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1.
ACS Pharmacol Transl Sci ; 7(6): 1795-1806, 2024 Jun 14.
Article in English | MEDLINE | ID: mdl-38898940

ABSTRACT

Host defense peptides (HDPs), also named antimicrobial peptides (AMPs), are increasingly being recognized for serving multiple functions in protecting the host from infection and disease. Previous studies have shown that various HDPs can also neutralize lipopolysaccharide (LPS, endotoxin), as well as lipoteichoic acid (LTA), inducing macrophage activation. However, antimicrobial activity is usually accompanied by systemic toxicity which makes it difficult to use HDPs as antiendotoxin agents. Here we report that key parameters can uncouple these two functions yielding nontoxic peptides with potent LPS and LTA neutralization activities in vitro and in animal models. The data reveal that peptide length, the number, and the placement of positive charges are important parameters involved in LPS neutralization. Crucially, the peptide exhibited a separation between its membrane-disrupting and antimicrobial properties, effectively decoupling them from its ability to neutralize LPS. This essential distinction prevented systemic toxicity and led to the peptide's complete rescue of mice suffering from severe septic shock in two distinct models. Strong binding to LPS, changes in structure, and oligomerization state upon LPS binding were important factors that determined the activity of the peptides. In the face of the increasing threat of septic shock worldwide, it is crucial to grasp how we can neutralize harmful substances like LPS. This knowledge is vital for creating nontoxic treatments for sepsis.

2.
Heliyon ; 10(9): e30263, 2024 May 15.
Article in English | MEDLINE | ID: mdl-38726148

ABSTRACT

Advanced graphene-based materials have been proficiently incorporated into next-generation solar cells and supercapacitors because of their high electrical conductivity, large surface area, excellent charge-transport ability, and exceptional optical properties. Herein, we report the synthesis of graphene nanosheets (GNs) from waste cardboard via pyrolysis, with ethyl alcohol as the growth initiator. Additionally, we demonstrated the use of GNs in energy conversion and storage applications. Using the GN electrode in perovskite solar cells resulted in an excellent power conversion efficiency of ∼10.41 % for an active area of 1 cm2, indicating an enhancement of approximately 27 % compared to conventional electrodes. Furthermore, the GNs were used as active electrode materials in supercapacitors with excellent electrochemical performance and a high gravimetric specific capacitance of 167.5 F/g at a scan rate of 2 mV/s. The developed GNs can be efficiently used for energy storage, conversion, and electrochemical sensing applications.

3.
Nano Lett ; 24(10): 3133-3141, 2024 Mar 13.
Article in English | MEDLINE | ID: mdl-38477056

ABSTRACT

Liquid manipulation is essential for daily life and modern industry, and it is widely used in various fields, including seawater desalination, microfluidic robots, and biomedical engineering. Nevertheless, the current research focuses on the manipulation of individual droplets. There are a few projects for water film management. Here, we proposed a facile method of wind-triggered water film self-sculpturing based on a heterogeneous wettability surface, which is achieved by the femtosecond laser direct writing technology and femtosecond laser deposition. Under the conditions of various airflow velocities and water film thicknesses, three distinct behaviors of the water film were analyzed. As a result, when the water film thickness is lower than 4.9 mm, the self-sculpture process will occur until the whole superhydrophobic surface dewetting. Four potential applications are demonstrated, including encryption, oil containers, reconfigurable patterning, and self-splitting devices. This work provides a new approach for manipulating a water film of fluid control engineering.

4.
Nanoscale ; 15(38): 15708-15716, 2023 Oct 05.
Article in English | MEDLINE | ID: mdl-37728408

ABSTRACT

Flexible multifunctional composite films in which opposing surfaces have two or more distinct physical properties are highly applicable for wearable electronic devices, electrical power systems and biomedical engineering. However, fabrication of such "Janus" films can be time consuming, complex or economically not feasible. In this work, Janus polyimide (PI) films were prepared by femtosecond laser direct writing technology, which generated a honeycomb porous structure (HPS) on one side and a lawn-like structure (LLS) on the other. Deposition of silver nanowires (AGNWs) by drop coating on the LLS side (AGNWs@LLS) resulted in a film in which each face possessed highly distinct triple properties. The HPS side was superhydrophobic with a water contact angle (WCA) of ∼153.3° and electrically non-conductive, while the AGNWs@LLS side was superhydrophilic (WCA ∼7.8°) and highly conductive (∼3.8 Ω). Moreover, the AGNWs@LLS face showed ultra-low thermal radiation performance, almost reaching saturation. On a heating table at ∼100 °C, the temperature of the AGNWs@LLS side remained at ∼44.5 °C, while the HPS side exhibited a temperature of ∼93.9 °C. This "triple Janus film" and lasing techniques developed might be useful for designing new materials for the integration and miniaturization of multifunctional electronic equipment.

