Dual-Plasmonic Gold@Copper Sulfide Core-Shell Nanoparticles: Phase-Selective Synthesis and Multimodal Photothermal and Photocatalytic Behaviors

Optimization of the Surfactant Ratio in the Formation of Penta-Twinned Seeds for Precision Synthesis of Gold Nanobipyramids with Tunable Plasmon Resonances

The synthesis of high-purity gold nano bipyramids (Au NBPs) with a narrow size distribution and tunable plasmon resonances is of great significance for plasmon resonance-related applications. However, the synthesis Au NBP approach involves multiple steps with many parameters that can affect the purity of the final product. In this work, we were devoted to studying the effect of the molar ratio between hexadecyltrimethylammonium chloride (CTAC) and sodium citrate tribasic dihydrate (CiNa3) on the seed formation stage. The results showed that the yield of Au NBP product has dramatically increased with the seed solution made from the molar ratio of CTAC:CiNa3 at 21:1. Furthermore, using this optimal seed, we can efficiently synthesize Au NBPs with various sizes by adjusting the concentration of the seed but keeping the rest of the parameters constant. In this study, the longitudinal localized surface plasmon resonances (LSPRs) of Au NBPs exhibit tunability beyond 450 nm across the visible and near-infrared regions from 774 to 1224 nm. We were able to successfully fine-tune the LSPRs of Au NBPs in the spectral region to become resonant with the excitation wavelengths of an 808 nm near-infrared (NIR) laser. The photothermal activities of Au NBPs were studied under 808 nm laser irradiation at ambient conditions. The present work demonstrates a paradigm for the synthesis of Au NBPs with tunable LSPRs in a precise and controllable manner, achieved by examining the surfactant ratios in the formation of penta-twinned seeds.

Bismuth-Tin Core-Shell Particles From Liquid Metals: A Novel, Highly Efficient Photothermal Material that Combines Broadband Light Absorption with Effective Light-to-Heat Conversion

This study presents a pioneering investigation of hybrid bismuth-tin (BiSn) liquid metal particles for photothermal applications. It is shown that the intrinsic core-shell structure of liquid metal particles can be instrumentalized to combine the broadband absorption characteristics of defect-rich nano-oxides and the high light-to-heat conversion efficiency of metallic particles. Even though bismuth or tin does not show any photothermal characteristics alone, optimization of the core-shell structure of BiSn particles leads to the discovery of novel, highly efficient photothermal materials. Particles with optimized structures can absorb 85% of broadband light and achieve over 90% photothermal conversion efficiency. It is demonstrated that these particles can be used as a solar absorber for solar water evaporation systems owing to their broadband absorption capability and become a non-carbon alternative enabling scalable applications. We also showcased their use in polymer actuators in which a near-infrared (NIR) response stems from their oxide shell, and fast heating/cooling rates achieved by the metal core enable rapid response and local movement. These findings underscore the potential of BiSn liquid metal-derived core-shell particles for diverse applications, capitalizing on their outstanding photothermal properties as well as their facile and scalable synthesis conditions.

Au Cluster-Nanoparticle Dual Coupling for Photocatalytic CO2 Conversion

CO2-selective photoreduction to value-added products is ideal, but its practical application suffers from weak photogenerated carrier separation and insufficient multielectron transport. Herein, we constructed the tricomponent AuNPs@SnO2-AuNCs hybrid by decorating Au nanoclusters (AuNCs) on the Au nanoparticle (AuNPs)@SnO2 core-shell structure. AuNC-NP dual coupling endowed AuNPs@SnO2-AuNCs with an excellent CO yield of 64.8 μmol g-1 h-1 during CO2 photoreduction, which was higher than the role of separate application of AuNCs (25.3 μmol g-1 h-1) and AuNPs (16.0 μmol g-1 h-1). It was mainly attributed that the coaction of AuNPs and AuNCs not only enhanced the visible light absorption capacity but also improved the photogenerated carrier separation/migration. As a result, the electron-rich AuNCs induced from plasmonic AuNPs and photoexcited SnO2 promoted the photocatalytic CO2-to-CO performance. This work provides a new perspective to design multicomponent photocatalysts for highly efficient CO2 conversion.

Ligand exchange induced crystal structure and morphology evolution of copper-tin-sulfur binary and ternary compounds

In this manuscript, a simple one-pot heat-up method has been used to prepare multi-component copper-tin-sulfur nanomaterials, including binary Cu1.94S, ternary Cu4SnS4, and Cu1.94S/Cu4SnS4 nanocrystals by varying the reaction temperature, reaction time, and the type of copper source. Post-synthetic ligand exchange (LE) has further been introduced to replace the long-chain ligands originating from 1-dodecanethiol. It has been found that the LE process not only changes the surface ligands but also significantly affects the crystal structure and optical properties of nanocrystals. After LE, the crystal structures of Cu1.94S and Cu4SnS4 transformed to Cu7S4 and Cu3SnS4, respectively, with the Cu1.94S/Cu4SnS4 nanocrystals showing the same trend. This phenomenon could be ascribed to the loss of Cu+ originating from the strong complexation of Cu+ and ammonia with the formation of [Cu(NH3)n]2+ ions under aerobic conditions. Proton nuclear magnetic resonance (1H NMR) has been used to characterize the ligands on the surface before and after LE, which further demonstrated that the -SH was replaced during LE. Meanwhile, the band gaps of the obtained nanocrystals after LE show an obvious shift in the near-infrared region due to the evolution of crystal structures. This study will provide useful guidance for the LE of nanocrystals and the application of copper-based sulfide nanomaterials in optoelectronics and other fields.

