongst different ratio, 1:1 showed highest Complexation efficiency as 96.3%, % yield and drug loading as 82 % and 77.69 % respectively. Solubility and stability of hydrochlorothiazide, poorly water-soluble molecule can be increased with formulation of hydrochlorothiazide nanoplex.

Power and Sensitivity Management of Carbon Nanotube Transistor Glucose Biosensors.

Continuous glucose monitoring (CGM), which is significant for the daily management of diabetes, requires a low-power-consumption sensor system that can track low nanomolar levels of glucose in physiological fluids, such as sweat and tears. However, traditional electrochemical methods are limited to analytes in micromolar to millimolar ranges and entail high power consumption. Carbon nanotube (CNT) film field-effect transistors (FETs) are promising for constructing extremely sensitive biosensors, but their wide applications in CGM are limited by the strong screening effect of physiological fluids and the zero charge of glucose molecules. In this study, we demonstrate a glucose aptamer-modified CNT FET biosensor to realize a highly sensitive CGM system with sub-nW power consumption by applying a suitable gate voltage. A positive gate voltage can enlarge the effective Debye screening length at the double layer to reduce the local ion population nearby and then improve the sensitivity of the FET-based biosensors by 5 times. We construct CNT FET sensors for CGM with a limit of detection of 0.5 fM, a record dynamic range up to 109, and a power consumption down to ∼100 pW. The proposed field-modulated sensing performance scheme is applicable to other aptamer-based FET biosensors for detecting neutral or less charged molecules and opens opportunities to develop facilely modulated, highly sensitive, low-power, and noninvasive CGM systems.

Smart hybrid copolymer-coated silica nanosystems with dual responsiveness as a carrier for positive charged molecules

Smart nanosystems consisting of inorganic particles and responsive polymers display significant and remarkable aspects. Such combined work exploits a facile path for multifunctional nanomaterials and facilitates various novel technological applications due to “live” polymer components. Here, we report the design and synthesis of a new platform of smart hybrid nanosystems (SHN) for positively charged probe loading and specific release under pH and temperature-controlled conditions. The SHN was prepared by a simple sequential method that produced an integrated core–shell nanomaterial with a dual stimulus response and excellent colloidal stability. Further, we demonstrate by crossing DLS and NMR results that these core–shell nanosystems present transduction from both stimuli to a mechanical shrinkage of the polymeric shell, leading to a remote-controlled dual response that can be synthetically tuned by controlling the molar ratio between monomers. Finally, we studied the potential of these SHN as molecular carriers and demonstrated that they are useful for selective ionic encapsulation of positively charged molecules, which release is controlled by the dual responsiveness. We successfully extended this concept to doxorubicin release triggered by T and pH changes, which opens possibilities of using these SHN improving results and patient compliance in chemotherapy treatments.

Constructing robust and anti-fouling superwettable membrane with layer-by-layer assembly of Fe(OH)3 colloid

Layer-by-layer (LBL) assembly method, with the advantages of simple operation and strong universality, has attracted much attention recently. However, the weak molecule-to-molecule and molecule-to-ion interactions have limited its development. During this work, the molecule-to-solid interaction was adopted and a robust LBL coating was achieved by alternately depositing positively charged Fe(OH)3 colloids and negatively charged sodium alginate molecules. The molecule-to-solid interaction could continuously regenerate under corrosive conditions due to water insolubility and the chemical stability of solids. When the electrostatic interaction was broken, the abundant chemically stable solids acted as anchors to immobilize the soluble molecules and maintain the stability of the LBL coating. The prepared superwettable membranes exhibited superior oil-in-water emulsion separation efficiency, anti-fouling properties, and chemical stability. Meanwhile, the separation performance survived one week's harsh environments of strong acid and alkali.

SiRNA Delivery from Cationic Nanocarriers Prepared by Diffusion-assisted Loading in the Presence and Absence of Electrostatic Interactions.

