Aqueous Methylene Blue Research Articles

Boosted photocatalytic performance of cobalt ferrite anchored g-C3N4 nanocomposite toward various emerging environmental hazardous pollutants degradation: insights into stability and Z-scheme mechanism.

In this study, a highly efficient CoFe2O4-anchored g-C3N4 nanocomposite with Z-scheme photocatalyst was developed by facile calcination and hydrothermal technique. To evaluate the crystalline structure, sample surface morphology, elemental compositions, and charge conductivity of the as-synthesized catalysts by various characterization techniques. The high interfacial contact of CoFe2O4 nanoparticles (NPs) with g-C3N4 nanosheets reduced the optical bandgap from 2.67 to 2.5eV, which improved the charge carrier separation and transfer. The photo-degradation of methylene blue (MB) and rhodamine B (Rh B) aqueous pollutant suspension under visible-light influence was used to investigate the photocatalytic degradation activity of the efficient CoFe2O4/g-C3N4 composite catalyst. The heterostructured spinel CoFe2O4 anchored g-C3N4 photocatalysts (PCs) with Z-scheme show better photocatalytic degradation performance for both organic dyes. Meanwhile, the efficiency of aqueous MB and Rh B degradation in 120 and 100min under visible-light could be up to 91.1% and 73.7%, which is greater than pristine g-C3N4 and CoFe2O4 catalysts. The recycling stability test showed no significant changes in the photo-degradation activity after four repeated cycles. Thus, this work provides an efficient tactic for the construction of highly efficient magnetic PCs for the removal of hazardous pollutants in the aquatic environment.

Synthesis of a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin.

Porphyrin compound-based photochemical molecules and biomaterials have been synthesized for photosensitivity and bioimaging experiments. However, most porphyrin photosensitizers have limited application in biological environments owing to severe aggregation in aqueous solutions. In the present study, we prepared amphipathic and photosensitive copolymers using zinc porphyrin via consecutive atom transfer-free radical polymerizations (ATRPs) comprising photoresponsive and thermosensitive chain segments. Furthermore, we evaluated the photocatalytic activity of the copolymer for methylene blue (MB) in water. Methods: First, we synthesized a photoresponsive ain segment of poly (6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate) (ZnPor-PAzo); then, ZnPor-PAzo was used as a macroinitiator and was polymerized with N-isopropylacrylamide (NIPAM) via ATRPs to obtain a novel photochemical and thermoresponsive diblock biomaterial with end-functionalized zinc porphyrin [(ZnPor-PAzo)-PNIPAMs]. Results: The polydispersity index (M w/M n) of (ZnPor-PAzo)-PNIPAMs was 1.19-1.32. Furthermore, its photoresponsive and thermosensitive characteristics were comprehensively studied. Discussion: The end-functionalized diblock copolymer (ZnPor-PAzo)-PNIPAM exhibits obvious fluorescence and efficient photocatalytic activity for aqueous MB under visible light.

Impact of Methylene Blue on Enhancing the Hydrocarbon Potential of Early Cambrian Khewra Sandstone Formation from the Potwar Basin, Pakistan.

Significant amounts of hydrocarbon resources are left behind after primary and secondary recovery processes, necessitating the application of enhanced oil recovery (EOR) techniques for improving the recovery of trapped oil from subsurface formations. In this respect, the wettability of the rock is crucial in assessing the recovery and sweep efficiency of trapped oil. The subsurface reservoirs are inherently contaminated with organic acids, which renders them hydrophobic. Recent research has revealed the significant impacts of nanofluids, surfactants, and methyl orange on altering the wettability of organic-acid-contaminated subsurface formations into the water-wet state. This suggests that the toxic dye methylene blue (MB), which is presently disposed of in huge quantities and contaminates subsurface waters, could be used in EOR. However, the mechanisms behind hydrocarbon recovery using MB solution for attaining hydrophilic conditions are not fully understood. Therefore, the present work examines the impacts of MB on the wettability reversal of organic-acid-contaminated Khewra sandstone samples (obtained from the outcrop in the Potwar Basin, Pakistan) under the downhole temperature and pressure conditions. The sandstone samples are prepared by aging with 10-2 mol/L stearic acid and subsequently treated with various amounts of aqueous MB (10-100 mg/L) for 1 week. Contact angle measurements are then conducted under various physio-thermal conditions (0.1-20 MPa, 25-50 °C, and salinities of 0.1-0.3 M). The results indicate that the Khewra sandstone samples become hydrophobic in the presence of organic acid and under increased pressure, temperature, and salinity. However, the wettability changes from oil-wet to preferentially water-wet in the presence of various MB solutions, thus highlighting the favorable effects of MB on EOR from the Khewra sandstone formation. Moreover, the most significant change in wettability is observed for the Khewra sandstone sample that was aged using 100 mg/L MB. These results suggest that injecting MB into deep underground Khewra sandstone reservoirs may produce more residual hydrocarbons.

