Composition/Structural Evolution and Optical Properties of ZnO/Zn Nanoparticles by Laser Ablation in Liquid Media

CTAB-crafted ZnO nanostructures for environmental remediation and pathogen control

This study addresses the critical need for efficient and sustainable methods to tackle organic pollutants and microbial contamination in water. The present work aim was to investigate the potential of multi-structured zinc oxide nanoparticles (ZnO NPs) for the combined photocatalytic degradation of organic pollutants and antimicrobial activity. A unique fusion of precipitation-cum-hydrothermal approaches was precisely employed to synthesize the ZnO NPs, resulting in remarkable outcomes. The synthesized CTAB/ZnO NPs demonstrated exceptional properties: they were multi-structured and crystalline with a size of 40 nm and possessed a narrow band gap energy of 2.82 eV, enhancing light absorption for photocatalysis. These nanoparticles achieved an impressive degradation efficiency of 91.75% for Reactive Blue-81 dye within 105 min under UV irradiation. Furthermore, their photocatalytic performance metrics were outstanding, including a quantum yield of 1.73 × 10-4 Φ, a kinetic reaction rate of 3.89 × 102 µmol g-1 h-1, a space-time yield of 8.64 × 10-6 molecules photon-1 mg-1, and a figure-of-merit of 1.03 × 10-9 mol L J-1 g-1 h-1. Notably, the energy consumption was low at 1.73 × 10-4 J mol-1, compared to other systems. Additionally, the ZnO NPs exhibited effective antimicrobial activity against S. aureus and P. aeruginosa. This research underscores the potential of tailored ZnO NPs as a versatile solution for addressing both organic pollution and microbial contamination in water treatment processes. The low energy consumption further enhances its attractiveness as a sustainable solution.

Fundamentals and comprehensive insights on pulsed laser synthesis of advanced materials for diverse photo- and electrocatalytic applications

The global energy crisis is increasing the demand for innovative materials with high purity and functionality for the development of clean energy production and storage. The development of novel photo- and electrocatalysts significantly depends on synthetic techniques that facilitate the production of tailored advanced nanomaterials. The emerging use of pulsed laser in liquid synthesis has attracted immense interest as an effective synthetic technology with several advantages over conventional chemical and physical synthetic routes, including the fine-tuning of size, composition, surface, and crystalline structures, and defect densities and is associated with the catalytic, electronic, thermal, optical, and mechanical properties of the produced nanomaterials. Herein, we present an overview of the fundamental understanding and importance of the pulsed laser process, namely various roles and mechanisms involved in the production of various types of nanomaterials, such as metal nanoparticles, oxides, non-oxides, and carbon-based materials. We mainly cover the advancement of photo- and electrocatalytic nanomaterials via pulsed laser-assisted technologies with detailed mechanistic insights and structural optimization along with effective catalytic performances in various energy and environmental remediation processes. Finally, the future directions and challenges of pulsed laser techniques are briefly underlined. This review can exert practical guidance for the future design and fabrication of innovative pulsed laser-induced nanomaterials with fascinating properties for advanced catalysis applications.

Photoluminescent neodymium-doped ZnO nanocrystals prepared by laser ablation in solution for NIR-II fluorescence bioimaging

The work reports on the use of laser ablation and post-ablation irradiation techniques for the preparation Nd3+ doped ZnO nanoparticles (NPs). The focus has been made on photoluminescence of Nd-doped ZnO NPs in the second near infrared (NIR-II) spectral window (1000-1700 nm) of the biological transparency. Morphology, phase composition and optical properties of the synthesized NPs were studied by absorption and photoluminescence spectroscopy, X-Ray diffraction (XRD) and transmission (TEM) electron microscopy. Near-infrared luminescence of Nd3+ doped ZnO nanocrystals in the region of 1000-1400 nm was detected both upon excitation from the ground state (800 nm) and upon UV excitation. The latter proves the incorporation of the Nd3+ into ZnO lattice as photoluminescence occurs through the transfer of excitation energy from the ZnO matrix to the Nd3+ ion. The possibility of control over the luminescence properties by a variation of solvent composition and by additional laser irradiation was demonstrated.

