Core-shell Nanostructures Research Articles

Bio-functionalized nanocolloids of ZnS quantum dot/amine-rich polypeptides for bioimaging cancer cells with antibacterial activity: "seeing is believing".

Among almost 200 types of cancers, glioma is considered one of the most common forms of malignant tumors located in the central nervous system (CNS). Glioblastoma (GBM), one of the deadliest types of brain cancer, remains one of the challenges faced by oncologists. Thus, smartly designed nanomaterials biofunctionalized with polypeptides can offer disruptive strategies relying on the earliest possible diagnosis ("seeing is believing") combined with more efficient therapies for fighting cancer cells. To worsen this scenario, bacteria infections very often pose a serious challenge to cancer-immunodeficient patients under chemotherapy. Thus, in this research, we report for the first time the design and synthesis of novel nanoconjugates composed of photoluminescent ZnS quantum dots (ZnS QDs), which were directly surface biofunctionalized with epsilon-poly-l-lysine (εPL), acting as an amine-rich cell-penetrating peptide (CPP) and antimicrobial peptide agent (AMP). These nanoconjugates (named ZnS@CPP-AMP) were produced through a one-step facile, eco-friendly, and biocompatible colloidal aqueous process to be applied as a proof of concept as nanoprobes for bioimaging GBM cancer cells (U87-MG) associated with synergic antibacterial activity. They were characterized regarding their physicochemical and optical properties associated with the biological activity. The results demonstrated that chemically stable aqueous colloidal nanoconjugates were effectively formed, resembling core-shell (inorganic, ZnS, organic, εPL) nanostructures with positively surface-charged features due to the cationic nature of the amine-rich polypeptide. More importantly, they demonstrated photoluminescent activity, cytocompatibility in vitro, and no significant intracellular reactive oxygen species (ROS) generation. These ZnS@CPP-AMP nanocolloids behaved as fluorescent nanoprobes for bioimaging GBM cancer cells, where the polycationic nature of the εPL biomolecule may have enhanced the cellular uptake. Additionally, they displayed mild antibacterial growth inhibition due to electrostatic interactions with bacterial membranes. Thus, it can be envisioned that these novel photoluminescent colloidal nanoconjugates offer novel nanoplatforms that can be specifically targeted with biomolecules for bioimaging to diagnose highly lethal cancers, such as GBM, and as an adjuvant in antibacterial therapy.

Developing Core-Shell Nano-Structures in FeCrAl-ODS Ferritic Alloys with the Co-Addition of Ni and Zr

Developing Core-Shell Nano-Structures in FeCrAl-ODS Ferritic Alloys with the Co-Addition of Ni and Zr

Rearranging fluorescence‐magneto spatiality for “win‐win” dual functions to enhance point‐of‐care diagnosis

AbstractFluorescent‐magneto nanoemitters have gained considerable attention for their applications in mechanical controlling‐assisted optical signaling. However, the incompatibility between magnetic and fluorescent components often leads to functional limitations in traditional magneto@fluorescence nanostructure. Herein, we introduce a new compact‐discrete spatial arrangement on a “fluorescence@magneto” core–shell nanostructure consisting of a close‐packed aggregation‐induced emission luminogen (AIEgen) core and a discrete magnetic shell. This structural design effectively eliminates the optical and magnetic interferences between the dual components by facilitating AIEgens loading in core region and reducing the magnetic feeding amount through effective exposure of the magnetic units. Thereby, the resulting magneto‐AIEgen nanoparticle (MANP) demonstrates “win‐win” performances: (i) high fluorescent intensity contributed by AIEgens stacking‐enhanced photoluminescence and reduced photons loss from the meager magnetic shell; (ii) marked magnetic activity due to magneto extraposition‐minimized magnetic shielding. Accordingly, the dual functions‐retained MANP provides a proof of concept for construction of an immunochromatographic sensing platform, where it enables bright fluorescent labeling after magnetically enriching and separating procalcitonin and lipoarabinomannan in clinical human serum and urine, respectively, for the clinical diagnosis of bacterial infections‐caused inflammation and tuberculosis. This study not only inspires the rational design of magnetic‐fluorescent nanoemitter but also highlights promising potential in magneto‐assisted point‐of‐care test and biomedicine applications.