Utilizing sequence transformation of selective copper metal as an efficient heterogeneous Fenton-like catalyst for the degradation of aqueous methylene blue

Utilizing sequence transformation of selective copper metal as an efficient heterogeneous Fenton-like catalyst for the degradation of aqueous methylene blue

Adsorption investigation of a composite of metal-organic framework and polyethylene oxide hydrogel

Though adsorption techniques are eco-environmentally friendly, most lack the effectiveness of complete contaminant elimination leading to increasing concerns about the presence of aqueous contaminants on humans. Thus, synergistic combination of low adsorption capacity adsorbents may be an effective method to enhance their aqueous contaminant uptake. Sol-gel synthesized lanthanum-1,4-benzene dicarboxylate metal organic framework (LaBDC MOF) and polyethylene oxide (PEO) hydrogel were combined to prepare a synergistic composite adsorbent (PEO-LaBDC) for aqueous methylene blue (MB) adsorption. Major properties of the pristine LaBDC MOF and PEO hydrogel were expressed in the characterized composite indicating successful preparation. PEO-LaBDC composite MB removal rate of MB was at least twice as fast (60 min) to those of the pristine LaBDC MOF (120 min) and PEO hydrogel (125 min). The fitting of kinetics model was fractal in nature, and optimum adsorption was on the alkaline end of the pH spectrum for all adsorbents (pH = 12, 10, and 10, respectively). Comparatively, the composite exhibited a better adsorption performance of ≈177% higher than the pristine LaBDC MOF; buttressing the idea that synergistic combination of adsorbents in composites could enhance adsorption processes. Therefore, the PEO-LaBDC composite is a promising adsorbent for the remediation of aqueous MB.

Supercritical CO2‐assisted formation of metal–organic framework‐loaded porous polystyrene membranes for dye removal

AbstractMetal–organic frameworks (MOFs) are efficient adsorbents for the removal of hazardous materials. An MOF based on 1,3,5‐benzenetricarboxylic acid (BTC), Cu3(BTC)2, is prepared via phase separation using supercritical CO2 (scCO2) as a nonsolvent for the polymer solution. The prepared MOF is then loaded onto microporous polystyrene membranes. To evaluate the performance of Cu3(BTC)2‐loaded microporous polystyrene membranes for pollutant removal from water, they are tested for the separation of methylene blue (MB) dye from an aqueous solution. Prior to the preparation of the Cu3(BTC)2‐loaded microporous polystyrene membranes, Cu3(BTC)2 is activated with scCO2. After the activation with scCO2, the internal surface area of Cu3(BTC)2 and its MB adsorption increase. A toluene solution of polystyrene containing Cu3(BTC)2 particles is prepared, and scCO2 is introduced to induce the phase separation of the polymer solution. A Cu3(BTC)2‐loaded microporous polystyrene membrane is obtained without the collapse of the structure after the release of the CO2 pressure. MB can be readily and rapidly removed from aqueous solutions using Cu3(BTC)2‐loaded microporous polystyrene membranes. The removal efficiencies for aqueous MB solution were high, and removal efficiencies reached 92.8%.

Photocatalytic degradation of aqueous methylene blue using ca-alginate supported ZnO nanoparticles: point of zero charge role in adsorption and photodegradation.