5.
Nanoscale ; 15(26): 11247-11254, 2023 Jul 06.
Article in English | MEDLINE | ID: mdl-37345814

ABSTRACT

Superwettable patterned composite surfaces are being recognized as essential components in the field of precise droplet manipulation. However, developing simple and effective methods for manufacturing such surfaces remains a challenge especially for multi-detection surfaces. Here we present a femtosecond laser-based method to create a superhydrophobic/superhydrophilic (SHB/SHL) self-splitting pattern on a polyimide film to achieve droplet multi-detection. The mechanism behind droplet self-splitting on the SHB/SHL pattern surface is related to the dynamic behaviors of liquid recoiling and spreading. This behavior was affected by two main factors, including the width of the SHB stripe, and the radius of the SHL pattern. When the characteristic width is larger than 0.2, droplets are able to fully self-split. Furthermore, the SHB/SHL pattern can be utilized for alcohol detection and multiple biological tests performed using a single drop of biological fluid. This work provides a facile strategy for precise separation and distribution of microdroplets, and potentially could be applied in fluid recognition, biological screening, and combinatorial analysis.

6.
Nano Lett ; 23(11): 4947-4955, 2023 Jun 14.
Article in English | MEDLINE | ID: mdl-37255233

ABSTRACT

Droplet steering has important applications in biomedical detection, local chemical reactions, liquid collection, and microfluidic control. Presently, droplet steering methods typically require specific paths and can be challenging to operate, involving complex fabrications for the operating systems. Here, we show a magnetically actuated superhydrophilic robot sphere (MSR) based on femtosecond laser direct writing technology for droplet steering. Through femtosecond laser treatment, uniform micro-/nanostructures are constructed on the surface of a MSR. Additionally, the contactless magnetic actuator makes it possible to remotely steer the MSR to transport droplets. After preliminary exploration of the mechanism by which MSR drives the droplet movement, the ability of MSR to control the droplet movement was systematically tested and analyzed. Moreover, the applications of the MSR in complex path liquid collection and transport, three-dimensional space transport, self-cleaning, etc., are further verified. This strategy provides a novel and reliable path for droplet manipulation and broadens its application.

7.
Nanomaterials (Basel) ; 13(5)2023 Mar 05.
Article in English | MEDLINE | ID: mdl-36903825

ABSTRACT

Numerous treatment methods such as biological digestion, chemical oxidation, and coagulation have been used to treat organic micropollutants. However, such wastewater treatment methods can be either inefficient, expensive, or environmentally unsound. Here, we embedded TiO2 nanoparticles in laser-induced graphene (LIG) and obtained a highly efficient photocatalyst composite with pollutant adsorption properties. TiO2 was added to LIG and lased to form a mixture of rutile and anatase TiO2 with a decreased band gap (2.90 ± 0.06 eV). The LIG/TiO2 composite adsorption and photodegradation properties were tested in solutions of a model pollutant, methyl orange (MO), and compared to the individual and mixed components. The adsorption capacity of the LIG/TiO2 composite was 92 mg/g using 80 mg/L MO, and together the adsorption and photocatalytic degradation resulted in 92.8% MO removal in 10 min. Adsorption enhanced photodegradation, and a synergy factor of 2.57 was seen. Understanding how LIG can modify metal oxide catalysts and how adsorption can enhance photocatalysis might lead to more effective pollutant removal and offer alternative treatment methods for polluted water.

