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Surfaces, Volume 6, Issue 2 (June 2023) – 6 articles

Cover Story (view full-size image): Biochar, obtained via thermochemical conversion of biomass, offers high porosity and, importantly, various surface functional groups that can be reacted with numerous compounds, e.g. organics, inorganics, and polymers. The cover schematically illustrates numerous procedures to chemically modify the surface of biochar using coupling agents, surfactants, nitrogen-containing molecules, and polymers, as well as nanocatalysts generated in situ during the thermochemical process or immobilized via post-treatment. Surface modification imparts new functionalities to biochar for high-performance applications in agriculture, water treatment, catalysis, CO₂ capture, and EMI shielding, to name but a few potential applications. View this paper

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13 pages, 3326 KiB

Open AccessArticle

Thin Luminous Tracks of Particles Released from Electrodes with A Small Radius of Curvature in Pulsed Nanosecond Discharges in Air and Argon

by Victor F. Tarasenko, Dmitry V. Beloplotov, Alexei N. Panchenko and Dmitry A. Sorokin

Surfaces 2023, 6(2), 214-226; https://doi.org/10.3390/surfaces6020014 - 14 Jun 2023

Cited by 2 | Viewed by 1168

Abstract

Features of the nanosecond discharge development in a non-uniform electric field are studied experimentally. High spatial resolution imaging showed that thin luminous tracks of great length with a cross-section of a few microns are observed against the background of discharge glow in air and argon. It has been established that the detected tracks are adjacent to brightly luminous white spots on the electrodes or in the vicinity of these spots, and are associated with the flight of small particles. It is shown that the tracks have various shapes and change from pulse to pulse. The particle tracks may look like curvy or straight lines. In some photos, they can change their direction of movement to the opposite. It was found that the particle’s track abruptly breaks and a bright flash is visible at the break point. The color of the tracks differs from that of the spark leaders, while the bands of the second positive nitrogen system dominate in the plasma emission spectra during the existence of a diffuse discharge. Areas of blue light are visible near the electrodes as well. The development of glow and thin luminous tracks in the gap during its breakdown is revealed using an ICCD camera. Physical reasons for the observed phenomena are discussed. Full article

(This article belongs to the Collection Featured Articles for Surfaces)

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35 pages, 13576 KiB

Open AccessReview

Surface Treatment of Biochar—Methods, Surface Analysis and Potential Applications: A Comprehensive Review

by Marlena Gęca, Ahmed M. Khalil, Mengqi Tang, Arvind K. Bhakta, Youssef Snoussi, Piotr Nowicki, Małgorzata Wiśniewska and Mohamed M. Chehimi

Surfaces 2023, 6(2), 179-213; https://doi.org/10.3390/surfaces6020013 - 02 Jun 2023

Cited by 6 | Viewed by 2996

Abstract

In recent years, biochar has emerged as a remarkable biosourced material for addressing global environmental, agricultural, biomedical, and energy challenges. However, the performances of biochar rest in part on finely tuning its surface chemical properties, intended to obtain specific functionalities. In this review, we tackle the surface treatment of biochar with silane and other coupling agents such as diazonium salts, titanates, ionic/non-ionic surfactants, as well as nitrogen-containing (macro)molecules. We summarize the recent progress achieved mostly in the last five years and correlate the nature and extent of functionalization to eye-catchy end applications of the surface-engineered biochar. Full article

(This article belongs to the Collection Featured Articles for Surfaces)

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15 pages, 6223 KiB

Open AccessArticle

Fabrication of Electroplated Nickel Composite Films Using Cellulose Nanofibers Introduced with Carboxy Groups as Co-Deposited Materials

by Makoto Iioka, Wataru Kawanabe, Tatsuya Kobayashi, Ikuo Shohji and Kota Sakamoto

Surfaces 2023, 6(2), 164-178; https://doi.org/10.3390/surfaces6020012 - 19 May 2023

Cited by 3 | Viewed by 1509

Abstract

In this study, the fabrication of nickel (Ni)-cellulose nanofiber (CNF) composite electroplating films was attempted using sodium carboxymethyl cellulose (CMC) and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized CNF as CNF introduced with carboxy groups. As a result, co-deposition was confirmed for both CNFs, and the former showed 82% improvement in surface Vickers hardness compared to the plated film deposited from a conventional Watts bath without CNF. Although the latter showed slightly inferior 71% improvement, the surface roughness measurement showed a smoother surface than that of the plated copper material C1100. On the other hand, the film with CMC had a rough surface. The image analysis showed that the distance between co-deposited CNF on the surface of the plated film was 40% shorter on the specimen with TEMPO CNF than CMC, indicating that a fine dispersion was obtained. In addition, a co-deposition model was proposed in which Ni is deposited from the chelate complex formed between the carboxylate of CNF and Ni ions. CNF is fixed to the plated film surface by Ni deposition and the simultaneous bond of hydrogen ions to the carboxylate, resulting in a return to the carboxy group. Full article

