Chetan Prakash Sharma

Carbon-based nanomaterials are potentially antimicrobial in water treatment, healthcare, and environmental applications. The antibacterial properties of various carbon nanomaterial surfaces have been investigated; however, studies including direct comparisons between carbon nanomaterials with different morphology, chemistry, and wettability are few. Moreover, photoenhanced surface antibacterial activity is not fully understood. Here, we show that simple light-emitting diodes (LEDs) can enhance the antibacterial surface activity of three carbon nanomaterials with diverse surface morphologies, including laser-induced graphene (LIG), vertically aligned carbon nanotubes (VACNT), and carbon nanofibers (CNF). After 40 min of exposure to low-energy LED light, VACNTs showed the highest bacterial killing activity (93.4%), followed by CNFs (72.5%) and then LIG surfaces (69.0%). Moreover, when hydrophilicity was increased using atmospheric plasma treatment, the LED-activated antibacterial activity of all surfaces was further enhanced, with only 20 min of LED exposure resulted in 99.1%, 92.6%, and 46.1% bacterial killing efficacies for CNF, VACNT, and LIG surfaces, respectively. The LED treatment was the predominant activator of cell toxicity, resulting in reactive oxygen species and bacterial membrane permeability, although morphological factors were also seen, including an increased antibacterial efficacy of VACNT surfaces as the length of the CNTs increased and differences between the various carbon surfaces. These findings provide valuable insights into the roles of various parameters in carbon nanomaterial surfaces in antimicrobial applications.

Membrane fouling remains a major challenge in water treatment, biomedical, and pharmaceutical fields, yet understanding its mechanisms at the membrane interface remains difficult. Herein, we report a 3D impedimetric microfluidic membrane-mimic (IM3) cassette that integrates a porous membrane between microfluidic channels for real-time fouling investigation via electrochemical impedance spectroscopy (EIS). System validation using fluorescein and KCl electrolytes demonstrated reproducible charge-transfer resistance (R_ct) values and confirmed cassette robustness. Colloidal fouling studies using 800 nm polystyrene latex (PS) beads demonstrated a clear concentration-dependent behavior. High particle loading (10⁵ particles/mL) caused rapid, severe impedance increases, indicating extensive pore blockage and cake layer formation. Low loading (10¹ particles/mL) showed minimal changes, suggesting negligible fouling, as confirmed by scanning electron microscopy. The distribution of relaxation times (DRT) analysis revealed a single dominant relaxation peak at 10^-2 s that grew stronger as fouling severity increased, confirming that pore blockage raised interfacial resistance through a unified charge-transfer mechanism rather than caused diffusion-limited processes. A quantitative fouling model using EIS-measured R_ct changes captured temporal and concentration dependencies through an exponential growth framework. Maximum fouling extent (F_max) increased significantly with particle concentration (30% at 10¹ to 215% at 10⁵ particles/mL), demonstrating concentration-dependent pore blockage. The fouling rate constant (k) showed weak concentration dependence and plateaued at high loadings, indicating the limitation by available deposition sites rather than particle transport. These findings show that for PS beads, fouling is mainly governed by the extent of surface deposition (driven by concentration) rather than by the particle arrival rate (controlled by kinetics). The developed modular IM3 cassette enables customization of different membranes, channel geometries, and flow configurations. These results establish a quantitative framework linking EIS data to physically meaningful fouling phenomena, offering a versatile platform for the mechanistic investigation of dynamic membrane fouling behavior under varying particulate conditions.

Measuring consistent impedimetric signals under flow remains a persistent challenge in microfluidic electrochemical impedance spectroscopy (EIS) due to dynamic signal drift. This becomes even more challenging in the presence of redox probes or complicated electrode geometry. Such drift complicates data analysis and undermines the reliability of the impedance sensor. As its underlying origins are insufficiently understood, drift corrections are not implemented, leading to false positives and false negatives. In this work, we investigate the sources of this drift in the EIS signal of a porous, flow-through microfluidic sensor with three-dimensional electrodes. For empty channels under flow conditions, unexpected drift was observed only in the presence of a redox probe, highlighting the central role of redox-mediated interfacial processes. Surprisingly, even in the absence of a redox probe, packed channels still exhibited significant electrochemical drift. Comparing EIS signals from packed and empty channels with and without the redox couple, we can decouple the contributions of flow, porous packing, and faradaic reactions on the origins of the drift. We hypothesize that the drift arises from the combined effects of convection, interfacial double-layer formation within the porous packing, and redox probe–electrode interactions. A new root-mean-square error (RMSE)–based analysis framework is introduced to quantify drift and determine stable measurement windows, independent of sensor geometry or equivalent circuits. This algorithm is validated using single-stranded DNA detection that clearly illustrates that drift correction in EIS data significantly improves measurement reliability, and ultimately sensor selectivity, leading to fewer false positives or false negatives.