8.
ACS Appl Bio Mater ; 6(2): 883-890, 2023 02 20.
Article in English | MEDLINE | ID: mdl-36692432

ABSTRACT

Laser-induced graphene (LIG) is a method of generating a foam-like conformal carbon layer of porous graphene on many types of carbon-based surfaces. This electrically conductive material has been shown to be useful in many applications including environmental technology and includes low fouling and antimicrobial surfaces and can address persistent environmental challenges spawned by bacterial and viral contaminates. Here, we show that a single film of LIG stores charge when an electrical current is applied and dissipates charge when the current is stopped, which results in electricidal surface antibacterial potency. The amount of accumulated and dissipated charge on a single strip of LIG was quantified with an electrometer by generating LIG on both sides of a nonconducting polyimide film, which showed up to 65 pC of charge when the distance between the surfaces was 94 µm corresponding to an areal capacitance of 1.63 pF/cm2. We further corroborate the stored charge decay of a single LIG strip with bacteria death via direct electrical contact. Antimicrobial rates decreased with the same monotonic pattern as the loss of charge from the LIG film (i.e., AR ∼ 97% 0 s after voltage source disconnection vs AR ∼ 21% 90 s after disconnection) showing bacterial death as a function of delayed LIG exposure time after applied voltage disconnection. In terms of energy efficiency, this translates to an increased bacteria potency of ∼170% for the equivalent energy costs as that previously estimated. Finally, we present a mechanistic explanation for the capacitive behavior and the electricidal effects for a single plate of LIG.


Subject(s)
Graphite , Graphite/pharmacology , Carbon , Anti-Bacterial Agents/pharmacology , Bacteria , Lasers
9.
Biofouling ; 38(9): 940-951, 2022 10.
Article in English | MEDLINE | ID: mdl-36511186

ABSTRACT

Biofouling on surfaces in contact with sea- or brackish water can severely impact the function of devices like reverse osmosis modules. Single species laboratory assays are frequently used to test new low fouling materials. The choice of bacterial strain is guided by the natural population present in the application of interest and decides on the predictive power of the results. In this work, the analysis of the bacterial community present in brackish water from Mashabei Sadeh, Israel was performed and Rheinheimera sp. was detected as a prominent microorganism. A Rheinheimera strain was selected to establish a short-term accumulation assay to probe initial bacterial attachment as well as biofilm growth to determine the biofilm-inhibiting properties of coatings. Both assays were applied to model coatings, and technically relevant polymers including laser-induced graphene. This strategy might be applied to other water sources to better predict the fouling propensity of new coatings.


Subject(s)
Biofouling , Polymers , Biofilms , Carbon , Surface Properties , Biofouling/prevention & control , Bacteria , Saline Waters
10.
ACS Appl Mater Interfaces ; 14(46): 52448-52458, 2022 Nov 23.
Article in English | MEDLINE | ID: mdl-36349685

ABSTRACT

Laser-induced graphene (LIG) has recently become a point of attraction globally as an environmentally friendly method to fabricate graphene foam in a single step using a CO2 laser. The electrical properties of LIG are studied in different environmental applications, such as bacterial inactivation, antibiofouling, and pollutant sensing. Furthermore, metal or nonmetal doping of graphene enhances its catalytical performance in pollutant degradation and decontamination. Magnéli phase (TinO2n-1) is a substoichiometric titanium oxide known for its high electrocatalytic behavior and chemical inertness and is being explored as a membrane or electrode material for environmental decontamination. Here, we show the fabrication and characterization of LIG-Magnéli-phase (Ti4O7) titanium suboxide composites as electrodes and filters on poly(ether sulfone). Unlike undoped LIG electrodes, the doped Ti4O7-LIG electrodes exhibit enhanced electrochemical activity, as demonstrated in electrochemical characterization using cyclic voltammetry and electrochemical impedance spectroscopy. Due to the in situ generation of hydroxyl radicals on the surface, the doped electrodes exhibit increase in methylene blue degradation and microorganism removal. Effects of voltage and doping were examined, resulting in a clear trend of degradation and decontamination performance proportional to the doping concentration and applied voltage giving the best result at 2.5 V for 10% Ti4O7 doping. The LIG-Ti4O7 surfaces also showed biofilm inhibition against mixed bacterial culture. The flow-through filtration using a LIG-Ti4O7 conductive filter showed complete bacterial killing with 6 log removal in the permeate at 2.5 V, an enhancement of ∼2.5 log compared to undoped LIG filters at a flow rate of ∼500 L m-2 h-1. The facile fabrication of Ti4O7-doped LIG with enhanced electrochemical properties can be effectively used for energy and environmental applications.