A novel insoluble Ca-Alginate created from soluble Na-Alginate was used as a support substrate for ZnO nanoparticles producing ZnO@Ca-Alginate composite photocatalyst. Fourier Transform Infrared (FT-IR), Ultraviolet-Visible (UV-Vis), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Diffraction (XRD) analysis techniques were used in the characterization of the prepared ZnO@Ca-Alginate. The ZnO@Ca-Alginate was tested for its potential use in the photodegradation of Methylene Blue (MB) from an aqueous solution under solar-simulated light. This composite photocatalyst efficiency in MB removal was compared with naked ZnO potential considering different conditions and parameters (e.g. pH, MB concentration, amount of photocatalyst, and irradiation time). The MB concentrations were identified using UV-vis spectrophotometric methods. While, high-performance liquid chromatography (HPLC), Total organic carbon (TOC) analysis, and other elemental analyses were used to confirm the MB complete mineralization. The MB photodegradation results were performed by using UV-vis analysis., the results showed that up to 95% of MB (40 mL, 40 ppm) was removed within 30 min of irradiation using either ZnO@Ca-Alginate or naked ZnO. The pH and the zero-charge point (Pzc) values play a main role in the adsorption and photodegradation results. The Pzc values for Ca-Alginate, ZnO, and Zn@Ca-Alginate were 6.5, 8.8, and 6.8 respectively. The prepared composite catalyst showed a maximum adsorption and photodegradation in a basic to slightly basic medium, the MB completely removed at pH of 7.7 within an hour of irradiation. The complete miniralzation of MB at the end of the photodegrdation process was confirmed. Here it is proved that the ZnO@Ca-Alginate photocatalyst can be recovered and reused without any significant decrease in its effectiveness.

Translational Potential of Fluorescence Polarization for Breast Cancer Cytopathology.

Breast cancer is the most common malignancy in women. The standard of care for diagnosis involves invasive core needle biopsy followed by time-consuming histopathological evaluation. A rapid, accurate, and minimally invasive method to diagnose breast cancer would be invaluable. Therefore, this clinical study investigated the fluorescence polarization (Fpol) of the cytological stain methylene blue (MB) for the quantitative detection of breast cancer in fine needle aspiration (FNA) specimens. Cancerous, benign, and normal cells were aspirated from excess breast tissues immediately following surgery. The cells were stained in aqueous MB solution (0.05 mg/mL) and imaged using multimodal confocal microscopy. The system provided MB Fpol and fluorescence emission images of the cells. Results from optical imaging were compared to clinical histopathology. In total, we imaged and analyzed 3808 cells from 44 breast FNAs. Fpol images displayed quantitative contrast between cancerous and noncancerous cells, whereas fluorescence emission images showed the morphological features comparable to cytology. Statistical analysis demonstrated that MB Fpol is significantly higher (p < 0.0001) in malignant vs. benign/normal cells. It also revealed a correlation between MB Fpol values and tumor grade. The results indicate that MB Fpol could provide a reliable, quantitative diagnostic marker for breast cancer at the cellular level.

Preparation and characterization of PEGDE-EDTA-modified magnetic chitosan microsphere as an eco-friendly adsorbent for methylene blue removal

Chitosan has been acknowledged as the emerging prominent pollutant remover with environmentally friendly properties. Herein, we have developed magnetic chitosan (MC) microsphere with functional group enrichment using polyethylene glycol diglycidyl ether (PEGDE) and ethylenediaminetetraacetic acid (EDTA) to remove aqueous methylene blue. The success of the functional group enrichment was proven by the characterization carried out in Fourier transform-infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and Scanning Electron Microscope (SEM) analyses. The adsorption capacity of methylene blue onto the prepared MC increased as much as 37.62% after the addition of EDTA. The optimum adsorption parameters recorded in this study were 30minutes contact time and pH level of 10. At such optimum conditions, the adsorption capacity and removal percentage reached 5.04±0.03 mg/g and 80.64±0.12%, respectively. Adsorption studies using various models revealed that the best fit of experimental data with that of theoretical was generated by the Freundlich model equation (R2 = 0.95283; root-mean-square-errors = 27.22). Exothermic adsorption was observed according to the thermodynamic study (∆H = -124.43 kJ/mol). In conclusion, our adsorbent prepared from green materials and methods could effectively remove the methylene blue from water medium.