Achieving thermochromic upconversion of Tm3+ for high-sensitive nanoprobe and information encryption

Upconversion-based optical thermometry has many merits, such as quick temperature response, higher thermal sensitivity and robust reliability. However, the previous works were mainly focused on the thermally coupled emissions, limiting their thermal sensitivity due to the intrinsic constraint by small energy gaps (e.g., <2000 cm−1) according to Boltzmann distribution theory. Here, we report a design of NaYF4:Yb3+/Tm3+@NaYF4 core-shell nanostructure to achieve thermochromic upconversion and high thermal sensitivity by taking advantage of nonthermally coupled upconversion emissions of Tm3+. We show that the blue upconversion emission of Tm3+ at 475 nm (1G4→3H6) exhibits a regular decrease with elevating temperature, while its deep-red emission at 696 nm (3F2,3→3H6) presents an increase. Such a feature leads to a rapid rise of luminescence intensity ratio (I696 nm/I475 nm) and the optimal relative sensitivity (Sr) reaches 2.79 % K−1 (503 K). More interestingly, the sample gives rise to a gradual emission color change from blue to purplish-red with lifting temperature. Our results offer a new class of upconversion-based nonoprobe with high thermal sensitivity and observable emission color variation, showing a great potential for nanoprobe and information security.

From Multi- to Single-Hollow Trimetallic Nanocrystals by Ultrafast Heating.

Metal nanocrystals (NCs) display unique physicochemical features that are highly dependent on nanoparticle dimensions, anisotropy, structure, and composition. The development of synthesis methodologies that allow us to tune such parameters finely emerges as crucial for the application of metal NCs in catalysis, optical materials, or biomedicine. Here, we describe a synthetic methodology to fabricate hollow multimetallic heterostructures using a combination of seed-mediated growth routes and femtosecond-pulsed laser irradiation. The envisaged methodology relies on the coreduction of Ag and Pd ions on gold nanorods (Au NRs) to form Au@PdAg core-shell nanostructures containing small cavities at the Au-PdAg interface. The excitation of Au@PdAg NRs with low fluence femtosecond pulses was employed to induce the coalescence and growth of large cavities, forming multihollow anisotropic Au@PdAg nanostructures. Moreover, single-hollow alloy AuPdAg could be achieved in high yield by increasing the irradiation energy. Advanced electron microscopy techniques, energy-dispersive X-ray spectroscopy (EDX) tomography, X-ray absorption near-edge structure (XANES) spectroscopy, and finite differences in the time domain (FDTD) simulations allowed us to characterize the morphology, structure, and elemental distribution of the irradiated NCs in detail. The ability of the reported synthesis route to fabricate multimetallic NCs with unprecedented hollow nanostructures offers attractive prospects for the fabrication of tailored high-entropy alloy nanoparticles.

Nanoparticle-assisted biohydrogen production from pretreated food industry wastewater sludge: Microbial community shifts in batch and continuous processes

Biohydrogen production from industrial waste has gained a significant attention as a sustainable energy source. In this study, the enrichment of biohydrogen production from pretreated dissolved air flotation (DAF) sludge, generated from food industry wastewater treatment plants, was investigated using SiO2@Cu-Ag dendrites core–shell nanostructure (NS). The effect of NS on the changes of the microbial community and biohydrogen yield was evaluated through batch and continuous tests. In batch mode, various nanomaterial doses were investigated with several concentrations ranging from 20 to 50 mg/L for hydrogen production using glucose as a substrate. The optimum core–shell NS amount was 40 mg/L, achieving a maximum H2 yield of 163 mL/g volatile solids (VS) compared to the control's 79 mL/g VS. However, 50 mg/L NS inhibited most bacteria in the sludge. The continuous experiment used a continuous stirring tank reactor (CSTR) with 40 mg/L SiO2@Cu-Ag core–shell NS and pretreated industrial sludge as substrate. The H2 yield increased to 115 L/kg VS compared to the control reactor's 89 L/kg VS. The gas analysis showed compositional proportions of 83 % H2, 7 % CO2, and 4.5 % methane, while the microbial community analysis indicated the development of hydrogen-producing species such as Clostridium. In conclusion, SiO2@Cu-Ag core–shell NS addition enhanced anaerobic degradation of organic matter and its conversion to biohydrogen. The selected nanomaterial can be used for an effective continuous treatment system for industrial sludge while promoting dark fermentation.