Carbon capture, utilization, and sequestration technologies are critical for limiting global temperature rise. CO₂ capture and utilization are traditionally performed as separate unit operations. Integrating them requires the use of dual‐functional materials and offers a promising pathway to overcome energy demand and cost limitations. Herein, the fabrication of an electrocatalytic membrane (eCatMem) by laser‐induced graphene processing of a gas‐separating membrane is demonstrated, enabling CO₂ reduction to formate. The membrane exhibits CO₂/N₂ permselectivity of ≈20, ensuring comparable performance when operating with pure CO₂ or a 10% CO₂/N₂ gas mixture. The eCatMem achieves current densities of 10–50 mA cm⁻² with a Faradaic efficiency of ≈70% for formate production. This is the first of its kind demonstration of integrated membrane electrochemical reactive separation to form a liquid capture media that is also a product. This approach utilizes simple, low‐cost materials and processes and offers a scalable way to integrate CO₂ capture and utilization.

Crystalline and porous metal–organic frameworks (MOFs) are potential candidates for different antibacterial, photocatalytic, and adsorption applications. Moreover, multiprincipal element nanoparticles are effective against multidrug‐resistant bacteria, and combining metals with carbon nanomaterials can enhance activity. Herein, a Tri‐MOF comprised of iron, zinc, cobalt and 2‐methyl imidazole is grown together with laser‐induced graphene (LIG) powder. Electron microscopy imaging shows the successful preparation and the crystalline nature of the LIG/Tri‐MOF composite. Fourier‐transform infrared and X‐Ray photoelectron spectroscopy confirm a noncovalent mixture of LIG and Tri‐MOF. Compared with the negligible activity of LIG alone, low doses (0.91–4.54 mg mL⁻¹) of the prepared LIG/Tri‐MOF composite show excellent antibacterial activity (≥95% bacterial removal) and a MIC of 0.6 mg mL⁻¹ for Gram‐negative bacteria, via the gradual leaching of metal ions and organic linker from the material enhanced by bacterial aggregation near the LIG/Tri‐MOF. Compared to a mixture of separately synthesized Tri‐MOF and LIG, the LIG/Tri‐MOF composite shows improved antibacterial effects. All materials show cytotoxicity for L929 mouse cell lines, the solids showing a disrupting effect on cells grown in vitro. Performance‐enhancing combinations of various materials leading to synergistic or additive antimicrobial effects are essential strategies for minimizing the possible emergence of antibiotic‐resistant strains.

Membrane technology is at the forefront of addressing critical challenges in water scarcity and environmental conservation through advanced wastewater treatment. This paper reviews membrane fouling mitigation strategies in wastewater treatment, highlighting recent advances and future directions. The review underscores the significance of membrane-based processes due to their high efficiency, adaptability, and sustainability. It discusses various membrane classifications, operational modes, and configurations, particularly focusing on cutting-edge developments in membrane-based technologies in wastewater treatment. Membrane fouling, characterized by the undesirable accumulation of particles, microorganisms, and organic compounds on membrane surfaces, impedes membrane performance, leading to permeability loss and increased energy demand. To counteract this, fouling mitigation strategies such as utilizing anti-fouling membrane materials have been at the forefront of research. These strategies aim to maintain membrane efficacy and longevity, thereby ensuring the sustainability of membrane-based wastewater treatment systems. Future research anticipates a paradigm shift towards smart membrane systems, utilizing external potentials and advanced material properties to address fouling and optimize performance, representing the next frontier in sustainable wastewater management.

Laser-induced graphene (LIG) and its composites have been explored widely in many applications. Optimization of the LIG material usually requires variation of different lasing and environmental parameters, which can lead to diverse morphological and physicochemical properties. Heteroatom doping and metal-doped LIG have been investigated, although more understanding of the fabrication parameters is needed for obtaining controlled metal nanoparticle-graphene composites. Specifically, the tuning of nanoparticles within LIG is important because nanoparticle size and distribution can lead to different physicochemical, and electrochemical properties, and thus can affect the function of the material. Here we show a systematic comparison of three different preparation processes for silver doped LIG and the variable morphologies, size of nanoparticles, physicochemical, antibacterial, and electrochemical properties. Silver nitrate was coated on a poly(ether sulfone) (PES) substrate or an LIG substrate and lased, which was compared to a lased silver/chitosan colloidal solution on PES. Surface agglomerated, or homogeneous distributions or nanoparticles with average sizes ranging from ∼13–19 nm were observed. Raman analysis indicated that the graphene quality of the samples was similar to the LIG, except for direct lasing of AgNO₃ on PES, which did not show a 2D peak at ∼2700 cm⁻¹. However, each approach resulted in composites with antibacterial activity, although different electrochemical properties, such as electron transfer resistance (R_et) and double layer capacitance (C_dl) were observed. The lased silver/chitosan material showed minimum R_et of 20.3 Ω, with highest C_dl values of 71.6 μF. Our study highlights that the variation of fabrication methodology can highly impact metal nanoparticle size, distribution, and electrochemical properties throughout the LIG composite, which might be useful to design a suitable LIG material for various applications including electrocatalysis, electrochemical sensing, and many more.