A highly selective dual-signal response ratiometric fluorescence sensing strategy for malachite green in fish based on carbon dots/copper nanoclusters nanocomposite

Malachite green (MG), a widely used antiparasitic agent, poses health risks to human due to its genotoxic and carcinogenic properties. Herein, a stable dual-emission fluoroprobe of carbon dots/copper nanoclusters is prepared for highly selective detection of MG based on the inner filter effect. This probe exhibits characteristic emission bands at 435 and 625 nm when excited at 376 nm. After adding MG, the both emission signals were significantly quenched, and the ratio of fluorescence intensity (F435/F625) was linearly related to the concentration of MG in the range of 0.05-40 μmol L-1 with a limit of detection of 18.2 nmol L-1. Meanwhile, the two signals exhibit linear relationships with the concentration of MG, respectively, and the corresponding detection results were consistent. The fluoroprobe was successfully used for the detection of MG in fish samples with the recoveries ranging from 96.0% to 103.8% and a relative standard deviation of <3.3%.

Hydrogel composites based on chitosan and CuAuTiO2 photocatalysts for hydrogen production under simulated sunlight irradiation

This study explored the photocatalytic hydrogen evolution reaction (HER) using novel biohydrogel composites comprising chitosan, and a photocatalyst consisting in TiO2 P25 decorated with Au and/or Cu mono- and bimetallic nanoparticles (NPs) to boost its optical and catalytic properties. Low loads of Cu and Au (1 mol%) were incorporated onto TiO2 via a green photodeposition methodology. Characterization techniques confirmed the incorporation of decoration metals as well as improvements in the light absorption properties in the visible light interval (λ > 390 nm) and electron transfer capability of the semiconductors. Thereafter, Au and/or Cu NP-supported TiO2 were incorporated into chitosan-based physically crosslinked hydrogels revealing significant interactions between chitosan functional groups (hydroxyls, amines and amides) with the NPs to ensure its encapsulation. These materials were evaluated as photocatalysts for the HER using water and methanol mixtures under simulated sunlight and visible light irradiation. Sample CuAuTiO2/ChTPP exhibited a maximum hydrogen generation of 1790 μmol g-1 h-1 under simulated sunlight irradiation, almost 12-folds higher compared with TiO2/ChTPP. Also, the nanocomposites revealed a similar tendency under visible light with a maximum hydrogen production of 590 μmol g-1 h-1. These results agree with the efficiency of photoinduced charge separation revealed by transient photocurrent and EIS.

Laser Ablation for the Synthesis of Cu/Cu2O/CuO and Its Development as Photocatalytic Material for Escherichia coli Detoxification

Advanced Oxidation Processes (AOPs) offer promising methods for disinfection by generating radical species like hydroxyl radicals, superoxide anion radicals, and hydroxy peroxyl, which can induce oxidative stress and deactivate bacterial cells. Photocatalysis, a subset of AOPs, activates a semiconductor using specific electromagnetic wavelengths. A novel material, Cu/Cu2O/CuO nanoparticles (NPs), was synthesized via a laser ablation protocol (using a 1064 nm wavelength laser with water as a solvent, with energy ranges of 25, 50, and 80 mJ for 10 min). The target was sintered from 100 °C to 800 °C at rates of 1.6, 1.1, and 1 °C/min. The composite phases of Cu, CuO, and Cu2O showed enhanced photocatalytic activity under visible-light excitation at 368 nm. The size of Cu/Cu2O/CuO NPs facilitates penetration into microorganisms, thereby improving the disinfection effect. This study contributes to synthesizing mixed copper oxides and exploring their activation as photocatalysts for cleaner surfaces. The electronic and electrochemical properties have potential applications in other fields, such as capacitor materials. The laser ablation method allowed for modification of the band gap absorption and enhancement of the catalytic properties in Cu/Cu2O/CuO NPs compared to precursors. The disinfection of E. coli with Cu/Cu2O/CuO systems serves as a case study demonstrating the methodology's versatility for various applications, including disinfection against different microorganisms, both Gram-positive and Gram-negative.