Synthesis and characterization of chitosan hybridized zinc phosphate/hydroxyapatite core shell nanostructure and its potentiality as delivery system of oxaliplatin drug

An advanced form of zinc phosphate/hydroxyapatite nanorods with a core-shell structure (ZPh/HPANRs) was made and then hybridized with chitosan polymeric chains to make a safe biocomposite (CH@ZPh/HPANRs) that improves the delivery structure of traditional oxaliplatin (OXPN) chemotherapy during the treatment of colorectal cancer cells. The qualifications of CH@ZPh/HPANRs in comparison with ZPh/HPANRs as a carrier for OXPN were followed based on loading, release, and cytotoxicity. CH@ZPh/HPANRs composite exhibits a notably higher OXPN loading capacity (321.75 mg/g) than ZPh/HPANRs (127.2 mg/g). The OXPN encapsulation processes into CH@ZPh/HPANRs display the isotherm behavior of the Langmuir model (R2 = 0.99) and the kinetic assumptions of pseudo-first-order kinetics (R2 > 0.89). The steric studies reflect a strong increment in the quantities of the free sites after the chitosan hybridization steps (Nm = 34.6 mg/g) as compared to pure ZPh/HPANRs (Nm = 18.7 mg/g). Also, the capacity of each site was enhanced to be loaded by 10 OXPN molecules (n = 9.3) in a vertical orientation. The OXPN loading energy into CH@ZPh/HPANRs (<40 KJ/mol) reflects physical loading reactions involving van der Waals forces and hydrogen bonding. The OXPN release profiles of CH@ZPh/HPANRs exhibit slow and controlled properties for about 140 h at pH 7.4 and 80 h at pH 5.5. The release kinetics and diffusion exponent (>0.45) signify non-Fickian transport and a complex erosion/diffusion release mechanism. The free CH@ZPh/HPANRs particles display a considerable cytotoxic effect on the HCT-116 cancer cells (9.53 % cell viability), and their OXPN-loaded product shows a strong cytotoxic effect (1.83 % cell viability).

Self-supporting hierarchical Co3O4-nanowires@NiO-nanosheets core-shell nanostructure on carbon foam to form efficient bifunctional electrocatalyst for overall water splitting

Designing cost-effective and robust bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desired in hydrogen production from overall water splitting, but still suffers great challenges due to the sluggish catalytic OER/HER kinetics. In this paper, a surface/defect engineering strategy is developed to synthesize three-dimensional (3D) carbon foam (CF)-supported unique hierarchical Co3O4 nanowires@NiO nanosheets core–shell nanostructured catalyst (NiO@Co3O4/CF) with rich oxygen-vacancies as a novel bifunctional catalyst for alkaline water splitting electrolysis. Benefited from the synergy of the 3D hierarchical core–shell structure and rich oxygen vacancies, the as-obtained NiO@Co3O4/CF shows both excellent OER (η200 = 325 mV, η500 = 374 mV) and HER (η10 = 104 mV) activities with low Tafel slopes (64.26 mV dec−1 for OER and 109.14 mV dec−1 for HER, respectively) and outstanding stability. A simple overall water splitting electrolysis cell assembled by this bifunctional NiO@Co3O4/CF as both OER and HER catalysts requires only a cell voltage of 1.53 V to obtain the current density of 10 mA cm−2 and displays a long-term stability. This work has successfully developed an approach for rational design and novel synthesis of metal oxide hybrids as bifunctional electrocatalysts with high activity and stability for overall water splitting.