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19 pages, 9386 KiB

Open AccessArticle

Long-Range ACEO Phenomena in Microfluidic Channel

by Diganta Dutta, Keifer Smith and Xavier Palmer

Surfaces 2023, 6(2), 145-163; https://doi.org/10.3390/surfaces6020011 - 20 Apr 2023

Viewed by 1359

Abstract

Microfluidic devices are increasingly utilized in numerous industries, including that of medicine, for their abilities to pump and mix fluid at a microscale. Within these devices, microchannels paired with microelectrodes enable the mixing and transportation of ionized fluid. The ionization process charges the microchannel and manipulates the fluid with an electric field. Although complex in operation at the microscale, microchannels within microfluidic devices are easy to produce and economical. This paper uses simulations to convey helpful insights into the analysis of electrokinetic microfluidic device phenomena. The simulations in this paper use the Navier–Stokes and Poisson Nernst–Planck equations solved using COMSOL to determine the maximum attainable fluid velocity with an electric potential applied to the microchannel and the most suitable frequency or voltage to use for transporting the fluid. Alternating current electroosmosis (ACEO) directs and provides velocity to the ionized fluid. ACEO can also mix the fluid at low frequencies for the purpose of dispersing particles. DC electroosmosis (DCEO) applies voltage along the microchannel to create an electric field that ionizes fluid within the microchannel, making it a cost-effective method for transporting fluid. This paper explores a method for an alternate efficient utilization of microfluidic devices for efficient mixing and transportation of ionized fluid and analyzes the electrokinetic phenomena through simulations using the Navier–Stokes and Poisson Nernst–Planck equations. The results provide insights into the parameters at play for transporting the fluid using alternating current electroosmosis (ACEO) and DC electroosmosis (DCEO). Full article

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12 pages, 3127 KiB

Open AccessArticle

Charged Hybrid Microstructures in Transparent Thin-Film ITO Traps: Localization and Optical Control

by Dmitrii Shcherbinin, Vadim Rybin, Semyon Rudyi, Aliaksei Dubavik, Sergei Cherevkov, Yuri Rozhdestvensky and Andrei Ivanov

Surfaces 2023, 6(2), 133-144; https://doi.org/10.3390/surfaces6020010 - 19 Apr 2023

Cited by 2 | Viewed by 1527

Abstract

In the present study, we propose a new transparent thin-film ITO surface radio-frequency (RF) trap. Charged hybrid microstructures were localized in the developed ITO trap. We show, analytically and experimentally, that the position of the localization zones in the trapped hybrid structure are stable. The transfer of charged particles between localization zones was studied under the action of gravity-compensating laser radiation. We highlight the advantages of transparent thin-film ITO traps to investigate and manipulate charged particles. Full article

(This article belongs to the Collection Featured Articles for Surfaces)

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19 pages, 10746 KiB

Open AccessArticle

Electrostatic Assembly of Anti-Listeria Bacteriophages on a Self-Assembled Monolayer of Aminoundecanethiol: Film Morphology, Charge Transfer Studies, and Infectivity Assays

by Paula M. V. Fernandes, Cláudia Maciel, Paula Teixeira, Carlos M. Pereira and José M. Campiña

Surfaces 2023, 6(2), 114-132; https://doi.org/10.3390/surfaces6020009 - 07 Apr 2023

Viewed by 1596

Abstract

The integration of bacteriophages, a particular class of viruses that specifically infect bacteria and archaea, in biosensors for the monitoring of pathogens in foods and beverages is highly desirable. To this end, an increasing focus has been set on the exploration of covalent and physical methods for the immobilization of phages on solid surfaces. This work investigates the electrostatic assembly of tailed phages, specifically anti-Listeria monocytogenes P100 phages, on an ultrathin self-assembled monolayer (SAM) of 11-amino-1-undecanethiol (AUT). The cationic properties of AUT may allow for the electrostatic capture of P100 in a capsid-down fashion, thereby exposing the specific receptor-binding proteins on their tails to the corresponding pathogens in the analytical samples. The morphology and charge transfer behavior of the assembled films were studied with atomic force microscopy, scanning electron microscopy and electrochemical techniques. These methods provided valuable insights into the orientation of the phages and the relevant role of the pH. Biological plaque assays revealed that the immobilized phages remain active towards the target bacterium. Overall, this research portrays SAMs of amino-akylthiols as a valid platform for the oriented immobilization of bacteriophages on surfaces for electroanalytical purposes. Full article

(This article belongs to the Special Issue Biointerfaces and Interfacial Phenomena in Biology and Nanomedicine)

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