The size-dependent valence and conduction band-edge energies of Cu quantum dots

Ultra-small metal particles having band gaps are regarded as a new class of functional materials. We investigated the size dependencies of the band-edge energies on Cu quantum-dots in the size range of 0.7-2.1 nm. The extremely high conduction band-edge energies owing to the strong quantum-size effects were observed for sizes below 1 nm.

Unveiling the Long-Lived Emission of Copper Nanoclusters Embedded in a Protein Scaffold

Protein-conjugated coinage metal nanoclusters have become promising materials for optoelectronics and biomedical applications. However, the origin of the photoluminescence, especially the long-lived excited state emission in these metal nanoclusters, is still elusive. Here, we unveiled the underlying mechanism of long-lived emission in albumin protein-conjugated copper nanoclusters (Cu NCs) using steady state and time-resolved spectroscopic techniques. Our findings reveal room-temperature phosphorescence (RTP) in protein-conjugated Cu NCs. Time-resolved area-normalized spectra distinguished short- and long-lived components, where the former arises from the singlet state and the latter from the triplet state, thus resulting in RTP. The similarity of the emission spectra at room (298 K) and cryogenic (77 K) temperature ascertains the RTP phenomenon by harvesting the higher-lying triplet states. Time-gated bioimaging of A549 cells using the long-lived emission not only supports RTP emission in the cellular environment but also provides exciting avenues in long-term bioimaging using bovine serum albumin-conjugated Cu NCs.

Bismuth Nano-Nest/Ti3CN Quantum Dot-Based Surface Plasmon Coupling Electrochemiluminescence Sensor for Ascites miRNA-421 Detection

In this study, a novel surface plasmon-coupled electrochemiluminescence (SPC-ECL) biosensor was developed based on bismuth nano-nest and Ti₃CN quantum dots (Ti₃CN QDs). First, MXene derivative QDs (Ti₃CN QDs) with excellent luminescence performance were prepared as the ECL luminescent. The N doping in Ti₃CN QDs can effectively improve the luminescence performance and catalytic activity. Therefore, the luminescence performance of QDs has been effectively improved. Furthermore, the bismuth nano-nest structure with a strong localized surface plasmon resonance effect has been designed as the sensing interface via the electrochemical deposition method. It was worth noticed that the morphology of bismuth nanomaterials can be controlled effectively on the electrode surface by the step potential method. Due to the abundant surface plasmon hot spots generated between the bismuth nano-nests, the isotropic ECL signal of Ti₃CN QDs can be not only significantly enhanced by 5.8 times but also converted into polarized emission. Finally, the bismuth nano-nest/Ti₃CN QD-based SPC-ECL sensor was used to quantify miRNA-421 in the range of 1 fM to 10 nM. The biosensor has been successfully used for miRNA in ascites samples from gastric cancer patients, which indicated that the SPC-ECL sensor developed in this study has great potential for clinical analysis.

An empirical experimental investigation on the effect of an external electric field on the behaviour of laser-induced cavitation bubbles

This study is an attempt to empirically investigate the behaviour of laser-induced cavitation bubbles under the influence of an external electric field. As such two targets (copper and iridium) were subjected to a high-power Nd:YAG laser beam while being submerged in a liquid. Three different liquids were chosen for this purpose viz. acetone, ethanol, and distilled de-ionized water. The choice of the liquids was made with the underlying assumption that the conductivity of the liquids would play a significant role in responding to the applied external electric field and thus dictate the behaviour of the cavitation bubbles. A probe-beam method known as a beam deflection setup was employed for this experiment and the results were analyzed using the Rayleigh-Plesset model. The results revealed that the maximum radii of the cavitation bubbles increased in response to an increasing electric field. This effect was more pronounced in the presence of acetone medium and decreased successively while using ethanol and water media owing to their varying magnitudes of electrical conductivity. The bubble collapse speeds and their energies were also measured and similar trends were observed in both cases. The results from cavitation bubble dynamics were then applied to a Gilmore model and the sizes of the NPs synthesized using laser ablation with and without an external electric field were calculated using classical nucleation theory.