In this study, we use modified cationic nanocarriers as vehicles for the intracellular delivery of therapeutic siRNA. After developing nanocarrier formulations with appropriate pKa, size, swellability, and cytocompatibility, we investigated the importance of siRNA loading methods by studying the impact of the pH and time over which siRNA is loaded into the nanocarriers. We concentrate on diffusion-based loading in the presence and absence of electrostatic interactions. siRNA release kinetics were studied using samples prepared from nanocarriers loaded by both mechanisms. In addition, siRNA delivery was evaluated for two formulations. While previous studies were conducted with samples prepared by siRNA loading at low pH values, this research provides evidence that loading conditions of siRNA affect the release behavior. This study concludes that this concept could prove advantageous for eliciting prolonged intracellular release of nucleic acids and negatively charged molecules, effectively decreasing dose frequency and contributing to more effective therapies and improved patient outcomes. In addition, our findings could be leveraged for enhanced control over siRNA release kinetics, providing novel methods for the continued optimization of cationic nanoparticles in a wide array of RNA interference-based applications.

Development of polyethersulfone/polylactic acid‐blended nanocellulose membranes for enhanced removal of methylene blue dye

AbstractHerein, adsorptive polyethersulfone/polylactic acid (PES/PLA) blends membranes with systematic concentrations of cellulose nanofibers (CNFs) (0.5–2.5 wt%) were developed via a modified phase inversion process for the enhanced removal of cationic methylene blue (MB) dye. To the best of our knowledge, this is the first time that such adsorptive membranes have been produced for potential use in wastewater treatment. The fabricated membranes were characterized for surface and cross‐sectional morphology (scanning electron microscope), surface roughness (atomic force microscope), functionality (Fourier‐transform infrared spectroscopy), thermal stability (thermal gravimetric analysis), wettability (contact angle measurements), antifouling behavior (flux recovery studies), and dye adsorption and reusability (adsorption and desorption tests). CNF incorporated membranes showed improved wetting properties, with contact angle decreasing from 76° in the pristine membranes to 48° in 2.5 wt% PES/PLA membranes. The membrane bulk porosity increased from 60.3% to 79.23%, while the pure water flux increased from 210.8 to 399.12 Lm−2 h−1. At optimal conditions, CNF‐modified membranes removed >98% of MB compared with 8% removal by the pristine membranes. After five cycles of adsorption and desorption, the membrane with 2 wt% CNFs achieved over 70% dye removal showing excellent reusability properties. Adsorption followed pseudo‐second‐order and Freundlich models. The adsorption was attributed to electrostatic interactions between the negatively charged membrane surfaces and the positively charged dye molecules as well as through hydrogen bonding. Therefore, this work revealed that CNF‐modified PES/PLA membranes can be used as adsorbents for the enhanced removal of organic pollutants in water treatment applications.

Interplay of Adsorption Geometry and Work Function Evolution at the TCNE/Cu(111) Interface.

The adsorption of organic electron acceptors on metal surfaces is a powerful way to change the effective work function of the substrate through the formation of charge-transfer-induced dipoles. The work function of the interfaces is hence controlled by the redistribution of charges upon adsorption of the organic layer, which depends not only on the electron affinity of the organic material but also on the adsorption geometry. As shown in this work, the latter dependence controls the work function also in the case of adsorbate layers exhibiting a mixture of various adsorption geometries. Based on a combined experimental (core-level and infrared spectroscopy) and theoretical (density functional theory) study for tetracyanoethylene (TCNE) on Cu(111), we find that TCNE adsorbs in at least three different orientations, depending on TCNE coverage. At low coverage, flat lying TCNE dominates, as it possesses the highest adsorption energy. At a higher coverage, additionally, two different standing orientations are found. This is accompanied by a large increase in the work function of almost 3 eV at full monolayer coverage. Our results suggest that the large increase in work function is mainly due to the surface dipole of the free CN groups of the standing molecules and less dependent on the charge-transfer dipole of the differently oriented and charged molecules. This, in turn, opens new opportunities to control the work function of interfaces, e.g., by synthetic modification of the adsorbates, which may allow one to alter the adsorption geometries of the molecules as well as their contributions to the interface dipoles and, hence, the work function.