Self-assembled hollow CuS@AuNRs/PDA nanohybrids with synergistically enhanced photothermal efficiency

The design of multifunctional nanocarriers with enhanced photothermal efficiency is of great significance for the photothermal therapy of cancer. In this study, hollow CuS@gold nanorods/polydopamine (HCuS@AuNRs/PDA) nanohybrids with synergistically enhanced photothermal efficiency were prepared by electrostatic self-assembly method. The high photothermal conversion efficiency of HCuS@AuNRs (55.88%) is attributed to the interfacial electron transfer between CuS and AuNRs, as well as the increase in free charge carrier concentration. The excellent adhesion performance and strong negative charge of PDA ensure a high doxorubicin hydrochloride (DOX) loading efficiency of 96.08% for HCuS@AuNRs/PDA. In addition, HCuS@AuNRs/PDA reveals outstanding NIR/pH dual-responsive drug release properties owing to the weakened interaction between PDA and DOX in acidic media and the distinct NIR responsiveness of HCuS@AuNRs. In vitro cell viability results confirm that HCuS@AuNRs/PDA could efficiently kill tumor cells under the dual effect of acidic media and NIR laser. This study presents a novel nanocarrier with synergistically enhanced NIR photothermal responsiveness and high drug loading capacity, which provides a versatile platform in intelligent drug release and photothermal therapy.

Influence of Surface Chemistry on Metal Deposition Outcomes in Copper Selenide-Based Nanoheterostructure Synthesis

The use of nanoparticle surface chemistry to direct metal deposition has been well-studied in the modification of metal nanoparticle substrates but is not yet well-established for metal chalcogenide particle substrates, although integration of these particles into nanoheterostructures is of high interest. In this report, we investigate the effect of Cu2-xSe surface chemistry on the morphology of metal deposition on these plasmonic semiconductor nanoparticles. Specifically, we functionalize Cu2-xSe nanoparticles with a suite of 12 different ligands and investigate how different aspects of the ligand structure do or do not impact the morphology and extent of subsequent metal deposition on the Cu2-xSe surface. Surprisingly, our results indicate that the morphology of the resulting metal deposits and the extent of metal deposition onto the existing Cu2-xSe particle substrate are indistinguishable for the majority of ligands tested. An exception to these findings is observed for particles functionalized by quaternary alkylammonium bromides, which exhibit statistically distinct metal deposition patterns compared to all other ligands tested. We hypothesize that this unique behavior is due to a cooperative binding mechanism of the quaternary alkylammonium bromides to the surface of copper selenide. Taken together, these results yield both new strategies for controlling postsynthetic modification of copper selenide nanoparticles and also reveal limitations of surface chemistry-based approaches for this system.

Dual-plasmonic CuS@Au heterojunctions synergistic enhanced photothermal and colorimetric dual signal for sensitive multiplexed LFIA

Multiplexed immunodetection, which achieves qualitative and quantitative outcomes for multiple targets in a single-run process, provides more sufficient results to guarantee food safety. Especially, lateral flow immunoassay (LFIA), with the ability to offer multiple test lines for analytes and one control line for verification, is a forceful candidate in multiplexed immunodetection. Nevertheless, given that single-signal mode is incredibly vulnerable to interference, further efforts should be engrossed on the combination of multiplexed immunodetection and multiple signals. Photothermal signal has sparked significant excitement in designing immunosensors. In this work, by optimizing and comparing the amount of gold, CuS@Au heterojunctions (CuS@Au HJ) were synthesized. The dual-plasmonic metal-semiconductor hybrid heterojunction exhibits a synergistic photothermal performance by increasing light absorption and encouraging interfacial electron transfer. Meanwhile, the colorimetric property is synergistic enhanced, which is conducive to reduce the consumption of antibodies and then improve assay sensitivity. Therefore, CuS@Au HJ are suitable to be constructed in a dual signal and multiplexed LFIA (DSM-LFIA). T-2 toxin and deoxynivalenol (DON) were used as model targets for the simulated multiplex immunoassay. In contrast to colloidal gold-based immunoassay, the built-in sensor has increased sensitivity by ≈ 4.42 times (colorimetric mode) and ≈17.79 times (photothermal mode) for DON detection and by ≈ 1.75 times (colorimetric mode) and ≈13.09 times (photothermal mode) for T-2 detection. As a proof-of-concept application, this work provides a reference to the design of DSM-LFIA for food safety detection.