Removal of methylene blue using a novel generation photocatalyst based on nano-SnO2/wild plumb kernel shell biochar composite

A series of measurement results revealed that the nano-SnO2 (n-SnO2) nanoparticles were spread uniformly on the carbon surface inside the wild plum (Prunus domestica) kernel shell biochar (WPKSB) structure. The addition of hydrothermally synthesized n-SnO2 to WPKS improved both the adsorption capacity and the photocatalytic potential of WPKSB for methylene blue (MB) removal. When the initial MB content was 5 mg/L, the n-SnO2@WPKSB composite demonstrated high MB removal efficiency under UV light via a combined effect of adsorption and photocatalysis. The n-SnO2@WPKSB composite removed 99.5 (±0.4) % of the MB from the dye-polluted water sample in 105 minutes at pH of 7.0. Because of the synergistic effect of adsorption and photodegradation, the composite was more effective at treating the aqueous MB solution than WPKSB and n-SnO2 alone. Reusability tests were run to remove MB to assess the composite structure’s chemical stability and catalytic capacity. The n-SnO2@WPKSB composite was characterized using X-ray Diffraction, Fourier Transform infrared and Scanning Electron Microscopy. This research investigates how to make metal oxide/biochar nanocomposites with exceptional adsorption and photocatalysis properties for the oxidation and removal of MB.

Facile fabrication of crescentic ZnO nanorod-based photo-catalytic micro-fluidic reactors

With a ZnO nanorod (ZnONR)-coated glass rod in diameter 8 mm inserted into a glass tube in diameter 9 mm and the bare glass rod into the ZnONR-coated inner surface of the glass tube, two types of crescentic ZnONR-based micro-fluidic reactors were readily constructed at a low cost. In presence of ultraviolet (UV) light and at different volume flow rate Q aqueous methylene blue (MB) solution was degraded with the ZnONR-based micro-fluidic reactors hydrothermally synthesized at varied Zn2+ concentration of the growth solution. It is found that the crescent-shaped micro-channel facilitates adequate MB mass-transport and plentiful UV irradiation. The optimal Q exists at which sufficient MB species transport towards and are fully adsorbed on the ZnONRs. The Zn2+ concentration of the growth solution remarkably influences the contact angle (CA) of the ZnONRs and the solid-liquid contact surface area of the ZnONRs with aqueous MB solution, and further the reaction constant K of the micro-fluidic reactors. The largest K values of two kinds of the micro-fluidic reactors were determined to be 1.30 and 1.23 min−1 at both Q value 50 μl/min of aqueous MB solution and Zn2+ concentration 50 mM of the growth solution. The cost-effective crescentic micro-fluidic reactor has potential to be used to photo-degrade other organic pollutants in waste water with high photo-degradation efficiency.

Boosting photocatalytic interaction of sulphur doped reduced graphene oxide-based S@rGO/NiS2 nanocomposite for destruction of pathogens and organic pollutant degradation caused by visible light

Semiconductive materials that are activated by solar light and have a low e- and h+ pair recombination rate, a short bandgap, and fast charge carrier characteristics are effective organic pollution treatment catalysts. Synthesizing sulphur doped reduced graphene oxide/NiS2 ([email protected]/NiS2) nanocomposites (NCs) for effective dye-degradation through photocatalysis under solar irradiation is the subject of this paper. [email protected]/NiS2 NCs were made using a simple and efficient [email protected] nanosheets in NiS2 solution technique. When bound to rGO, NiS2 nanoparticles (NPs) act as an effective catalyst for the removal of methylene blue (MB) dye. SEM, EPR, FTIR, UV–vis, photocurrent responses, XRD, and EDX were used to characterize [email protected]/NiS2 NCs. [email protected]/NiS2 is predominantly utilized as a photocatalyst for photoreaction-based degradation of aqueous MB dye. The nanocomposite removes 96 percent of the MB dye in 84 min. The presence of NiS2 NPs in the catalyst increases the formation of hydroxyl radicals (OH), which supports the photocatalytic process by suppressing electron (e-) and hole (h+) recombination, resulting in the destruction of organic contaminants. The catalyst's effectiveness is further tested by altering the pH of the MB solution medium. The reaction rate is pH dependent, with the quickest degradation time in the presence of [email protected]/NiS2 NCs occurring at pH 8. The reusable catalytic characteristics of suspended [email protected]/NiS2 NCs are investigated for six cycles, yielding a degradation efficiency of more than 93 percent in 84 min. Under sunlight, the antibacterial effectiveness of [email protected]/NiS2 was investigated against Gram-positive and Gram-negative microorganisms. These promising findings could be used to purify polluted water from numerous sectors.