An electrochemical biosensor to assay Trop-2 of breast cancer cells fabricated by methylene blue-assisted assembly of DNA nanoparticles

Human trophoblast surface cell antigen 2 (Trop-2) on the tumor cell membrane can not only serve as the target for chemotherapy drugs, but also as a biomarker for typing and prognosis of breast cancer; however, assay of Trop-2 is seriously hampered due to the limitations of available tool. Herein, we have designed and fabricated an electrochemical biosensor for the assay of Trop-2 based on methylene blue (MB)-assisted assembly of DNA nanocomposite particles (DNPs). Specially, the recognition between Trop-2 and its aptamer may activate the primer exchange reaction (PER) on an electrode surface to produce long single-strand DNA (ssDNA) which can be self-assembled into DNPs by electrostatic interaction between negative charged DNA and positive charged and electro-active MB molecules which can also be used to give electrochemical signal. By using this electrochemical biosensor, ultrasensitive detection of tumor cells with high Trop-2 expressions can be conducted, with the limit of detection (LOD) of 1 cell/mL. Moreover, this biosensor can be further used for accurately profiling Trop-2 expression of tumor cells in mouse tissues, suggesting its great potential in the precise definition of breast cancer.

Strategies of chemolithoautotrophs adapting to high temperature and extremely acidic conditions in a shallow hydrothermal ecosystem

BackgroundActive hydrothermal vents create extreme conditions characterized by high temperatures, low pH levels, and elevated concentrations of heavy metals and other trace elements. These conditions support unique ecosystems where chemolithoautotrophs serve as primary producers. The steep temperature and pH gradients from the vent mouth to its periphery provide a wide range of microhabitats for these specialized microorganisms. However, their metabolic functions, adaptations in response to these gradients, and coping mechanisms under extreme conditions remain areas of limited knowledge. In this study, we conducted temperature gradient incubations of hydrothermal fluids from moderate (pH = 5.6) and extremely (pH = 2.2) acidic vents. Combining the DNA-stable isotope probing technique and subsequent metagenomics, we identified active chemolithoautotrophs under different temperature and pH conditions and analyzed their specific metabolic mechanisms.ResultsWe found that the carbon fixation activities of Nautiliales in vent fluids were significantly increased from 45 to 65 °C under moderately acidic condition, while their heat tolerance was reduced under extremely acidic conditions. In contrast, Campylobacterales actively fixed carbon under both moderately and extremely acidic conditions under 30 − 45 °C. Compared to Campylobacterales, Nautiliales were found to lack the Sox sulfur oxidation system and instead use NAD(H)-linked glutamate dehydrogenase to boost the reverse tricarboxylic acid (rTCA) cycle. Additionally, they exhibit a high genetic potential for high activity of cytochrome bd ubiquinol oxidase in oxygen respiration and hydrogen oxidation at high temperatures. In terms of high-temperature adaption, the rgy gene plays a critical role in Nautiliales by maintaining DNA stability at high temperature. Genes encoding proteins involved in proton export, including the membrane arm subunits of proton-pumping NADH: ubiquinone oxidoreductase, K+ accumulation, selective transport of charged molecules, permease regulation, and formation of the permeability barrier of bacterial outer membranes, play essential roles in enabling Campylobacterales to adapt to extremely acidic conditions.ConclusionsOur study provides in-depth insights into how high temperature and low pH impact the metabolic processes of energy and main elements in chemolithoautotrophs living in hydrothermal ecosystems, as well as the mechanisms they use to adapt to the extreme hydrothermal conditions.4ap83QbxwyKb6GHBwDJLyuVideo

Influence of pH on the Inhibiting Characteristics of Cresol Red Incorporated in Chitosan Coatings on Zinc