Harmonic Generation up to Fifth Order from Al/Au/CuS Nanoparticle Films

Dual heterostructures integrating noble-metal and copper chalcogenide nanoparticles have attracted a great deal of attention in nonlinear optics, because coupling of their localized surface plasmon resonances (LSPRs) substantially enhances light-matter interactions through local-field effects. Previously, enhanced cascaded third-harmonic generation was demonstrated in Au/CuS heterostructures mediated by harmonically coupled surface plasmon resonances. This suggests a promising approach for extending nonlinear enhancement to higher harmonics by adding an additional nanoparticulate material with higher-frequency harmonic resonances to the hybrid films. Here we report the first observation of enhanced cascaded fourth- and fifth-harmonic generation in Al/Au/CuS driven by coupled LSPRs at the fundamental (1050 nm), second harmonic (525 nm), and third harmonic (350 nm) of the pump frequency. An analytical model based on incoherent dipole-dipole interactions among plasmonic nanoparticles accounts for the observed enhancements. The results suggest a novel design for efficiently generating higher harmonics in resonant plasmonic structures by means of multiple sum-frequency cascades.

A Mechanism Underpinning the Bioenergetic Metabolism-Regulating Function of Gold Nanocatalysts

Bioenergetic deficits are known to be significant contributors to neurodegenerative diseases. Nevertheless, identifying safe and effective means to address intracellular bioenergetic deficits remains a significant challenge. This work provides mechanistic insights into the energy metabolism-regulating function of colloidal Au nanocrystals, referred to as CNM-Au8, that are synthesized electrochemically in the absence of surface-capping organic ligands. When neurons are subjected to excitotoxic stressors or toxic peptides, treatment of neurons with CNM-Au8 results in dose-dependent neuronal survival and neurite network preservation across multiple neuronal subtypes. CNM-Au8 efficiently catalyzes the conversion of an energetic cofactor, nicotinamide adenine dinucleotide hydride (NADH), into its oxidized counterpart (NAD+ ), which promotes bioenergy production by regulating the intracellular level of adenosine triphosphate. Detailed kinetic measurements reveal that CNM-Au8-catalyzed NADH oxidation obeys Michaelis-Menten kinetics and exhibits pH-dependent kinetic profiles. Photoexcited charge carriers and photothermal effect, which result from optical excitations and decay of the plasmonic electron oscillations or the interband electronic transitions in CNM-Au8, are further harnessed as unique leverages to modulate reaction kinetics. As exemplified by this work, Au nanocrystals with deliberately tailored structures and surfactant-free clean surfaces hold great promise for developing next-generation therapeutic agents for neurodegenerative diseases.

Enhanced Photothermal Effect Assisted by Resonance Energy Transfer in Carbon/Covellite Core-Shell Nanoparticles toward a High-Performance Interfacial Water Evaporation Process

Carbon and semiconductor nanoparticles are promising photothermal materials for various solar-driven applications. Inevitable recombination of photoinduced charge carriers in a single constituent, however, hinders the realization of a greater photothermal effect. Core-shell heterostructures utilizing the donor-acceptor pair concept with high-quality interfaces can inhibit energy loss from the radiation relaxation of excited species, thereby enhancing the photothermal effect. Here, core-shell structures composed of a covellite (CuS) shell (acceptor) and spherical carbon nanoparticle (CP) core (donor) (abbreviated as CP/CuS) are proposed to augment the photothermal conversion efficiency via the Förster resonance energy transfer (FRET) mechanism. The close proximity and spectral overlap of the donor and acceptor trigger the FRET mechanism, where the electronic excitation relaxation energy of the CP reinforces the plasmonic resonance and near-infrared absorption in CuS, resulting in boosting the overall photothermal conversion efficiency. CP/CuS core-shell coated on polyurethane (PU) foam exhibits a total solar absorption of 97.1%, leading to an elevation in surface temperature of 61.6 °C in dry conditions under simulated solar illumination at a power density of 1 kW m-2 (i.e., 1 sun). Leveraging the enhanced photothermal conversion emanated from the energy transfer effect in the core-shell structure, CP/CuS-coated PU foam achieves an evaporation rate of 1.62 kg m-2 h-1 and an energy efficiency of 93.8%. Thus, amplifying photothermal energy generation in core-shell structures via resonance energy transfer can be promising in solar energy-driven applications and thus merits further exploration.