Novel perspectives of laser ablation in liquids: the formation of a high-pressure orthorhombic FeS phase and absorption of FeS-derived colloids on a porous surface for solar-light photocatalytic wastewater cleaning

A pulsed Nd : YAG laser ablation of FeS in water and ethanol produces FeS-derived colloidal nanoparticles that absorb onto immersed porous ceramic substrates and create solar-light photocatalytic surfaces. The stability, size distribution and zeta potential of the nanoparticles were assessed by dynamic light scattering. Raman, UV-Vis and XP spectroscopy and electron microscopy reveal that the sol nanoparticles have their outmost layer composed of ferrous and ferric sulphates and those produced in water are made of high-pressure orthorhombic FeS, cubic magnetite Fe3O4 and tetragonal maghemite γ-Fe2O3, while those formed in ethanol contain hexagonal FeS and cubic magnetite Fe3O4. Both colloids absorb solar light and their adsorption to porous ceramic surfaces creates functionalized ceramic surfaces that induce methylene blue degradation by daylight. The laser induced process thus offers an easy and efficient way for the functionalization of porous surfaces by photocatalytic nanoparticles that avoids aggregation in the liquid phase. The formation of an orthorhombic high-pressure FeS phase stable under ambient conditions is the first example of high-pressure structures produced by laser ablation in liquid without the assistance of an electric field.

Room-Temperature Laser Synthesis in Liquid of Oxide, Metal-Oxide Core-Shells, and Doped Oxide Nanoparticles

Although oxide nanoparticles are ubiquitous in science and technology, a multitude of compositions, phases, structures, and doping levels exist, each one requiring a variety of conditions for their synthesis and modification. Besides, experimental procedures are frequently dominated by high temperatures or pressures and by chemical contaminants or waste. In recent years, laser synthesis of colloids emerged as a versatile approach to access a library of clean oxide nanoparticles relying on only four main strategies running at room temperature and ambient pressure: laser ablation in liquid, laser fragmentation in liquid, laser melting in liquid and laser defect-engineering in liquid. Here, established laser-based methodologies are reviewed through the presentation of a panorama of oxide nanoparticles which include pure oxidic phases, as well as unconventional structures like defective or doped oxides, non-equilibrium compounds, metal-oxide core-shells and other anisotropic morphologies. So far, these materials showed several useful properties that are discussed with special emphasis on catalytic, biomedical and optical application. Yet, given the endless number of mixed compounds accessible by the laser-assisted methodologies, there is still a lot of room to expand the library of nano-crystals and to refine the control over products as well as to improve the understanding of the whole process of nanoparticle formation. To that end, this review aims to identify the perspectives and unique opportunities of laser-based synthesis and processing of colloids for future studies of oxide nanomaterial-oriented sciences.

Synthesis, Characterization, and Three-Dimensional Structure Generation of Zinc Oxide-Based Nanomedicine for Biomedical Applications

Zinc oxide (ZnO) nanoparticles have been studied as metal-based drugs that may be used for biomedical applications due to the fact of their biocompatibility. Their physicochemical properties, which depend on synthesis techniques involving physical, chemical, biological, and microfluidic reactor methods affect biological activity in vitro and in vivo. Advanced tool-based physicochemical characterization is required to identify the biological and toxicological effects of ZnO nanoparticles. These nanoparticles have variable morphologies and can be molded into three-dimensional structures to enhance their performance. Zinc oxide nanoparticles have shown therapeutic activity against cancer, diabetes, microbial infection, and inflammation. They have also shown the potential to aid in wound healing and can be used for imaging tools and sensors. In this review, we discuss the synthesis techniques, physicochemical characteristics, evaluation tools, techniques used to generate three-dimensional structures, and the various biomedical applications of ZnO nanoparticles.