Photo-Fenton activated C3N4x/AgOy@Co1-xBi0.1-yO7 dual s-scheme heterojunction towards degradation of organic pollutants

Fenton-heterojunction photocatalysis is widely applied related to environmental water remediation. Methylene blue (MB) and Oxytetracycline (OTC) were degraded by Fenton-activated catalysts under dark as well as visible light conditions. The C3N4x/AgOy@Co1-xBi1-yO7 was synthesized by the combination of sol-gel and annealing approaches. The synergetic effect of C3N4x/AgOy@Co1-xBi1-yO7 enhanced generation of active sites for photocatalytic degradation resulting in the broadening of visible light absorption efficiency. The photo corrosion of cobalt oxide-based composite was prevented by introduction of silver and graphitic carbon nitride. The prepared composites were used for exploiting photodegradation performance of aqueous MB and OTC solutions. Significant degradation efficiency of 96.4% MB and 93% of OTC was achieved in natural pH in 120 min and 160 min respectively. The degradation potential of C3N4x/AgOy@Co1-xBi1-yO7 is attributed to the lowered recombination rate of electron and hole pairs. The photoluminescent, EIS and band gap studies provided evidence for efficient degradation of MB and OTC. The composite maintained degradation efficiency of 78% and 75% even after four successive cycles. The reusability test confirmed the feasibility of photocatalyst for multiple uses. Besides, scavenger experiment was performed to investigate the role of radicals in the degradation of MB and OTC. Efficient degradation results revealed that C3N4x/AgOy@Co1-xBi1-yO7 is a promising Fenton-like catalyst that can be used for environmental wastewater remediation.

Scale-Up of a Heterogeneous Photocatalytic Degradation Using a Photochemical Rotor-Stator Spinning Disk Reactor.

Many chemical reactions contain heterogeneous reagents, products, byproducts, or catalysts, making their transposition from batch to continuous-flow processing challenging. Herein, we report the use of a photochemical rotor–stator spinning disk reactor (pRS-SDR) that can handle and scale solid-containing photochemical reaction conditions in flow. Its ability to handle slurries was showcased for the TiO2-mediated aerobic photodegradation of aqueous methylene blue. The use of a fast rotating disk imposes high shear forces on the multiphase reaction mixture, ensuring its homogenization, increasing the mass transfer, and improving the irradiation profile of the reaction mixture. The pRS-SDR performance was also compared to other lab-scale reactors in terms of water treated per reactor volume and light power input.

Iron/titanium oxide-biochar (Fe2TiO5/BC): A versatile adsorbent/photocatalyst for aqueous Cr(VI), Pb2+, F- and methylene blue