Water Saturated with Pressurized CO2 as a Tool to Create Various 3D Morphologies of Composites Based on Chitosan and Copper Nanoparticles

Methods for creating various 3D morphologies of composites based on chitosan and copper nanoparticles stabilized by it in carbonic acid solutions formed under high pressure of saturating CO2 were developed. This work includes a comprehensive analysis of the regularities of copper nanoparticles stabilization and reduction with chitosan, studied by IR and UV-vis spectroscopies, XPS, TEM and rheology. Chitosan can partially reduce Cu2+ ions in aqueous solutions to small-sized, spherical copper nanoparticles with a low degree of polydispersity; the process is accompanied by the formation of an elastic polymer hydrogel. The resulting composites demonstrate antimicrobial activity against both fungi and bacteria. Exposing the hydrogels to the mixture of He or H2 gases and CO2 fluid under high pressure makes it possible to increase the porosity of hydrogels significantly, as well as decrease their pore size. Composite capsules show sufficient resistance to various conditions and reusable catalytic activity in the reduction of nitrobenzene to aniline reaction. The relative simplicity of the proposed method and at the same time its profound advantages (such as environmental friendliness, extra purity) indicate an interesting role of this study for various applications of materials based on chitosan and metals.

Plasmonic and Conductive Structures of TCO Films with Embedded Cu Nanoparticles

Cu nanoparticles were produced by using solid-state dewetting (dry) of a 1.3 nm Cu layer or laser ablation of a Cu solid target (wet) in acetone and methanol. The morphology and chemical composition of the nanoparticles were investigated as a function of the synthesis methods and their key parameters of the annealing temperature (200–500 °C) and the liquid environment during the ablation. Cu nanoparticles were then embedded in transparent conductive oxide (TCO) films as aluminum-doped zinc oxide (AZO) or zirconium-doped indium oxide (IZrO); the TCO_bott/Cu nanoparticle/TCO_top structures were synthesized with all combinations of AZO and IZrO as the top and bottom layers. The goal was to achieve a plasmonic and conductive structure for photovoltaic applications via a comparison of the involved methods and all fabricated structures. In particular, solid-state dewetting produced faceted or spherical (depending on the annealing temperature) nanoparticles with an average size below 150 nm while laser ablation produced spherical nanoparticles below 250 nm. Dry and wet plasmonic conductive structures as a function of the TCOs employed and the temperature of annealing could reach a sheet resistance of 86 Ω/sq. The energy band-gap E_gap, absorbance, transmittance, and reflectance of the plasmonic conductive structures were investigated in the UV–vis–NIR range. They showed a dependence on the sequence of the top and bottom TCO, with best transmittances of 89.4% for the dry plasmonic conductive structure and 84.7% for the wet plasmonic conductive structure. The latter showed a higher diffused transmittance of between 10–20% in the visible range.

Relative Populations and IR Spectra of Cu38 Cluster at Finite Temperature Based on DFT and Statistical Thermodynamics Calculations

The relative populations of Cu38 isomers depend to a great extent on the temperature. Density functional theory and nanothermodynamics can be combined to compute the geometrical optimization of isomers and their spectroscopic properties in an approximate manner. In this article, we investigate entropy-driven isomer distributions of Cu38 clusters and the effect of temperature on their IR spectra. An extensive, systematic global search is performed on the potential and free energy surfaces of Cu38 using a two-stage strategy to identify the lowest-energy structure and its low-energy neighbors. The effects of temperature on the populations and IR spectra are considered via Boltzmann factors. The computed IR spectrum of each isomer is multiplied by its corresponding Boltzmann weight at finite temperature. Then, they are summed together to produce a final temperature-dependent, Boltzmann-weighted spectrum. Our results show that the disordered structure dominates at high temperatures and the overall Boltzmann-weighted spectrum is composed of a mixture of spectra from several individual isomers.