Pulse Duration and Wavelength Effects of Laser Ablation on the Oxidation, Hydrolysis, and Aging of Aluminum Nanoparticles in Water

We analyzed the formation of the aluminum (Al) nanoparticles (NPs) with triangular shape obtained by ablating Al bulk in liquid using pulses with different durations (5 ns, 200 ps, and 30 fs) and wavelengths (355 nm, 800 nm, and 1064 nm). We report three stages of synthesis and aging of Al NPs: Formation, transformation, and stable stage. The NPs prepared by different pulses are almost identical at the initial stage. The effects of duration and wavelength of the ablation pulses on the aging of NPs are revealed. Pulse duration is determined to be essential for morphological transformation of NPs, while pulse wavelength strongly influences particle sizes. NPs produced by ultra-short pulses have smaller sizes and narrow size distribution. We demonstrate that oxidation and hydrolysis of Al in water are the results of ablation for all pulse durations and wavelengths, which also strongly modify the preferable reaction path of NPs in water, thus affecting the composition and morphology of triangle NPs. The results of modeling of the NPs generation in water due to a 50 ps laser pulse interacting with a thick Al target are presented. Water-based effects in the formation of NPs, their evolution, and solidification are considered from the mechanical and thermophysical points of view. The detailed analysis of the modeling results allowed for determination of the main mechanism responsible for the ablation process followed by the NPs formation.

A simple post-synthesis conversion approach to Zn(OH)F and the effects of fluorine and hydroxyl on the photodegradation properties of dye wastewater

In this work, Zn(OH)F is prepared by an initiative, simple post-synthesis method, in which the molar ratio of F/Zn (R_F) was varied to investigate the effect of the NH₄F amounts added on the samples. Further, we have mainly investigated their energy bands and photochemical properties. Under UV light irradiation (λ£420nm), the samples (R_F=0,1,2) show the high degradation activities of methylene blue (MB) dye, namely, 80% of MB can be degraded after 8min. It is found that the hydroxyl and fluorine have greatly down shifted the conduction band (CB, 0.99eV) and valence band (VB, 4.17eV) of Zn(OH)F, compared with ZnO (CB=-0.31eV, VB=2.89eV), but with the nearly same band gap. For the degradation of MB dye, the main oxidative species are holes and hydroxyl radicals for ZnO and Zn(OH)F, respectively. This study suggests that this simple post-synthesis fluorination approach could be extended to develop the other photocatalysts; moreover, we can facilely tune the band structure and photocatalytic activity by introducing or removing hydroxyl and fluorine, which could benefit to develop new photocatalysts.

Does seed size and surface anatomy play role in combating phytotoxicity of nanoparticles?

Rapid utilization of nano-based products will inevitably release nanoparticles into the environment with unidentified consequences. Plants, being an integral part of ecosystem play a vital role in the incorporation of nanoparticles in food chain and thus, need to be critically assessed. The present study assesses the comparative phytotoxicity of nanoparticle, bulk and ionic forms of zinc at different concentrations on selected plant species with varying seed size and surface anatomy. ZnO nanoparticles were chosen in view of their wide spread use in cosmetics and health care products, which allow their direct release in the environment. The impact on germination rate, shoot & root length and vigour index were evaluated. A concentration dependent inhibition of seed germination as well as seedling length was observed in all the tested plants. Due to the presence of thick cuticle on testa and root, pearl millet (xerophytic plant) was found to be relatively less sensitive to ZnO nanoparticles as compared to wheat and tomato (mesophytic plants) with normal cuticle layer. No correlation was observed between nanoparticles toxicity and seed size. The results indicated that variations in surface anatomy of seeds play a crucial role in determining the phytotoxicity of nanoparticles. The present findings significantly contribute to assess potential consequences of nanoparticle release in environment particularly with major emphasis on plant systems. It is the first report which suggests that variations observed in phytotoxicity of nanoparticles is mainly due to the predominant differences in size and surface anatomy of tested plant seeds and root architecture. Effect of various concentrations of nano ZnO, bulk ZnO and zinc sulphate on the growth of pearl millet (A), tomato (B) and wheat (C) seedlings.

All Inorganic Halide Perovskites Nanosystem: Synthesis, Structural Features, Optical Properties and Optoelectronic Applications

The recent success of organometallic halide perovskites (OHPs) in photovoltaic devices has triggered lots of corresponding research and many perovskite analogues have been developed to look for devices with comparable performance but better stability. Upon the preparation of all inorganic halide perovskite nanocrystals (IHP NCs), research activities have soared due to their better stability, ultrahigh photoluminescence quantum yield (PL QY), and composition dependent luminescence covering the whole visible region with narrow line-width. They are expected to be promising materials for next generation lighting and display, and many other applications. Within two years, a lot of interesting results have been observed. Here, the synthesis of IHPs is reviewed, and their progresses in optoelectronic devices and optical applications, such as light-emitting diodes (LEDs), photodetectors (PDs), solar cells (SCs), and lasing, is presented. Information and recent understanding of their crystal structures and morphology modulations are addressed. Finally, a brief outlook is given, highlighting the presently main problems and their possible solutions and future development directions.