This is the first report of the metal Fe-Ti oxide/biochar (Fe2TiO5/BC) composite for simultaneous removal of aqueous Pb2+, Cr6+, F- and methylene blue (MB). Primary Fe2TiO5 nano particles and aggregates were dispersed on a high surface area Douglas fir BC (∼700 m2/g) by a simple chemical co-precipitation method using FeCl3 and TiO(acac)2 salts treated by base and heated to 80 °C. This was followed by calcination at 500 °C. This method previously was used without BC to make the neat mixed oxide Fe2TiO5, exhibiting a lower energy band gap than TiO2. Adsorption of Cr(VI), Pb(II), fluoride, and MB on Fe2TiO5/BC was studied as a function of pH, equilibrium time, initial adsorbate concentration, and temperature. Adsorption isotherm studies were conducted at 5, 25, and 45 ℃ and kinetics for all four adsorbates followed the pseudo second order model. Maximum Langmuir adsorption capacities for Pb2+, Cr6+, F- and MB at their initial pH values were 141 (pH 2), 200 (pH 5), 36 (pH 6) and 229 (pH 6) mg/g at 45 ℃ and 114, 180, 26 and 210 mg/g at 25 ℃, respectively. MB was removed from the water on Fe2TiO5/BC by synergistic adsorption and photocatalytic degradation at pH 3 and 6 under UV (365 nm) light irradiation. Cr6+, Pb2+, F-, and MB each exhibited excellent removal capacities in the presence of eight different competitive ions in simulated water samples. The removal mechanisms on Fe2TiO5/BC and various competitive ion interactions were proposed. Some iron ion leaching at pH 3 catalyzed Photo-Fenton destruction of MB. Fe2TiO5, BC, and Fe2TiO5/BC bandgaps were studied to help understand photocatalysis of MB and to advance supported metal oxide photodegradation using smaller energy band gaps than the larger bandgap of TiO2 for water treatment. A long range goal is to photocatalytically destroy some sorbates with adsorbents to avoid the need for regeneration steps.

Regulation of the Volume Flow Rate of Aqueous Methyl Blue Solution and the Wettability of CuO/ZnO Nanorods to Improve the Photodegradation Performance of Related Microfluidic Reactors.

Six CuO/ZnO nanorod (CuO/ZnONR)-based microfluidic reactors were constructed for different UV irradiation durations, with which an aqueous methylene blue (MB) solution was photodegraded at varied volume flow rate Q. Via numerical and experimental routes, the effects of the Q on the kinetic adsorption rate constant Ka and the initial rate constant KA of the CuO/ZnONR-based microfluidic reactors were discussed. Moreover, a reverse contacting angle (CA) trend of CuO/ZnONRs to the reaction constant K curve of corresponding CuO/ZnONR-based microfluidic reactor suggested that the CA of CuO/ZnONRs was another key influencing factor that affected greatly the photodegradation performance of the microfluidic reactors. The Q of the aqueous MB solution and the UV irradiation duration for the photodeposition of CuO/ZnONRs were optimized to be 125 μL/min and 1.0 h, the K of the CuO/ZnONR-based microfluidic reactors reached 4.84 min-1, and the related ΔKA/K was less than 6%. Similarly, these methods and results can be employed not only to enhance the mass transport and adsorption of specific species within other nanostructured matrix material-coated microchannels but also to enlarge the actual contacting surface areas between these microchannels and the related solution, which further improve the performance of other nanostructured catalyst-based microfluidic reactors, rGO microfluidic voltage generation, and a GOx/AuNW enzymatic glucose microfluidic sensor.

Feasibility of dual-contrast fluorescence imaging of pathological breast tissues.

The combination of intravital dye, methylene blue (MB), with molecular cancer marker, pH low insertion peptide (pHLIP) conjugated with fluorescent Alexa532 (Alexa532-pHLIP), was evaluated for enhancing contrast of pathological breast tissue ex vivo. Fresh, thick breast specimens were stained sequentially with Alexa532-pHLIP and aqueous MB and imaged using dual-channel fluorescence microscopy. MB and Alexa532-pHLIP accumulated in the nuclei and cytoplasm of cancer cells, respectively. MB also stained nuclei of normal cells. Some Alexa532-pHLIP fluorescence emission was detected from connective tissue and benign cell membranes. Overall, Alexa532-pHLIP showed high affinity to cancer, while MB highlighted tissue morphology. The results indicate that MB and Alexa532-pHLIP provide complementary information and show promise for the detection of breast cancer.