Morphology, Electrical and Optical Properties of Cu Nanostructures Embedded in AZO: A Comparison between Dry and Wet Methods

Herein, Cu nanostructures are obtained by solid-state dewetting of 9 nm copper layer (dry) or by ablating copper target, using a nanosecond pulsed laser at 1064 nm, in acetone and isopropyl alcohol (wet). The Cu nanostructures are embedded in aluminum-doped zinc oxide layer. Then, the electrical, optical, and morphological properties of the two kinds of systems, as a function of their synthesis parameters, are investigated. The aim is to compare the two fabrication methods and select the main conditions to achieve the best system for photovoltaic applications. The main differences, exhibited by the wet and dry processes, were in the shape and size of the Cu nanostructures. Dewetting in nitrogen produces faceted nanoparticles, with an average size below 150 nm, while laser ablation originates spherical and smaller nanoparticles, below 50 nm. Dry system underwent to thermal annealing, which improves the electrical properties, compared to the wet system, with a sheet resistance of 10³ vs. 10⁶ Ω/sq, respectively; finally, the dry system shows a maximum transmittance of 89.7% at 697 nm, compared to the wet system in acetone, 88.4% at 647 nm, as well as in isopropyl alcohol, 86.9% at 686 nm. Moreover, wet systems show higher transmittance in NUV.

High-yield Synthesis and Hybridizations of Cu Microplates for Catalytic Applications

Because of their special geometrical features, which include a high specific surface area and high proportion of exposed surface atoms, two-dimensional (2D) metal nanostructures based on Au and Ag have...

Copper-Based Plasmonic Catalysis: Recent Advances and Future Perspectives

With the capability of inducing intense electromagnetic field, energetic charge carriers, and photothermal effect, plasmonic metals provide a unique opportunity for efficient light utilization and chemical transformation. Earth-abundant low-cost Cu possesses intense and tunable localized surface plasmon resonance from ultraviolet-visible to near infrared region. Moreover, Cu essentially exhibits remarkable catalytic performance toward various reactions owing to its intriguing physical and chemical properties. Coupling with light-harvesting ability and catalytic function, plasmonic Cu serves as a promising platform for efficient light-driven chemical reaction. Herein, recent advancements of Cu-based plasmonic photocatalysis are systematically summarized, including designing and synthetic strategies for Cu-based catalysts, plasmonic catalytic performance, and mechanistic understanding over Cu-based plasmonic catalysts. What's more, approaches for the enhancement of light utilization efficiency and construction of active centers on Cu-based plasmonic catalysts are highlighted and discussed in detail, such as morphology and size control, regulation of electronic structure, defect and strain engineering, etc. Remaining challenges and future perspectives for further development of Cu-based plasmonic catalysis are also proposed.

M. M. de Almeida J, Pastoriza-Santos I, C. C. Coelho L. Advances in Plasmonic Sensing at the NIR-A Review

Surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR) are among the most common and powerful label-free refractive index-based biosensing techniques available nowadays. Focusing on LSPR sensors, their performance is highly dependent on the size, shape, and nature of the nanomaterial employed. Indeed, the tailoring of those parameters allows the development of LSPR sensors with a tunable wavelength range between the ultra-violet (UV) and near infra-red (NIR). Furthermore, dealing with LSPR along optical fiber technology, with their low attenuation coefficients at NIR, allow for the possibility to create ultra-sensitive and long-range sensing networks to be deployed in a variety of both biological and chemical sensors. This work provides a detailed review of the key science underpinning such systems as well as recent progress in the development of several LSPR-based biosensors in the NIR wavelengths, including an overview of the LSPR phenomena along recent developments in the field of nanomaterials and nanostructure development towards NIR sensing. The review ends with a consideration of key advances in terms of nanostructure characteristics for LSPR sensing and prospects for future research and advances in this field.

