Nanomanufacturing

19 pages, 3064 KB

Open AccessArticle

Time-Dependent Hydrothermal Synthesis of TiO₂ in the Presence of Zn²⁺: Effects on Photoconductivity

by Tilemachos Georgakopoulos, Georgios Samourgkanidis, Nadia Todorova, Christos Trapalis and Katerina Pomoni

Nanomanufacturing 2025, 5(4), 17; https://doi.org/10.3390/nanomanufacturing5040017 - 3 Nov 2025

Abstract

Titanium dioxide nanoparticles were synthesized via hydrothermal treatment of tetrabutyl titanate in sulfuric acid, with controlled reaction times (10 h and 24 h) and zinc sulfate as a modifier. XRD confirmed exclusive formation of the anatase phase, with longer reaction times promoting crystallite growth. SEM and BET analyses showed that introducing Zn during synthesis suppressed agglomeration, decreased the particle size, and modified porosity while maintaining the mesoporous nature of all samples. UV–Vis diffuse reflectance spectroscopy showed a band gap near 3.2 eV, which was unaffected by Zn content or morphology. Photoconductivity studies showed a several-orders-of-magnitude increase in conductivity under vacuum conditions, especially in samples heat-treated for 24 h, due to the generation of oxygen vacancies and

{Ti}^{3 +}

states that prolong the carrier lifetime. In particular, the TS24Z8 sample exhibited a photoconductivity enhancement of five orders of magnitude relative to its dark conductivity and nearly 30 times higher than that of the commercial P25 benchmark. In contrast, in air, photoconductivity remained low because of strong surface recombination with adsorbed oxygen. These results emphasize the critical influence of hydrothermal duration and zinc incorporation on the defect structure and electronic response of

{TiO}_{2}

, offering insights for improved photocatalytic and optoelectronic applications. Full article

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11 pages, 1927 KB

Open AccessArticle

Sodium-Doped Carbon Dots as Fluorescent Sensor for Highly Selective Detection of TNP Explosives in the Environment

by Tianyu Gao, Xuehua Sun and Hongmei Chai

Nanomanufacturing 2025, 5(4), 16; https://doi.org/10.3390/nanomanufacturing5040016 - 23 Oct 2025

Viewed by 186

Abstract

Given the environmental hazards of 2,4,6-trinitrophenol (TNP) and the limitations of existing detection methods, sodium-doped fluorescent carbon dots (Na-CDs) were successfully synthesized via a one-step hydrothermal method using citric acid and ascorbic acid as carbon sources. Compared with undoped carbon quantum dots, Na-CDs exhibited nearly identical surface functional groups but significantly enhanced fluorescence stability and markedly improved selective responsiveness toward TNP. Accordingly, a Na-CD-based fluorescent probe was developed for the highly selective detection of TNP. Results demonstrated a good linear relationship between the relative fluorescence intensity change (F₀ − F)/F₀ and TNP concentration ranging from 7 × 10⁻⁷ to 2 × 10⁻⁵ mol/L, with a detection limit of 3.5 × 10⁻⁸ mol/L. When applied to detect TNP in local river water samples, the method achieved recoveries of 95.40–104.0%, confirming its reliability for real-world environmental sample analysis. This study develops a novel, sensitive, and highly selective approach for monitoring TNP in environmental systems. Full article

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35 pages, 8289 KB

Open AccessArticle

Tuning Optical and Photoelectrochemical Properties of TiO₂/WO_x Heterostructures by Reactive Sputtering: Thickness-Dependent Insights

by Lucas Diniz Araujo, Bianca Sartori, Matheus Damião Machado Torres, David Alexandro Graves, Benedito Donizeti Botan-Neto, Mariane Satomi Weber Murase, Nilton Francelosi Azevedo Neto, Douglas Marcel Gonçalves Leite, Rodrigo Sávio Pessoa, Argemiro Soares da Silva Sobrinho and André Luis Jesus Pereira

Nanomanufacturing 2025, 5(4), 15; https://doi.org/10.3390/nanomanufacturing5040015 - 15 Oct 2025

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Abstract

Metal-oxide heterostructures represent an effective strategy to overcome the limitations of pristine TiO₂, including its ultraviolet-only light absorption and rapid electron–hole recombination, which hinder its performance in solar-driven applications. Among various configurations, coupling TiO₂ with tungsten oxide (WO_x) forms a favorable type-II band alignment that enhances charge separation. However, a comprehensive understanding of how WO_x overlayer thickness affects the optical and photoelectrochemical (PEC) behavior of device-grade thin films remains limited. In this study, bilayer TiO₂/WO_x heterostructures were fabricated via reactive DC magnetron sputtering, with controlled variation in WO_x thickness to systematically investigate its influence on the structural, optical, and PEC properties. Adjusting the WO_x deposition time enabled precise tuning of light absorption, interfacial charge transfer, and donor density, resulting in markedly distinct PEC responses. The heterostructure obtained with 30 min of WO_x deposition demonstrated a significant enhancement in photocurrent density under AM 1.5G illumination, along with reduced charge-transfer resistance and improved capacitive behavior, indicating efficient charge separation and enhanced charge storage at the electrode–electrolyte interface. These findings underscore the potential of sputtered TiO₂/WO_x bilayers as advanced photoanodes for solar-driven hydrogen generation and light-assisted energy storage applications. Full article

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24 pages, 4218 KB

Open AccessArticle

Friction and Wear Performance of Carbon Nanotubes Reinforced Co-Based Atmospheric Plasma-Sprayed Coatings

by Ilias Georgiopoulos, Dimitra Giasafaki, Dia Andreouli and Chara I. Sarafoglou

Nanomanufacturing 2025, 5(4), 14; https://doi.org/10.3390/nanomanufacturing5040014 - 24 Sep 2025

Viewed by 388

Abstract

Atmospheric plasma spraying was used to create composite coatings employing mixed alloy matrices supplemented with carbon-based solid lubricants as feedstock materials. The current study’s goal was to examine the tribological properties of these coatings and explore the potential benefits of using CNTs as a nano-additive to minimize wear and friction while enhancing lubrication conditions in tribosystems such as piston ring–cylinder liner systems. Pin-on-disk measurements are used to correlate the chemical composition of feedstock materials with the friction coefficient and wear rate during coating operation. The enhanced behavior of the produced coatings is investigated. The anti-wear performance of Co-based cermet and metal alloys coatings, as well as the enhanced lubrication conditions during operation, are shown. In-depth discussion is provided regarding how the features of the feedstock powder affect the quality and performance of the produced coatings. The results showed that coatings based on the CoMo alloy exhibited an increase in wear due to CNT agglomeration. In contrast, CNT addition led to an improvement in bonding strength by up to 33%, a reduction in wear rate by up to 80%, and a decrease in the coefficient of friction from approximately 0.70 to 0.35 in CoNi cermet coatings. These findings demonstrate the role of CNTs in coating performance for demanding tribological applications. Full article

(This article belongs to the Topic Innovative Synthesis and Applications of Functional Nanomaterials)

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Nanomanufacturing, Volume 5, Issue 4 (December 2025) – 4 articles

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