Gram-scale synthesis of electrochemically oxygenated graphene nanosheets for removal of methylene blue from aqueous solution

In this study, oxygenated graphene nanosheets (OGNs) were successfully synthesized using a simple electrochemical exfoliation approach and applied to remove methylene blue (MB) in an aqueous solution. The surface morphology and structure of the OGNs were characterized by scanning electron microscopy, transmission electron microscopy, Raman, and x-ray photoelectron spectroscopy. The adsorption performance of OGNs towards aqueous MB was tested by batch experiments. Results showed that a large number of functional groups in OGNs enhanced the removal of MB from the aqueous solution due to the electrostatic interactions between the electrochemically oxygenated groups (e.g. C–OH, C–O, and C=O) and dye molecules. Using Langmuir adsorption isotherm, the maximum MB adsorption capacity (q max) was determined as high as 476.19 mg g−1. These results suggested that the as-prepared OGNs is an effective and promising adsorbent for removing MB, which could be studied extensively for color removal in wastewater treatment.

Investigation of the Dual‐Stage Method of Active Er:YLF Laser Drug Delivery Through the Nail and Laser‐Induced Transformations of the Drug Extinction Spectrum

A novel dual-stage method for active laser drug delivery (DSLADD) in the treatment of nail diseases is being presented. This method includes sequentially performed microporation of the nail with submillisecond pulses of Er:YLF laser radiation through a layer of an aqueous solution of drug deposited on the nail surface (Stage 1) and exposure this layer to the same laser radiation to deliver drug under the nail plate (Stage 2). The delivery of methylene blue (MB) as one of the possible drugs in the treatment of nail diseases is investigated. The influence of the thickness of the MB layer, as well as the energy and number of applied laser pulses, on the rate of active laser delivery is discussed. To illustrate the possible effect of delivery on the drug delivered, special attention is paid to the deformation of the extinction spectrum of MB solution after laser irradiation. Diode-pumped Er:YLF laser was used for DSLADD. The process of DSLADD under the nail plate was investigated using digital video microscopy. For different values of the thickness of MB solution layer applied to the nail plate and the energy of laser pulses, the number of laser pulses required to create a single through a microchannel in the nail plate and the number of laser pulses required to deliver the solution to the ventral side of the nail plate after its microporation were registered. The mass and the dose of MB solution penetrated under the nail plate, and the rate of MB solution delivery through a single microchannel was determined. Investigation of the influence of Er:YLF laser radiation parameters on the extinction spectrum of the drug was performed using a fiber spectrometer. The extinction spectra of the 0.001% aqueous solution of MB were recorded before and after exposure to a different number of Er:YLF laser pulses with the energy of 1-4 mJ. It was found that the minimum number of laser pulses required for active Er:YLF laser drug delivery under the nail corresponds to the MB layer thickness of 100 μm and the laser pulse energy of 4 mJ. It is shown that in this case, the rate of active laser delivery of MB solution reaches 0.26 ± 0.03 mg/pulse. The radiation of the Er:YLF laser affects the shape of the extinction spectrum of the aqueous solution of MВ, which is associated with the transition of the dye from the monomeric to dimeric state. Depending on the laser pulse energy, the fraction of a certain conformational state in the aqueous MB solution can decrease or increase, stimulating a possible change in its photodynamic and antiseptic activity. For the first time, a novel DSLADD through the nail has been described and investigated in vitro. It was demonstrated that at Er:YLF laser pulse repetition rate of f = 30 Hz, microporation of the nail plate and drug delivery through a single microchannel will be about 1.5 s. Lasers Surg. Med. © 2021 Wiley Periodicals LLC.

Adsorption and photocatalytic degradation of aqueous methylene blue using nanoporous carbon nitride

Nanoporous graphitic carbon nitride (npg-C3N4) with high performance was synthesized as visible light harvesting photocatalyst. Calcium carbonate (CaCO3) nanoparticles were synthesized and used as a templating agent along with melamine, as the precursor, for the synthesis of npg-C3N4. High porous npg-C3N4, having a specific surface area of 137.4 m2 g−1, was resulted with enhanced ability in visible light harvesting. At the mass ratio of melamine/CaCO3 = 5/4, its photocatalytic performance was 42 times higher than that of the bulk g-C3N4 when methylene blue (MB) was used as adsorbate and probe. Adsorption and kinetic isotherm showed that the adsorption process can be well described by pseudo-second-order kinetic model, with an adsorption capacity of 400.0 mg MB per gram adsorbent determined by Langmuir isotherm.