Subject(s)
Environmental Pollutants , Graphite , Water Pollutants, Chemical , Graphite/chemistry , Titanium/chemistry , Water Pollutants, Chemical/chemistry , Oxidation-Reduction , Lasers
11.
ACS Appl Mater Interfaces ; 14(39): 44713-44723, 2022 Oct 05.
Article in English | MEDLINE | ID: mdl-36083630

ABSTRACT

Early and reliable detection of an infectious viral disease is critical to accurately monitor outbreaks and to provide individuals and health care professionals the opportunity to treat patients at the early stages of a disease. The accuracy of such information is essential to define appropriate actions to protect the population and to reduce the likelihood of a possible pandemic. Here, we show the fabrication of freestanding laser-induced graphene (FLIG) flakes that are highly sensitive sensors for high-fidelity viral detection. As a case study, we show the detection of SARS-CoV-2 spike proteins. FLIG flakes are nonembedded porous graphene foams ca. 30 µm thick that are generated using laser irradiation of polyimide and can be fabricated in seconds at a low cost. Larger pieces of FLIG were cut forming a cantilever, used as suspended resonators, and characterized for their electromechanics behavior. Thermomechanical analysis showed FLIG stiffness comparable to other porous materials such as boron nitride foam, and electrostatic excitation showed amplification of the vibrations at frequencies in the range of several kilo-hertz. We developed a protocol for aqueous biological sensing by characterizing the wetting dynamic response of the sensor in buffer solution and in water, and devices functionalized with COVID-19 antibodies specifically detected SARS-CoV-2 spike protein binding, while not detecting other viruses such as MS2. The FLIG sensors showed a clear mass-dependent frequency response shift of ∼1 Hz/pg, and low nanomolar concentrations could be detected. Ultimately, the sensors demonstrated an outstanding limit of detection of 2.63 pg, which is equivalent to as few as ∼5000 SARS-CoV-2 viruses. Thus, the FLIG platform technology can be utilized to develop portable and highly accurate sensors, including biological applications where the fast and reliable protein or infectious particle detection is critical.


Subject(s)
COVID-19 , Graphite , COVID-19/diagnosis , Graphite/chemistry , Humans , Lasers , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/analysis , Water
12.
ACS Appl Mater Interfaces ; 13(49): 59373-59380, 2021 Dec 15.
Article in English | MEDLINE | ID: mdl-34851621

ABSTRACT

Laser-induced graphene (LIG) is uniquely positioned to advance applications in which electrically conductive carbon coatings are required. Recently, the antifouling, antiviral, and antibacterial properties of LIG have been proven in both air and water filtration applications. For example, an unsupported LIG based filter (pore size: ∼0.3 µm) demonstrated exceptional air filtration properties, while its joule heating effects successfully sterilized and removed unwanted biological components in air despite persisting challenges such as pressure drop, energy consumption, and lack of mechanical robustness. Here, we developed a polyimide (PI) non-woven supported LIG air filter with negligible pressure drop changes compared to the non-woven support material and showed that low electrical current density inactivates aerosolized bacteria. A current density of 4.5 mA/cm2 did not cause significant joule heating, and 97.2% bacterial removal was obtained. The low-voltage antibacterial mechanism was elucidated using bacterial inhibition experiments on a titanium surface and on an LIG surface fabricated on dense PI films. Complete sterilization was obtained using current densities of ∼8 mA/cm2 applied for 2 min or ∼ 6 mA/cm2 for 10 min upon the dense PI-LIG surface. Lastly, >98% bacterial removal was observed using a low-resistance LIG-coated non-woven polyimide air filter at 5 V. However, only very low voltages (∼0.3 V) were needed to remove ∼99% Pseudomonas aeruginosa bacteria and 100% of T4 virus when the LIG-coated filters were hybridized with a stainless steel mesh. Our results show that low current density levels at very low voltages are sufficient for substantial bacterial and viral inactivation, and that these principles might be effectively used in a wide number of air filtration applications such as air conditioners or other ventilation systems, which might limit the spread of infectious particles in hospitals, homes, workplaces, and the transportation industry.