Influences of copper-potassium ion exchange process on the optical bandgaps and spectroscopic properties of Cr3+/Yb3+ co-doped in lanthanum aluminosilicate glasses

In this study, lanthanum aluminosilicate glasses with compositions of 45SiO2-20Al2O3-12.5LaF3-10BaF2-9K2O-1Cr2O3-2.5Yb2O3 (SALBK) were prepared using the conventional melting method and copper-potassium ion exchange process. Influences of the ion exchange process between copper and potassium on the visible, upconversion, and near-infrared luminescence spectra of Cr3+/Yb3+ co-doped under excitations of 343, 490, and 980 nm LD were investigated. The EDS analysis of SALBK glasses was measured to confirm the presence of atoms in the glasses. The values of direct and indirect bandgaps of Cr3+/Yb3+ co-doped SALBK glasses were calculated and analyzed. Besides, the energy exchange processes between Cu+, Cu2+ ions, and Cr3+, Yb3+ ions were also proposed and discussed.

Update on Interfacial Charge Transfer (IFTC) Processes on Films Inactivating Viruses/Bacteria under Visible Light: Mechanistic Considerations and Critical Issues

This review presents an update describing binary and ternary semiconductors involving interfacial charge transfer (IFCT) in composites made up by TiO2, CuO, Ag2O and Fe2O3 used in microbial disinfection (bacteria and viruses). The disinfection mechanism, kinetics and generation of reactive oxygen species (ROS) in solution under solar/visible light are discussed. The surface properties of the photocatalysts and their active catalytic sites are described in detail. Pathogenic biofilm inactivation by photocatalytic thin films is addressed since biofilms are the most dangerous agents of spreading pathogens into the environment.

Recent Progress in Plasmonic Hybrid Photocatalysis for CO2 Photoreduction and C–C Coupling Reactions

Plasmonic hybrid nanostructures have been investigated as attractive heterogeneous photocatalysts that can utilize sunlight to produce valuable chemicals. In particular, the efficient photoconversion of CO2 into a stable hydrocarbon with sunlight can be a promising strategy to achieve a sustainable human life on Earth. The next step for hydrocarbons once obtained from CO2 is the carbon–carbon coupling reactions to produce a valuable chemical for energy storage or fine chemicals. For these purposes, plasmonic nanomaterials have been widely investigated as a visible-light-induced photocatalyst to achieve increased efficiency of photochemical reactions with sunlight. In this review, we discuss recent achievements involving plasmonic hybrid photocatalysts that have been investigated for CO and CO2 photoreductions to form multi-carbon products and for C–C coupling reactions, such as the Suzuki–Miyaura coupling reactions.

Binary Chiral Nanoparticles Exhibit Amplified Optical Activity and Enhanced Refractive Index Sensitivity

Metallic chiral nanoparticles (CNPs) with a nominal helical pitch (P) of sub-10 nm contain inherent chirality and are promisingly applied to diverse prominent enantiomer-related applications. However, the sub-wavelength P physically results in weak optical activity (OA) to prohibit the development of these applications. Herein, a facile method to amplify the CNPs' OA by alloying the host CNPs with metals through a three-step layer-by-layer glancing angle deposition (GLAD) method is devised. Promoted by the GLAD-induced heating effect, the solute metallic atoms diffuse into the host CNPs to create binary alloy CNPs. Chiral alloying not only induces the plasmonic OA of the diffused solute and the created alloys but also amplifies that of the host CNPs, generally occurring for alloying Ag CNPs with diverse metals (including Cu, Au, Al, and Fe) and alloying Cu CNPs with Ag. Furthermore, the chiral alloying leads to an enhancement of refractive index sensitivity of the CNPs. The alloy CNPs with amplified plasmonic OA pave the way for potentially developing important chirality-related applications in the fields of heterogeneous asymmetric catalysis, enantiodifferentiation, enantioseparation, biosensing, and bioimaging.