Ultrathin tin oxide layer-wrapped gold nanoparticles induced by laser ablation in solutions and their enhanced performances

A simple and flexible method of preparing an ultrathin semiconducting oxide layer-wrapped gold nanoparticles (NPs) is presented. The method is a single-step procedure based on laser ablation in a precursor solution. The spherical Au NPs (<20nm in mean size) wrapped with a SnO₂ layer of approximately 2nm in thickness are formed after the laser ablation of a gold target in SnCl₄ solutions with concentrations of 0.01-0.1M. The thickness of such SnO₂ shell is nearly independent of Au particle sizes. Results reveal that the formation of Au@SnO₂ NPs involves a two-step process: the laser ablation-induced formation of Au NPs and subsequent Coulomb effect-based colloidal attachment and self-assembly on the Au NPs. Au@SnO₂ NPs-built film exhibits significantly stronger surface-enhanced Raman scattering effect to organic phosphor molecules (phenylphosphonic acid) and much better gas sensing performance to H₂S at room temperature compared with the bare Au NPs and pure SnO₂ NPs films, respectively. This work presents a simple route to fabricating noble-metal NPs wrapped with symmetrical and ultrathin semiconducting oxide shells.

Laser Synthesis and Processing of Colloids: Fundamentals and Applications

Driven by functionality and purity demand for applications of inorganic nanoparticle colloids in optics, biology, and energy, their surface chemistry has become a topic of intensive research interest. Consequently, ligand-free colloids are ideal reference materials for evaluating the effects of surface adsorbates from the initial state for application-oriented nanointegration purposes. After two decades of development, laser synthesis and processing of colloids (LSPC) has emerged as a convenient and scalable technique for the synthesis of ligand-free nanomaterials in sealed environments. In addition to the high-purity surface of LSPC-generated nanoparticles, other strengths of LSPC include its high throughput, convenience for preparing alloys or series of doped nanomaterials, and its continuous operation mode, suitable for downstream processing. Unscreened surface charge of LSPC-synthesized colloids is the key to achieving colloidal stability and high affinity to biomolecules as well as support materials, thereby enabling the fabrication of bioconjugates and heterogeneous catalysts. Accurate size control of LSPC-synthesized materials ranging from quantum dots to submicrometer spheres and recent upscaling advancement toward the multiple-gram scale are helpful for extending the applicability of LSPC-synthesized nanomaterials to various fields. By discussing key reports on both the fundamentals and the applications related to laser ablation, fragmentation, and melting in liquids, this Article presents a timely and critical review of this emerging topic.

Facile synthesis and heteroepitaxial growth mechanism of Au@Cu core–shell bimetallic nanocubes probed by first-principles studies

This work provided a facile strategy for the synthesis of Au@Cu core–shell nanostructures. The proposed growth mechanism was probed by a first-principles investigation.

Surface Nanostructures Composed of Thiolated Cyclodextrin/Au and Fe Species: Gas- and Liquid-Phase Preparation

Supramolecular surface nanostructures have application potential as functional devices. The complex combination of thiolated cyclodextrin, chemisorbed on an Au surface (Au-S-CD), with deposited Fe species is studied by secondary ion mass spectrometry. The Fe species are prepared by pulsed laser ablation in water and thermal effusion in vacuum. Using laser ablation in water, the solution of Fe species is dropped on Au-S-CD, where mass peaks at 1227 m/z, 1243 m/z, and 1260 m/z are observed and assigned to C42 H68 O34 SNa-Fe(+) , C42 H68 O34 SK-Fe(+) together with C42 H68 O34 SNa-FeO(+) , and C42 H68 O34 SK-FeO(+) , respectively. On the other hand, laser ablation directly linked to the Au-S-CD surface results in desorption of CD-S. Thermal effusion, even with a cooled surface, was negative with respect to the complex observation. Laser ablation results in the formation of a supramolecular host-guest complex of the form Au-S-CD-Fe, and in the formation of an adduct of the form Au-S-CD-FeO.