Plasmonic Ag@Cu2O core-shell nanostructures exhibiting near-infrared photothermal effect

This work was devoted to the investigation of the optical properties, structural characterization, and photothermal conversion performance of Ag@Cu2O nanostructures. The selection of anisotropic silver core, specifically Ag nanocubes, was driven by the possibility to tune LSPR across a broader range of the electromagnetic spectrum. The thickness of the Cu2O shell was intentionally changed through the variation in the Cu salt to the metal core nanoparticles ratios. The LSPRs of Ag(nanocube)@Cu2O core-shell nanoparticles can be fine-tuned to the spectral region to become resonant with the excitation wavelengths of 808 nm NIR laser. Due to the high refractive index of the deposited Cu2O, the redshifts of the plasmon band wavelength in the extinction spectra were observed. Consequently, the photothermal activities of the Ag(nanocube)@Cu2O core-shell NPs have been controlled by the shell thickness at the nanoscale. Ag@Cu2O nanoparticles with thickest shell (∼70 nm) exhibit the most efficient NIR photothermal effect under the irradiation of 808 nm laser at ambient conditions. Results of this work demonstrate that Ag@Cu2O hetero-nanostructures may be optimized and used for the efficient transformation of light into other forms of energy, specifically heat.

Plasmon-Induced Charge Transfer-Enhanced Raman Scattering on a Semiconductor: Toward Amplification-Free Quantification of SARS-CoV-2

Semiconductors demonstrate great potentials as chemical mechanism-based surface-enhanced Raman scattering (SERS) substrates in determination of biological species in complex living systems with high selectivity. However, low sensitivity is the bottleneck for their practical applications, compared with that of noble metal-based Raman enhancement ascribed to electromagnetic mechanism. Herein, a novel Cu2 O nanoarray with free carrier density of 1.78×1021  cm-3 comparable to that of noble metals was self-assembled, creating a record in enhancement factor (EF) of 3.19×1010 among semiconductor substrates. The significant EF was mainly attributed to plasmon-induced hot electron transfer (PIHET) in semiconductor which was never reported before. This Cu2 O nanoarray was subsequently developed as a highly sensitive and selective SERS chip for non-enzyme and amplification-free SARS-CoV-2 RNA quantification with a detection limit down to 60 copies/mL within 5 min. This unique Cu2 O nanoarray demonstrated the significant Raman enhancement through PIHET process, enabling rapid and sensitive point-of-care testing of emerging virus variants.

Plasmonic Cu2-xSe Mediated Colorimetric/Photothermal Dual-Readout Detection of Glutathione

Plasmonic nanomaterials have attracted great attention in the field of catalysis and sensing for their outstanding electrical and optical properties. Here, a representative type of nonstoichiometric Cu_2-xSe nanoparticles with typical near-infrared (NIR) localized surface plasma resonance (LSPR) properties originating from their copper deficiency was applied to catalyze the oxidation of colorless TMB into their blue product in the presence of H₂O₂, indicating they had good peroxidase-like activity. However, glutathione (GSH) inhibited the catalytic oxidation of TMB, as it can consume the reactive oxygen species. Meanwhile, it can induce the reduction of Cu(II) in Cu_2-xSe, resulting in a decrease in the degree of copper deficiency, which can lead to a reduction in the LSPR. Therefore, the catalytic ability and photothermal responses of Cu_2-xSe were decreased. Thus, in our work, a colorimetric/photothermal dual-readout array was developed for the detection of GSH. The linear calibration for GSH concentration was in the range of 1-50 μM with the LOD as 0.13 μM and 50-800 μM with the LOD as 39.27 μM. To evaluate the practicability of the assay, tomatoes and cucumbers were selected as real samples, and good recoveries indicated that the developed assay had great potential in real applications.

NIR II light response-based PDA/AuPt@CuS composites: Simultaneous readout of temperature and pressure sensing strategy for portable detection of pathogenic bacteria

In this study, we developed a simultaneous readout of pressure and temperature dual-signals platform based on the second near-infrared (NIR II) light response-based polydopamine (PDA)-functionalized-AuPt nanoparticles (NPs)@CuS nanosheets (PDA/AuPt@CuS NS) composite. Due to the excellent NIR photothermal performance of PDA/AuPt@CuS NS, it contribute to the decomposition of H₂O₂ and NH₄HCO₃ to generate gases (including O₂, CO₂, and NH₃₎ can be promoted, which can amplify the pressure signals in a sealed container. A sandwich mode is formed between Fe₃O₄ NPs and PDA/AuPt@CuS NS based on the dual-aptamer when target pathogenic bacteria is present. And, it is possible to convert the molecular recognition signals between the dual-aptamers into amplified pressures and temperatures, which can be read out by a portable pressure meter and smartphones simultaneously. It may offer the possibility for quantitative POCT analysis of Pathogenic Bacteria. Moreover, because of the high photothermal efficiency of this method, the developed dual-mode method can achieve that following the detection of bacteria and killing them immediately. As a result, secondary contamination is eliminated and bacterial transmission is avoided. The developed dual-signal sensing platform is also inexpensive, simple to operate and rapidly, indicating that it can be used for food safety analysis, clinical applications, and environmental monitoring.