Chirality Transfer in Galvanic Replacement Reactions

Demand for the transfer of chirality from a pre-engineered nanoparticle to any other metal is of fundamental importance for developing a wide range of chirality-related applications. Herein, we show that binary alloy chiral nanoparticles (CNPs) with an engineerable composition can be formed from metallic CNPs with intrinsic structural chirality serving as sacrificial templates (STs), via a galvanic replacement reaction (GRR). This GRR-mediated chirality transfer is a general phenomenon and results in the formation of Cu-Ag CNPs with solid morphology and mesoporous CNPs made of Ag-Au, Ag-Pt, and Ag-Pd. Our study imposes a new component, i.e., structural chirality, on the GRR. The insights from our study improve our fundamental understanding of the GRR principle and devise a versatile method to generate mesoporous alloy CNPs for developing prominent chirality-related applications in asymmetric catalysis, enantiodifferentiation, enantioseparation, biodetection, and bioimaging.

SERS-Active Cu Nanoparticles on Carbon Nitride Support Fabricated Using Pulsed Laser Ablation

We report a single-step route to co-deposit Cu nanoparticles with a graphitic carbon nitride (gCN) support using nanosecond Ce:Nd:YAG pulsed laser ablation from a Cu metal target coated using acetonitrile (CH3CN). The resulting Cu/gCN hybrids showed strong optical absorption in the visible to near-IR range and exhibited surface-enhanced Raman or resonance Raman scattering (SERS or SERRS) enhancement for crystal violet (CV), methylene blue (MB), and rhodamine 6G (R6G) used as probe analyte molecules adsorbed on the surface. We have characterized the Cu nanoparticles and the nature of the gCN support materials using a range of spectroscopic, structural, and compositional analysis techniques.

Role of confining liquids on the properties of Cu@Cu2O nanoparticles synthesized by pulsed laser ablation and a correlative ablation study of the target surface

The effect of confining liquid on the properties of copper nanoparticles synthesized by pulsed laser ablation in two organic solvents, methanol and 2-propanol is investigated along with the effect of the laser irradiation time on the synthesized nanoparticles. To understand the role of confining liquids on the formation mechanism of the nanoparticles in different environments, the results obtained in the organic solvents are compared to those obtained in distilled water. The increase in the average size of the nanoparticles from 7-19 nm with the laser irradiation time from 15-60 minutes is accompanied by a shift in the plasmonic peak towards longer wavelength from 606-621 nm, respectively in methanol. In the case of nanoparticles synthesized in 2-propanol, the average size of the nanoparticles increases from 9-17 nm and there is a corresponding shift in the SPR peak from 581-601 nm, respectively. The increase in the size of the nanoparticles with the increase in irradiation time in the organic solvents is the reverse trend of that obtained for nanoparticles synthesized in distilled water. The range of the plasmonic peak positions is blue shifted for the nanoparticles synthesized in methanol and 2-propanol as compared to that of 626-641 nm for the nanoparticles synthesized in distilled water indicating the formation of insufficiently oxidized nanoparticles in organic solvents. Formation of core-shell spherical copper nanoparticles with carbon encapsulation in methanol and 2-propanol is another interesting observation. The origin of the dependence of properties of the synthesized nanoparticles on the ambient liquid lies in the way the laser beam interacts with the target surface in the ambient. A detailed ablation study on the laser produced crater in all the three liquids is carried out to understand the factors that affect the properties of the nanoparticles.