Intense, stable and excitation wavelength-independent photoluminescence emission in the blue-violet region from phosphorene quantum dots

Nanoscale phosphorene quantum dots (PQDs) with few-layer structures were fabricated by pulsed laser ablation of a bulk black phosphorus target in diethyl ether. An intense and stable photoluminescence (PL) emission of the PQDs in the blue-violet wavelength region is clearly observed for the first time, which is attributed to electronic transitions from the lowest unoccupied molecular orbital (LUMO) to the highest occupied molecular orbital (HOMO) and occupied molecular orbitals below the HOMO (H-1, H-2), respectively. Surprisingly, the PL emission peak positions of the PQDs are not red-shifted with progressively longer excitation wavelengths, which is in contrast to the cases of graphene and molybdenum disulphide quantum dots. This excitation wavelength-independence is derived from the saturated passivation on the periphery and surfaces of the PQDs by large numbers of electron-donating functional groups which cause the electron density on the PQDs to be dramatically increased and the band gap to be insensitive to the quantum size effect in the PQDs. This work suggests that PQDs with intense, stable and excitation wavelength-independent PL emission in the blue-violet region have a potential application as semiconductor-based blue-violet light irradiation sources.

Semi-transparent all-oxide ultraviolet light-emitting diodes based on ZnO/NiO-core/shell nanowires

Semi-transparent all-oxide light-emitting diodes based on ZnO/NiO-core/shell nanowire structures were prepared on double-polished c-Al2O3 substrates. The entire heterojunction diode showed an average transparency of ∼65% in the ultraviolet and visible regions. Under forward bias, the diode displayed an intense ultraviolet emission at ∼382 nm, and its electroluminescence performance was remarkable in terms of a low emission onset, acceptable operating stability, and the ability to optically excite emissive semiconductor nanoparticle chromophores.

Controlled reverse pulse electrosynthesized spike-piece-structured Ni/Ni(OH)2 interlayer nanoplates for electrochemical pseudocapacitor applications

An ultrathin Ni/Ni(OH)2 hybrid electrode has been synthesized using a controlled reverse pulse modulated electrochemical approach and demonstrated as an advanced pseudocapacitor material having a remarkable specific capacitance and excellent cycling performance.

Luminescence mechanisms of defective ZnO nanoparticles

Thermal annealing effects on the emission properties of defective wurtzite-ZnO nanoparticles produced by laser ablation in water.

Smooth and solid WS2 submicrospheres grown by a new laser fragmentation and reshaping process with enhanced tribological properties

A novel laser induced fragmentation and reshaping (LFR) strategy is demonstrated to grow smooth and solid WS₂ submicrospheres with enhanced tribological properties.

Generation of silver titania nanoparticles from an Ag–Ti alloy via picosecond laser ablation and their antibacterial activities

In this work, a bulk Ti/Ag alloy was used, for the first time, to produce Ag–TiO₂ compound nanoparticles using picosecond laser ablation in deionised water.

In situ electron beam irradiation-driven formation of quantum dots

Recrystallization of amorphous materials is a very interesting phenomenon, but some transformation details are still unknown.

An insight into defect relaxation in metastable ZnO reflected by a unique luminescence and Raman evolutions

Defects play a crucial role in semiconductors, but a facile method to observe defect variation inside semiconductors is still absent.

Localized surface plasmon resonance of Cu nanoparticles by laser ablation in liquid media

Expanding localized surface plasmon resonance (LSPR) properties of colloidal copper nanoparticles by laser ablation in liquid (LAL) operated in ambient conditions were reported. The results may aid the application of copper LSPR in optical catalysis and detection devices.

Enhancement of pulsed laser ablation in environmentally friendly liquid

Enhancement of pulsed laser ablation can be achieved in acetic acid as an environmentally friendly liquid. This paper evaluates microholes and textured features induced by a nanosecond pulsed laser under different processing circumstances. The microholes are fabricated by laser drilling in acetic acid and found to be 100% deeper than in air. The textured features achieved in the liquid demonstrate a higher content of Copper and a lower content of Oxygen. The improvement of laser ablation efficiency in the liquid is attributed to the strong confinement of plasma plume accompanying with shockwave and cavitation bubbles. Meanwhile, the laser enhanced chemical etching by the weak acid plays a critical role.