Recent Advances and Perspectives of Core-Shell Nanostructured Materials for Photocatalytic CO2 Reduction

Photocatalytic CO₂ conversion into solar fuels is a promising technology to alleviate CO₂ emissions and energy crises. The development of core-shell structured photocatalysts brings many benefits to the photocatalytic CO₂ reduction process, such as high conversion efficiency, sufficient product selectivity, and endurable catalyst stability. Core-shell nanostructured materials with excellent physicochemical features take an irreplaceable position in the field of photocatalytic CO₂ reduction. In this review, the recent development of core-shell materials applied for photocatalytic reduction of CO_{2 is introduced} . First, the basic principle of photocatalytic CO₂ reduction is introduced. In detail, the classification and synthesis techniques of core-shell catalysts are discussed. Furthermore, it is also emphasized that the excellent properties of the core-shell structure can greatly improve the activity, selectivity, and stability in the process of photocatalytic CO₂ reduction. Hopefully, this paper can provide a favorable reference for the preparation of efficient photocatalysts for CO₂ reduction.

Probing Bidirectional Plasmon-Plasmon Coupling-Induced Hot Charge Carriers in Dual Plasmonic Au/CuS Nanocrystals

Heterostructured Au/CuS nanocrystals (NCs) exhibit localized surface plasmon resonance (LSPR) centered at two different wavelengths (551 and 1051 nm) with a slight broadening compared to respective homostructured Au and CuS NC spectra. By applying ultrafast transient absorption spectroscopy we show that a resonant excitation at the respective LSPR maxima of the heterostructured Au/CuS NCs leads to the characteristic hot charge carrier relaxation associated with both LSPRs in both cases. A comparison of the dual plasmonic heterostructure with a colloidal mixture of homostructured Au and CuS NCs shows that the coupled dual plasmonic interaction is only active in the heterostructured Au/CuS NCs. By investigating the charge carrier dynamics of the process, we find that the observed interaction is faster than phononic or thermal processes (< 100 fs). The relaxation of the generated hot charge carriers is faster for heterostructured nanocrystals and indicates that the interaction occurs as an energy transfer (we propose Landau damping or interaction via LSPR beat oscillations as possible mechanisms) or charge carrier transfer between both materials. Our results strengthen the understanding of multiplasmonic interactions in heterostructured Au/CuS NCs and will significantly advance applications where these interactions are essential, such as catalytic reactions.

Highly Responsive Plasmon Modulation in Dopant-Segregated Nanocrystals

Electron transfer to and from metal oxide nanocrystals (NCs) modulates their infrared localized surface plasmon resonance (LSPR), revealing fundamental aspects of their photophysics and enabling dynamic optical applications. We synthesized and chemically reduced dopant-segregated Sn-doped In₂O₃ NCs, investigating the influence of radial dopant segregation on LSPR modulation and near-field enhancement (NFE). We found that core-doped NCs show large LSPR shifts and NFE change during chemical titration, enabling broadband modulation in LSPR energy of over 1000 cm^-1 and of peak extinction over 300%. Simulations reveal that the evolution of the LSPR spectra during chemical reduction results from raising the surface Fermi level and increasing the donor defect density in the shell region. These results establish dopant segregation as a useful strategy to engineer the dynamic optical modulation in plasmonic semiconductor NC heterostructures going beyond what is possible with conventional plasmonic metals.

A robust Au@Cu2-xS nanoreactor assembled by silk fibroin for enhanced intratumoral glucose depletion and redox dyshomeostasis

Intracellular redox dyshomeostasis promoted by tumor microenvironment (TME) modulation has become an appealing therapeutic target for cancer management. Herein, a dual plasmonic Au/SF@Cu_2-xS nanoreactor (abbreviation as ASC) is elaborately developed by covalent immobilization of sulfur defective Cu_2-xS nanodots onto the surface of silk fibroin (SF)-capped Au nanoparticles. Tumor hypoxia can be effectively alleviated by ASC-mediated local oxygenation, owing to the newfound catalase-mimic activity of Cu_2-xS. The semiconductor of Cu_2-xS with narrow bandgap energy of 2.54 eV enables a more rapid dissociation of electron-hole (e^-/h⁺) pair for a promoted US-triggered singlet oxygen (¹O₂) generation, in the presence of Au as electron scavenger. Moreover, Cu_2-xS is devote to Fenton-like reaction to catalyze H₂O₂ into ·OH under mild acidity and simultaneously deplete glutathione to aggravate intracellular oxidative stress. In another aspect, Au nanoparticles with glucose oxidase-mimic activity consumes intrinsic glucose, which contributes to a higher degree of oxidative damage and energy exhaustion of cancer cells. Importantly, such tumor starvation and ¹O₂ yield can be enhanced by Cu_2-xS-catalyzed O₂ self-replenishment in H₂O₂-rich TME. ASC-initiated M1 macrophage activation and therapy-triggered immunogenetic cell death (ICD) favors the systematic tumor elimination by eliciting antitumor immunity. This study undoubtedly enriches the rational design of SF-based nanocatalysts for medical utilizations.