Subject(s)
Anti-Bacterial Agents/pharmacology , Antiviral Agents/pharmacology , Bacteriophage T4/drug effects , Coated Materials, Biocompatible/pharmacology , Graphite/chemistry , Pseudomonas aeruginosa/drug effects , Air Filters , Anti-Bacterial Agents/chemistry , Antiviral Agents/chemistry , Coated Materials, Biocompatible/chemistry , Lasers , Materials Testing , Microbial Sensitivity Tests , Particle Size
13.
ACS Nano ; 15(10): 15461-15470, 2021 10 26.
Article in English | MEDLINE | ID: mdl-34633174

ABSTRACT

Graphene research has steadily increased, and its commercialization in many applications is becoming a reality because of its superior physicochemical properties and advances in synthesis techniques. However, bulk-scale production of graphene still requires large amounts of solvents, electrochemical treatment, or sonication. Recently, a method was discovered to convert bulk quantities of carbonaceous materials to graphene using flash Joule heating (FJH) and, so named, flash graphene (FG). This method can be used to turn various solid wastes containing the prerequisite element carbon into FG. Globally, more than 2 billion tons of municipal solid waste (MSW) are generated every year and, in many municipalities, are becoming unmanageable. The most commonly used waste management methods include recycling, composting, anaerobic digestion, incineration, gasification, pyrolysis, and landfill disposal. However, around 70% of global waste ends up in landfills or open dumps, while the rest is recycled, composted, or incinerated. Even the various waste valorization techniques, such as pyrolysis and gasification, produce some waste residues that have their ultimate destination in landfills. Thus, technologies that can minimize waste volume or convert waste into valuable products are required. The thermal treatment process of FJH for FG production provides both waste volume reduction and valorization in the form of FG. In this Perspective, we provide an overview of FJH and its possible applications in various types of waste conversion/valorization. We describe the typical current MSW management system as well as the potential for creating FG at various stages and propose a schematic plan for the incorporation of FG in MSW management. We also analyze the strengths, weaknesses, opportunities, and threats of MSW as an FG precursor in terms of technical, economic, environmental, and social sustainability. This valuable waste valorization and management strategy can help achieve near-zero waste and an economy-boosting MSW management system.


Subject(s)
Graphite , Refuse Disposal , Waste Management , Solid Waste/analysis , Waste Disposal Facilities
14.
Materials (Basel) ; 14(12)2021 Jun 09.
Article in English | MEDLINE | ID: mdl-34207716

ABSTRACT

Interest in the pathogenesis, detection, and prevention of viral infections has increased broadly in many fields of research over the past year. The development of water treatment technology to combat viral infection by inactivation or disinfection might play a key role in infection prevention in places where drinking water sources are biologically contaminated. Laser-induced graphene (LIG) has antimicrobial and antifouling surface effects mainly because of its electrochemical properties and texture, and LIG-based water filters have been used for the inactivation of bacteria. However, the antiviral activity of LIG-based filters has not yet been explored. Here we show that LIG filters also have antiviral effects by applying electrical potential during filtration of the model prototypic poxvirus Vaccinia lister. This antiviral activity of the LIG filters was compared with its antibacterial activity, which showed that higher voltages were required for the inactivation of viruses compared to that of bacteria. The generation of reactive oxygen species, along with surface electrical effects, played a role in the mechanism of virus inactivation. This new property of LIG highlights its potential for use in water and wastewater treatment for the electrochemical disinfection of various pathogenic microorganisms, including bacteria and viruses.

15.
J Colloid Interface Sci ; 592: 342-348, 2021 Jun 15.
Article in English | MEDLINE | ID: mdl-33677194

ABSTRACT

Facemasks are considered the most effective means for preventing infection and spread of viral particles. In particular, the coronavirus (COVID-19) pandemic underscores the urgent need for developing recyclable facemasks due to the considerable environmental damage and health risks imposed by disposable masks and respirators. We demonstrate synthesis of nanoporous membranes comprising carbon dots (C-dots) and poly(vinylidene fluoride) (PVDF), and demonstrate their potential use for recyclable, self-sterilized facemasks. Notably, the composite C-dot-PVDF films exhibit hydrophobic surface which prevents moisture accumulation and a compact nanopore network which allows both breathability as well as effective filtration of particles above 100 nm in diameter. Particularly important, self-sterilization occurs upon short solar irradiation of the membrane, as the embedded C-dots efficiently absorb visible light, concurrently giving rise to elevated temperatures through heat dissipation.