Role of zinc interstitials and oxygen vacancies of ZnO in photocatalysis: a bottom-up approach to control defect density

Oxygen vacancies (V(O)s) in ZnO are well-known to enhance photocatalytic activity (PCA) despite various other intrinsic crystal defects. In this study, we aim to elucidate the effect of zinc interstitials (Zn(i)) and V(O)s on PCA, which has applied as well as fundamental interest. To achieve this, the major hurdle of fabricating ZnO with controlled defect density requires to be overcome, where it is acknowledged that defect level control in ZnO is significantly difficult. In the present context, we fabricated nanostructures and thoroughly characterized their morphological (SEM, TEM), structural (XRD, TEM), chemical (XPS) and optical (photoluminescence, PL) properties. To fabricate the nanostructures, we adopted atomic layer deposition (ALD), which is a powerful bottom-up approach. However, to control defects, we chose polysulfone electrospun nanofibers as a substrate on which the non-uniform adsorption of ALD precursors is inevitable because of the differences in the hydrophilic nature of the functional groups. For the first 100 cycles, Zn(i)s were predominant in ZnO quantum dots (QDs), while the presence of V(O)s was negligible. As the ALD cycle number increased, V(O)s were introduced, whereas the density of Zn(i) remained unchanged. We employed PL spectra to identify and quantify the density of each defect for all the samples. PCA was performed on all the samples, and the percent change in the decay constant for each sample was juxtaposed with the relative densities of Zn(i)s and V(O)s. A logical comparison of the relative defect densities of Zn(i)s and V(O)s suggested that the former are less efficient than the latter because of the differences in the intrinsic nature and the physical accessibility of the defects. Other reasons for the efficiency differences were elaborated.

Highly stable sub-5 nm Sn₆O₄(OH)₄ nanocrystals with ultrahigh activity as advanced photocatalytic materials for photodegradation of methyl orange

Among numerous active photocatalytic materials, Sn-based oxide nanomaterials are promising photocatalytic materials in environmental protection measures such as water remediation due to their excellent physicochemical property. Research on photocatalytic nanomaterials for photodegradation of methyl orange (MO) so far has focused on TiO₂-based nanostructures; e.g., TiO₂-P25 is recognized to be the best commercial photocatalyst to date, rather than Sn-based oxide nanomaterials, in spite of their impressive acid- and alkali-resistant properties and high stability. Here, we demonstrate very high photocatalytic activity of highly stable sub-5 nm hydromarchite (Sn₆O₄(OH)₄) nanocrystals synthesized by a simple and environmentally friendly laser-based technique. These Sn₆O₄(OH)₄ nanocrystals exhibit ultrahigh photocatalytic performance for photodegradation of MO and their degradation efficiency is far superior to that of TiO₂-P25. The detailed investigations demonstrated that the great photocatalytic activity results from the ultrafine size and unique surface activity induced by the laser-based technique. Mass production of reactive species of hydroxyl radicals was detected in the experiments due to the appropriate bandgap of Sn₆O₄(OH)₄ nanocrystals. These findings actually open a door to applications of Sn-based oxide nanomaterials as advanced photocatalytic materials.

Fabrication of gold nanoparticles by laser ablation in liquid and their application for simultaneous electrochemical detection of Cd2+, Pb2+, Cu2+, Hg2+

In this paper, we demonstrated the fabrication of high active and high sensitive Au nanoparticles by laser ablation in liquid (LAL) method, and their application in electrochemical detection of heavy metal ions. First, LAL method are used to fabricate Au nanoparticles in water in a clean way. Second, the Au nanoparticles were assembled onto the surface of the glassy carbon (GC) electrode by an electrophoretic deposition method to form an AuNPs/GC electrode for electrochemical characterization and detection. Through differential pulse anodic stripping voltammetry method, it shows that the AuNPs/GC electrode could be used for the simultaneous and selective electrochemical detection of Cd(2+), Pb(2+), Cu(2+), and Hg(2+). By studying the influence of test conditions to optimize the electrochemical detection, we can detect Cd(2+), Pb(2+), Cu(2+), and Hg(2+) simultaneously with a low concentration of 3 × 10(-7) M in the experiments.