Tuning the Surface Plasmon Resonance of Lanthanum Hexaboride to Absorb Solar Heat: A Review

While traditional noble metal (Ag, Au, and Cu) nanoparticles are well known for their plasmonic properties, they typically only absorb in the ultraviolet and visible regions. The study of metal hexaborides, lanthanum hexaboride (LaB₆) in particular, expands the available absorbance range of these metals well into the near-infrared. As a result, LaB₆ has become a material of interest for its energy and heat absorption properties, most notably to those trying to absorb solar heat. Given the growing popularity of LaB₆, this review focuses on the advances made in the past decade with respect to controlling the plasmonic properties of LaB₆ nanoparticles. This review discusses the fundamental structure of LaB₆ and explains how decreasing the nanoparticle size changes the atomic vibrations on the surface and thus the plasmonic absorbance band. We explain how doping LaB₆ nanoparticles with lanthanide metals (Y, Sm, and Eu) red-shifts the absorbance band and describe research focusing on the correlation between size dependent and morphological effects on the surface plasmon resonance. This work also describes successes that have been made in dispersing LaB₆ nanoparticles for various optical applications, highlighting the most difficult challenges encountered in this field of study.

Tunable Localized Surface Plasmon Resonance and Broadband Visible Photoresponse of Cu Nanoparticles/ZnO Surfaces

Plasmonic Cu nanoparticles (NP) were successfully deposited on ZnO substrates by atomic layer deposition (ALD) owing to the Volmer-Weber island growth mode. An evolution from Cu NP to continuous Cu films was observed with an increasing number of ALD cycles. Real and imaginary parts of the NP dielectric functions, determined by spectroscopic ellipsometry using an effective medium approach, evidence a localized surface plasmon resonance that can be tuned between the visible and near-infrared ranges by controlling the interparticle spacing and size of the NP. The resulting Cu NP/ZnO device shows an enhanced photoresponse under white light illumination with good responsivity values, fast response times, and stability under dark/light cycles. The significant photocurrent detected for this device is related to the hot-electron generation at the NP surface and injection into the conduction band of ZnO. The possibility of tuning the plasmon resonance together with the photoresponsivity of the device is promising in many applications related to photodetection, photonics, and photovoltaics.

Twinned copper nanoparticles modulated with electrochemical deposition for in situ SERS monitoring

The SERS response of the Cu deposits depends on the deposition time and reaches its maximum value at about 150 s because of the formation of peanut-like copper particles.

Alloying copper and palladium nanoparticles by pulsed laser irradiation of colloids suspended in ethanol

Nanoparticles (NPs) of copper, palladium and Cu_0.8Pd_0.2 alloy have been prepared by pulsed laser ablation/irradiation in ethanol, by the second harmonic of a pulsed Nd : YAG laser (532 nm, ∼5 ns, 10 Hz). The monometallic NPs were synthesized by laser ablation of pure bulk targets immersed in ethanol and the alloyed ones by laser irradiation of stirred mixtures of suspended monometallic colloids. The suspensions were irradiated through two distinctive configurations, including lateral collimated and top focused beams that reached the corresponding fluences for NPs vaporization and for extensive plasma formation. The generated NPs were characterized by ultraviolet-visible absorption spectrometry, low and high-resolution transmission electron microscopy, energy-dispersive spectroscopy and selected area electron diffraction. The first fluence regime afforded the synthesis of alloyed NPs in the few nm diameter range, where alloying was somewhat disturbed by agglomeration, while the second led to larger size NPs and faster alloying, due to laser scattering by the plasma. These findings were supported and interpreted by the particle heating-melting-evaporation model. The approach developed here, assisted by the model and the various characterization methods, proved to control the alloying process and the size distribution of the NPs and to give the best indication for its progress.

Synthesis of alloyed copper palladium nanoparticles through lateral collimated and top focused laser irradiation of their suspended colloids in ethanol. These configurations allowed control of the extent of alloying at the nanoscale.

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.

Investigation of the in situ generation of oxide-free copper nanoparticles using pulsed-laser ablation of bulk copper in aqueous solutions of DNA bases

The pulsed-laser ablation method was used as a facile and green approach to prepare oxide-free copper nanoparticles, and was performed by laser ablation of a copper target in aqueous solutions of the DNA bases.