Facile aqueous synthesis of hollow dual plasmonic hetero-nanostructures with tunable optical responses through nanoscale Kirkendall effects

Herein, we report the colloidal synthesis of hollow dual-plasmonic nanoparticles (NPs) using Au@Cu₂O core-shell NPs as templates and exploiting the nanoscale Kirkendall effect. In our synthesis, we used organic compounds as a source of chalcogenide ions for an anion exchange reaction at elevated temperatures using polyvinylpyrrolidone (PVP) as a capping reagent to transform the solid Cu₂O shell into a hollow copper chalcogenide shell. The resulting structures possess different features depending on the chalcogenide precursor employed. TEM images confirm the complete transformation of Au@Cu₂O templates when 1,1-dimethyl-2-selenourea was added and the formation of hollow Au@Cu_2-x Se nanostructures. In contrast, residues of Cu₂O attached to the Au core were present when thioacetamide was used for the synthesis of Au@Cu_2-x S with all other conditions kept the same. The divergence of architectures caused distinct optical properties of Au@Cu_2-x S and Au@Cu_2-x Se NPs. This synthetic approach is an effective pathway for maneuvering the size of interior voids by varying the concentration of chalcogenide ions in the reaction mixture. The insights gained from this work will enrich the synthetic toolbox at the nanoscale and guide us on the rational design of multicomponent plasmonic nanoparticles with precisely controlled hollow interiors and sophisticated geometries, further enhancing our capabilities to fine-tune the electronic, optical, compositional, and physicochemical properties.

Plasmonic colloidal Au nanoparticles in DMSO: a facile synthesis and characterisation

We report a new pathway for the synthesis of plasmonic gold nanoparticles (Au NPs) in a bio-compatible medium. A modified room temperature approach based on the standard Turkevich synthesis, using sodium citrate as a reducing and stabilizing agent, results in a highly stable colloidal suspension of Au NPs in dimethyl sulfoxide (DMSO). The mean NP size of about 15 nm with a fairly low size distribution is revealed by scanning electron microscopy. The stability test through UV-vis absorption spectroscopy indicates no sign of aggregation for months. The Au NPs are also characterized by X-ray photoelectron, Raman scattering, and FTIR spectroscopies. The stabilisation mechanism of the Au NPs in DMSO is concluded to be similar to that of NPs synthesized in water. The Au NPs obtained in this work are applicable as SERS substrates, as proved by common analytes. In terms of bio-applications, they do not possess such side-effects as pronounced antibacterial activity, based on the tests performed on non-pathogenic Gram-positive or Gram-negative bacteria.

Anisotropic dual-plasmonic hetero-nanostructures with tunable plasmonic coupling effects

The influence of plasmonic coupling effects between different components in Au NRs@Cu2-x Se nanostructures on their characteristics was studied. To this aim, anisotropic Au@Cu2-x Se hetero-nanostructures with well-controlled design and optical properties were obtained. The LSPR bands of gold and copper selenide are superpositioned in the NIR region, resulting in superior photocatalytic properties of the nanostructures.

Hierarchical CuS@ZnIn2S4 Hollow Double-Shelled p-n Heterojunction Octahedra Decorated with Fullerene C60 for Remarkable Selectivity and Activity of CO2 Photoreduction into CH4

In this work, a hollow double-shelled architecture, based on n-type ZnIn₂S₄ nanosheet-coated p-type CuS hollow octahedra (CuS@ZnIn₂S₄ HDSOs), is designed and fabricated as a p-n heterojunction photocatalyst for selective CO₂ photoreduction into CH₄. The resulting hybrids provide rich active sites and effective charge migration/separation to drive CO₂ photoreduction, and meanwhile, CO detachment is delayed to increase the possibility of eight-electron reactions for CH₄ production. As expected, the optimized CuS@ZnIn₂S₄ HDSOs manifest a CH₄ yield of 28.0 μmol g^-1 h^-1 and a boosted CH₄ selectivity up to 94.5%. The decorated C₆₀ both possesses high electron affinity and improves catalyst stability and CO₂ adsorption ability. Thus, the C₆₀-decorated CuS@ZnIn₂S₄ HDSOs exhibit the highest CH₄ evolution rate of 43.6 μmol g^-1 h^-1 and 96.5% selectivity. This work provides a rational strategy for designing and fabricating efficient heteroarchitectures for CO₂ photoreduction.