Subject(s)
COVID-19/prevention & control , Carbon/chemistry , Masks/virology , Nanopores , SARS-CoV-2 , Sterilization , Sunlight , COVID-19/transmission , Humans
16.
ACS Appl Mater Interfaces ; 13(1): 1452-1462, 2021 Jan 13.
Article in English | MEDLINE | ID: mdl-33390015

ABSTRACT

The removal of emerging environmental pollutants in water and wastewater is essential for high drinking water quality or for discharge to the environment. Electrochemical treatment is a promising technology shown to degrade undesirable organic compounds or metals via oxidation and reduction, and carbon-based electrodes have been reported. Here, we fabricated a robust, porous laser-induced graphene (LIG) electrode on a commercial water treatment membrane using the multilasing technique and demonstrated the electrochemical removal of iohexol, an iodine contrast compound, and chromium(VI), a highly toxic heavy metal ion. Multiple lasing resulted in a more ordered graphitic lattice, a more physically robust carbon layer, and a 3-4-fold higher electrical conductivity. These properties ultimately led to a more efficient electrochemical process, and the optimized LIG electrodes showed a higher hydrogen peroxide (H2O2) generation. At 3 V, 90% of Cr(VI) was removed after 6 h and reached >95% removal after 8 h at pH 2. Cr(VI) was mainly reduced to Cr(III), with small amounts of Cr(I) and Cr(0), which were partially deposited on the electrode membrane surface, confirmed with X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy analysis. Under the same conditions, 50% of iohexol was degraded after 6 h and the transformation products (TPs) were identified using ultra-performance liquid chromatography coupled with mass spectroscopy. A total of seven main intermediates were identified including deiodinated TPs (m/z = 695, 570, and 443), probably occurring via three transformation pathways including oxidative deiodination, amide hydrolysis, and deacetylation. The electrical energy costs calculated for the removal of 2 mg L-1 Cr(VI) was ∼$0.08/m3 in this system. Taken together, the porous LIG electrodes might be utilized for electrochemical removal of emerging contaminants in multiple applications because they can be rapidly formed on flexible polymer substrates at low cost.

17.
ACS Appl Bio Mater ; 4(5): 4191-4200, 2021 05 17.
Article in English | MEDLINE | ID: mdl-35006832

ABSTRACT

Membrane separation processes including reverse osmosis are now considered essential techniques for water and wastewater treatment, especially in water-scarce areas where desalination and water reuse can augment the water supply. However, biofouling remains a significant challenge for these processes and in general for marine biological fouling, which results in increased energy consumption and high operational costs. Especially in flat sheet membrane modules, intense biofilm growth occurs on the feed spacer at points of contact to the membrane surface. Here, we developed an ultrastable superhydrophobic antibiofouling feed spacer that resists biofilm growth. A commercial polypropylene feed spacer was coated with poly(dimethylsiloxane) (PDMS), and then, candle soot nanoparticles (CSNPs) were embedded into the ultrathin layer of PDMS, which resulted in a superhydrophobic nanostructured surface with a contact angle >150°. The CSNP-coated spacer was examined for inhibition of biofilm growth by a cross-flow membrane channel using Pseudomonas aeruginosa (PA01), and the coating was examined for effectiveness in marine fouling by testing the adhesion of marine bacterium Cobetia marina and diatom Navicula perminuta in a dynamic accumulation assay. In all cases, the CSNP coatings showed almost complete elimination of biofilm growth under the conditions tested. Confocal laser scanning microscopy and scanning electron microscopy indicated a 99% reduction in biofilm growth on the modified spacers compared to the uncoated controls. This effect was attributed to the superhydrophobic nanostructured surface, where trapped gasses formed a plastron on the coating. This plastron was observed to be extremely stable over time and could even be replenished at elevated temperatures. Development of similar antibiofouling coatings on feed spacers or other marine applications might lead to improvements in many industrial processes including membrane filtration where increased membrane life span and reduced energy consumption are key to implementation.