The present work focuses on the investigation of protective coatings produced on zinc from chitosan (Chit) and an anionic dye, namely cresol red. Cresol red (CR) fulfills the basic requirements to be used as a corrosion inhibitor because it possesses a relatively high molecular weight and includes in its structure oxygen and sulfur atoms as well as aromatic rings. Moreover, it is an anionic compound that can interact with positively charged chitosan to produce reinforced coatings for zinc anti-corrosion protection. The influence of cresol red as a possible corrosion inhibitor for zinc substrates was investigated either in solution or incorporated in Chit coatings. Two preparation methods for the coatings were used: (i) Chit coating impregnation by immersion in the CR solution after Chit deposition on Zn, and (ii) chitosan mixing with the CR solution before applying the dip-coating technique. Potentiodynamic polarization curves were used to determine the kinetic parameters of the corrosion process. Long-term measurements were carried out in wet/dry cyclic conditions by using electrochemical impedance spectroscopy. EIS measurements recorded in 0.2 g/L Na2SO4 at pH = 7 show an important increase in the impedance of the coatings occurring from the first until the fifty-fifth day in a row, in dry–wet cycles. This increase is due to the beneficial effect of CR incorporated in Chitosan and could be, at least partially, related to a consolidation of the Chit coating structure in the presence of CR by crosslinking between Chit and CR molecules. The structure of the coatings was studied, and the interactions between chitosan and cresol red were put into evidence by using FT-IR spectroscopy. Adhesion and wettability measurements were also carried out. The adhesion of Chit incorporating CR on Zn was better than that on glass substrates and reached ~99.99%, suggesting a better affinity of the chitosan coating towards the Zn substrate due to the existence of ZnO on the substrate surface. All the results show that CR could be used on zinc as a corrosion inhibitor incorporated in chitosan at basic pHs, but without taking advantage of its pH-indicating properties, which are lost due to the interactions occurring between the positively charged biopolymer and the negatively charged dye molecule. The preparation method of Chit coating impregnation with CR by immersion in the solution after deposition on Zn led to poorer results than the method in which chitosan was previously mixed with CR before applying the dip-coating technique.

Functionalized graphite carbon nitride nanofluid membranes for enhanced osmotic energy harvesting

Reverse electrodialysis is a promising technology that using ion exchange membrane to obtain electrical energy directly between seawater and river water. Current attempts that based on the ion exchange membrane are limited due to the channel size and low charge density. Graphitic carbon nitride (g-C3N4, GCN) is a type of graphite-layered polymer that combined with inherent nanopore structure and adjustable surface charge, which provides a shortcut for the preparation of highly selective ion exchange membrane. However, carbon nitride membranes still exhibit low power density. Herein, g-C3N4 was successfully functionalized with three different negatively charged molecules (carboxylation, polyacrylic acid (PAA) and poly (sodium 4-styrenesulfonare) (PSS)), which benefited from its rich nitrogen-containing groups. These functionalized g-C3N4 were combined with anodized aluminum oxide (AAO) membrane to form heterochannel membranes, which can transport counter-ions and harvest osmotic energy. The results showed that the surface charge density of functionalized g-C3N4 was obviously improved, which enhanced the output power density. Among them, the heterochannel membrane functionalized with PSS (PSS-CN/AAO) had the highest output power density of 31 mW/m2 (effective area 4.9 mm2), which was 3.1 times higher than that of the unfunctionalized heterochannel membrane (GCN/AAO, 9 mW/m2). In this base, two-dimensional PSS-CN/ANF membranes were designed by compositing PSS-functionalized g-C3N4 (PSS-CN) nanosheets with aramid nanofiber (ANF), which can maintain high output power density (50 mW/m2) and further improve the mechanical property of membrane, providing a guarantee for the long-term stable use of nanofluid membrane.

Controlled electroactive release from solid-state conductive elastomer electrodes

This work highlights the development of a conductive elastomer (CE) based electrophoretic platform that enables the transfer of charged molecules from a solid-state CE electrode directly to targeted tissues. Using an elastomer-based electrode containing poly (3,4-ethylenedioxythiophene) nanowires, controlled electrophoretic delivery of methylene blue (MB) and fluorescein (FLSC) was achieved with applied voltage. Electroactive release of positively charged MB and negatively charged FLSC achieved 33.19 ± 6.47 μg release of MB and 22.36 ± 3.05 μg release of FLSC, a 24 and 20-fold increase in comparison to inhibitory voltages over 1 h. Additionally, selective, and sequential release of the two oppositely charged molecules from a single CE device was demonstrated, showing the potential of this device to be used in multi-drug treatments.