Cu2-x Sx Capped AuCu Nanostars for Efficient Plasmonic Photothermal Tumor Treatment in the Second Near-Infrared Window

Plasmonic nanohybrids are promising photo energy conversion materials in photoelectronics and biomedicine, due to their unique surface plasmon resonance (SPR). Au and Cu_2-x S_x nanostructures with strong SPR in the near-infrared (NIR) spectral region are classic plasmonic systems used to convert NIR photons into heat for photothermal therapy (PTT). The rational design of the Au/Cu_2-x S_x nanohybrids is expected to induce better photothermal conversion; however, the construction of such hybrids via wet-chemistry methods with a well-controlled interfacial structure is still challenging. Here, the synthesis of an AuCu Star/Cu_2-x S_x nanohybrid is reported, where the Cu_2-x S_x components are selectively grown on the AuCu nanostar tips to form "caps". The spatial formation of the Cu_2-x S_x caps on star tips is mainly governed by surfactant concentration, tip curvature, and experimental manipulation. The nanohybrids show low cytotoxicity and superior photothermal conversion efficiency, enabling robust PTT to kill cancer cells in the second NIR window. Numerical simulation reveals that the coupling of Cu_2-x S_x on nanostar tips generates strong interfacial electric field, improving photothermal conversion. Moreover, the spatial separation structure favors the continuous flow of hot charge carriers to produce active radicals, further promoting the tumor treatment effect.

Scalable Fabrication of Conjugated Microporous Polymer Sponges for Efficient Solar Steam Generation

Seawater evaporation realized by solar-thermal conversion represents one of the most sustainable and effective strategies to obtain fresh water. Many approaches have been proposed to achieve high efficiencies of solar-thermal conversion, but their practical applications are limited by the low scalability. Herein, novel porphyrin/aniline-based conjugated microporous polymers (PACMPs) are synthesized via a Buchwald-Hartwig coupling reaction, which are then integrated with polyurethane sponges via a simple dip-coating technique. The PACMP-modified sponges (PACSs) retain the high porosity of the sponge substrate and excellent solar-thermal conversion properties of PACMPs. Under standard solar irradiation (1 kW m^-2), PACSs achieve a high seawater evaporation rate of 1.31 kg m^-2 h^-1 with a solar-thermal conversion efficiency of 86.3%. PACSs show no salt accumulation and high performance of desalination and dye decolorization, removing >99.9% salt and >99.2% dye, respectively. The self-floating characteristic, recyclability, and durable solar-thermal evaporation efficiencies enable PACSs to be promising candidate materials for seawater desalination and sewage purification.

Au-Cu2-xTe Plasmonic Heteronanostructure Photoelectrocatalysts

Semiconductor nanocrystals coupled with plasmonic Au nanoparticles have been widely studied as photoelectrocatalysts for solar water splitting. Among these, heterostructures of copper chalcogenides with Au remained a unique category for their dual plasmon character. However, while sulfides and selenides of copper have been extensively reported, heterostructures of copper tellurides with Au have not been explored. Herein, the plasmonic semiconductor Cu_2-xTe disks grown on Au nanoparticles (disk-on-dot) were explored as efficient photoelectrocatalysts for hydrogen evolution reactions (HER). This has been successfully designed by growing Cu_2-xTe disks on presynthesized Au nanoparticles under optimized reaction conditions. The resulting heterostructured nanocrystals acted as efficient photoelectrocatalysts for the H₂ evolution reaction with a low Tafel slope and less cathodic overpotential in the presence of light. Details of their synthesis, characterization, optical properties, and electrocatalytic activities are studied and reported in this letter.

A multifunctional nano-therapeutic platform based on octahedral yolk-shell Au NR@CuS: Photothermal/photodynamic and targeted drug delivery tri-combined therapy for rheumatoid arthritis

Rheumatoid arthritis (RA) is a common chronic autoimmune disease that results from synovial hyperplasia. The hyperplasia of synovium directly degrades cartilage by secreting matrix-degrading enzymes and inducing cartilage degradation and even loss of joint function. In this study, a metal/semiconductor composite, octahedral copper sulfide shell, and gold nanorod core (Au NR@CuS) is designed for, photothermal therapy (PTT), photodynamic therapy (PDT), and chemotherapy (CT) combination therapy for RA to remove hyperplasia of the synovium. Upon laser irradiation, the coupling of the local surface electromagnetic field improves the electromagnetic field of the Au NR core and the absorption of light of the CuS shell, whereby the photothermal effect is enhanced. Due to the Fenton-like reactions and the integration of Au NR and CuS semiconductor photocatalyst inhibits hole recombination and provides a reaction site for photocatalysis, which introduces additional •OH to photodynamics therapy. In addition, the large octahedral void space in Au NR@CuS NPs can be used for loading a high quantity of drugs for chemotherapy, and modified with vasoactive intestinal peptide and hyaluronic acid (HA) formation VIP-HA-Au NR@CuS NPs to target synovial cells in RA. Under combination therapy, VIP-HA-Au NR@CuS NPs were shown to effectively inhibit the synovial cells and the edema degree of the CIA mouse was alleviated apparently. Both in vitro and in vivo studies indicate that the VIP-HA-Au NR@CuS NPs can provide a potential possibility for the treatment of RA.