Subject(s)
Coated Materials, Biocompatible/chemistry , Dimethylpolysiloxanes/chemistry , Water Purification , Water/chemistry , Hydrophobic and Hydrophilic Interactions , Materials Testing , Nanoparticles/chemistry , Particle Size
18.
J Phys Chem Lett ; 11(4): 1397-1403, 2020 Feb 20.
Article in English | MEDLINE | ID: mdl-31997642

ABSTRACT

Ion-exchange membranes hybridized with laser-induced graphene (LIG) might lead to membranes with functional surface effects such as antifouling, antibacterial, or joule heating effects; however, understanding the change in the electrical properties of the membrane is essential. Here we studied LIG-modified ion-exchange polymeric membranes using electrochemical impedance spectroscopy (EIS). The conductivity of the anionic sulfonated poly(ether sulfone) membranes and the effective capacitance of the membrane-electrolyte interface were obtained by fitting the EIS spectra to an electrochemical equivalent circuit and compared with LIG-modified nonionic poly(ether sulfone) films. The transport selectivity (as the relative permeability) of counterions (K+, Na+, Mg2+, Ca2+) across the membrane was quantified using the membrane's conductivities obtained from the EIS measurements. The total ohmic resistance of the membrane was directly correlated to the polymer thickness (with negligible contribution from the conductive LIG layer), thereby establishing EIS as a rapid, low-cost, and noninvasive method to accurately probe substrate usage in LIG modification.

19.
Chem Commun (Camb) ; 55(48): 6890-6893, 2019 Jun 11.
Article in English | MEDLINE | ID: mdl-31134255

ABSTRACT

Previously, laser-induced graphene (LIG) coated surfaces were shown to resist biofilm growth, although the material was not strongly antibacterial. Here, we show LIG surfaces doped with silver nanoparticles (Ag0 or AgNPs) as highly antibacterial surfaces. Starting from AgNO3 polyethersulfone (PES) polymer substrates, silver nanoparticles between 5-10 nm were generated in situ during the lasing process and stably embedded in the fibrous and porous structure of LIG in a single step. These silver doped LIG (Ag@LIG) surfaces were highly toxic to bacteria via a mechanism of both Ag+ ion release and possible surface toxicity of the AgNPs. The added antibacterial function of Ag-nanoparticles expands the functionality of LIG coated surfaces and might lead to highly effective point of use/entry devices in rural areas or in disaster situations with contaminated water sources.


Subject(s)
Anti-Bacterial Agents/chemistry , Biofilms/drug effects , Coated Materials, Biocompatible/chemistry , Graphite/chemistry , Metal Nanoparticles/chemistry , Silver/chemistry , Anti-Bacterial Agents/pharmacology , Lasers , Polymers/chemistry , Pseudomonas aeruginosa/drug effects , Sulfones/chemistry , Surface Properties
20.
ACS Appl Mater Interfaces ; 11(11): 10914-10921, 2019 Mar 20.
Article in English | MEDLINE | ID: mdl-30794741

ABSTRACT

Graphene nanomaterials can feature both superb electrical conductivity and unique physical properties such as extreme surface wettability, which are potentially applicable for many purposes including water treatment. Laser-induced graphene (LIG) is an electrically conductive three-dimensional porous carbon material prepared by direct laser writing on various polymers in ambient conditions with a CO2 laser. Low-fouling LIG coatings in water technology have been reported; however, the mechanical strength and the separation properties of LIG-coated membranes are limited. Here, we show mechanically robust electrically conductive LIG-poly(vinyl alcohol) (PVA) composite membranes with tailored separation properties suitable for ultrafiltration processes. PVA has outstanding chemical and physical stability with good film-forming properties and is a biocompatible and nontoxic polymer. Compared to LIG-coated filters, the PVA-LIG composite membrane filters exhibited up to 63% increased bovine serum albumin rejection and up to ∼99.9% bacterial rejection, which corresponded well to the measured molecular weight cutoff ∼90 kDa. Compared to LIG fabricated on a polymer membrane control, the composite membranes showed similar excellent antifouling properties including low protein adsorption, and the antibiofilm effects were more pronounced at lower PVA concentrations. Notably for the antibacterial capabilities, the LIG-supporting layer maintained its electrical conductivity and a selected LIG-PVA composite used as electrodes showed complete elimination of mixed bacterial culture viability and indicated that the potent antimicrobial killing effects were maintained in the composite. This work demonstrates that the use of LIG for practical industrial filtration applications is possible.

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