Dual Plasmonic Au-Cu2-x S Nanocomposites: Design Strategies and Photothermal Properties

Coupling two different materials to create a hybrid nanostructured system is a powerful strategy for achieving synergistically enhanced properties and advanced functionalities. In the case of Au and Cu_2-x S, their combination on the nanoscale results in dual plasmonic Au-Cu_2-x S nanocomposites that exhibit intense photon absorption in both the visible and the near-infrared spectral ranges. Their strong light-absorbing properties translate to superior photothermal transduction efficiency, making them attractive in photothermal-based applications. There are several nanostructure configurations that are possible for the Au-Cu_2-x S system, and the successful fabrication of a particular architecture often requires a carefully planned synthetic strategy. In this Minireview, the different synthetic approaches that can be employed to produce rationally designed Au-Cu_2-x S nanocomposites are presented, with a focus on the experimental protocols that can lead to heterodimer, core-shell, reverse core-shell, and yolk-shell configurations. The photothermal behavior of these materials is also discussed, providing a glimpse of their potential use as photothermally active agents in therapeutic and theranostic applications.

Gold nanodot assembly within a cobalt chalcogenide nanoshell: Promotion of electrocatalytic activity

The assembly of functional nanoparticles within materials with unique architectures can improve the interfacial surfaces, defects, and active sites, which are key factors for the designing novel nanocatalysts. Nano metal-organic framework (NMOF) can be employed to fabricate nanodots-confined nanohybrids for use in electrocatalytic processes. Herein, we report a controlled synthesis of gold nanodot assembly within cobalt chalcogenide nanoshell (dots-in-shell Au/Co_xS_y nanohybrids). A cobalt-based NMOF (the cobalt-based zeolite imidazole framework, ZIF-67) is used as a versatile sacrificial template to yield dots-in-shell Au/Co_xS_y nanohybrids. Due to the synergistic effect of the well-dispersed Au nanodots and the thin Co_xS_y nanoshell, the obtained dots-in-shell Au/Co_xS_y nanohybrids exhibit enhanced performance for the oxygen evolution reaction (OER) with low overpotential values at a current density of 10 mA cm^-2 and a small Tafel slope (343 mV and 62 mV dec^-1, respectively).

Upconversion nanoparticles modified by Cu2S for photothermal therapy along with real-time optical thermometry

Highly effective photothermal conversion performance coupled with high resolution temperature detection in real time is urgently needed for photothermal therapy (PTT). Herein, ultra-small Cu₂S nanoparticles (NPs) were designed to absorb on the surface of NaScF₄: Yb³⁺/Er³⁺/Mn²⁺@NaScF₄@SiO₂ NPs to form a central-satellite system, in which the Cu₂S NPs play the role of providing significant light-to-heat conversion ability and the Er³⁺ ions in the NaScF₄: Yb³⁺/Er³⁺/Mn²⁺ cores act as a thermometric probe based on the fluorescence intensity ratio (FIR) technology operating in the biological windows. A wavelength of 915 nm is used instead of the conventional 980 nm excitation wavelength to eliminate the laser induced overheating effect for the bio-tissues, by which Yb³⁺ can also be effectively excited. The temperature resolution of the FIR-based optical thermometer is determined to be better than 0.08 K over the biophysical temperature range with a minimal value of 0.06 K at 298 K, perfectly satisfying the requirements of biomedicine. Under the radiation of 915 nm light, the Cu₂S NPs exhibit remarkable light-to-heat conversion capacity, which is proved by photothermal ablation testing of E. coli. The results reveal the enormous potential of the present NPs for PTT integrated with real-time temperature sensing with high resolution.

Crystal engineering of nanomaterials: current insights and prospects

Nanocrystal engineering has evolved into a dynamic research area over the past few decades but is not properly defined. Here, we present select examples to highlight the diverse aspects of crystal engineering applied on inorganic nanomaterials.

Recent Advances in the Design and Photocatalytic Enhanced Performance of Gold Plasmonic Nanostructures Decorated with Non-Titania Based Semiconductor Hetero-Nanoarchitectures

Plasmonic photocatalysts combining metallic nanoparticles and semiconductors have been aimed as versatile alternatives to drive light-assisted catalytic chemical reactions beyond the ultraviolet (UV) regions, and overcome one of the major drawbacks of the most exploited photocatalysts (TiO2 or ZnO). The strong size and morphology dependence of metallic nanostructures to tune their visible to near-infrared (vis-NIR) light harvesting capabilities has been combined with the design of a wide variety of architectures for the semiconductor supports to promote the selective activity of specific crystallographic facets. The search for efficient heterojunctions has been subjected to numerous studies, especially those involving gold nanostructures and titania semiconductors. In the present review, we paid special attention to the most recent advances in the design of gold-semiconductor hetero-nanostructures including emerging metal oxides such as cerium oxide or copper oxide (CeO2 or Cu2O) or metal chalcogenides such as copper sulfide or cadmium sulfides (CuS or CdS). These alternative hybrid materials were thoroughly built in past years to target research fields of strong impact, such as solar energy conversion, water splitting, environmental chemistry, or nanomedicine. Herein, we evaluate the influence of tuning the morphologies of the plasmonic gold nanostructures or the semiconductor interacting structures, and how these variations in geometry, either individual or combined, have a significant influence on the final photocatalytic performance.