Design of Silica@Au Hybrid Nanostars for Enhanced SERS and Photothermal Effect.

Core-shell nanostructures of silicon oxide@noble metal have drawn a lot of interest due to their distinctive characteristics and minimal toxicity with remarkable biocompatibility. Due to the unique property of localized surface plasmon resonance (LSPR), plasmonic nanoparticles are being used as surface-enhanced Raman scattering (SERS) based detection of pollutants and photothermal (PT) agents in cancer therapy. Herein, we demonstrate the synthesis of multifunctional silica core - Au nanostars shell (SiO2 @Au NSs) nanostructures using surfactant free aqueous phase method. The SERS performance of the as-synthesized anisotropic core-shell NSs was examined using Rhodamine B (RhB) dye as a Raman probe and resulted in strong enhancement factor of 1.37×106 . Furthermore, SiO2 @Au NSs were also employed for PT killing of breast cancer cells and they exhibited a concentration-dependent increase in the photothermal effect. The SiO2 @Au NSs show remarkable photothermal conversion efficiency of up to 72 % which is unprecedented. As an outcome, our synthesized NIR active SiO2 @Au NSs are of pivotal importance to have their dual applications in SERS enhancement and PT effect.

Rational construction of hollow ZnO@SnS2 core-shell nanorods: A way to boost catalytic removal of Cr (VI) ions, antibiotic and industrial dyes

Herein, the novel hollow ZnO@SnS2 core-shell nanorods with variable shell thickness have been synthesized by a chemical synthesis approach. The transmission electron microscopy (TEM) images signified the creation of a hollow core-shell nanostructure. The SnS2 layer coating on ZnO nanorods broadens visible light absorption and suppresses near-band edge emission of ZnO nanorods. Interestingly, the band gap (optical) of the developed ZnO nanorods decreased from 3.3 eV to 2.1 eV after the coating of SnS2 shell. Consequently, the coated hollow ZnO@SnS2 core-shell nanorods displayed a significant enhancement in catalytic activity for the decomposition of toxic industrial dyes, pharmaceutical pollutant tetracycline, and Cr(VI) ion in comparison to hollow ZnO NRs. The photon-induced charge carrier generation and separation were confirmed by the three-electrode electrochemical amperometric analysis and impedance analysis under illumination of simulated solar light (AM 1.5, One Sun). Moreover, an exceptionally higher photocurrent generation (∼10 times higher than ZnO nanorod). The improved ZnO@SnS2 core shell NRs catalytic activity was attributed to its core-shell structure, proper band structure, and effective charge carrier transfer across the core shell interface. This work offers new insights for the design and growth of visible light-active core shell nanorods for resolving environmental pollution and photocurrent generation.

Nanoengineering Liquid Metal Core–Shell Nanostructures

AbstractNanoengineering the composition and morphology of functional nanoparticles endows them to perform multiple tasks and functions. An intriguing strategy for creating multifunctional nanomaterials involves the construction of core–shell nanostructures, which have enabled promising applications in biomedicine, energy, sensing, and catalysis. Here, a straightforward nanoengineering approach is presented utilizing liquid metal nanoparticles and galvanic replacement to create diverse core–shell nanostructures. Controlled nanostructures including liquid metal core‐gold nanoparticle shell (LM@Au), gold nanoparticle core‐gallium oxide shell (Au@Ga oxide), and hollow Ga oxide nanoparticles are successfully fabricated. Remarkably, these investigations reveal that LM@Au exhibits exceptional photothermal performance, achieving an impressive conversion efficiency of 65.9%, which is five times that of gold nanoparticles. By leveraging the high photothermal conversion efficiency and excellent biocompatibility of LM@Au, its promising application in hyperthermia cancer therapy is demonstrated. This simple yet powerful nanoengineering strategy opens new avenues for the controlled synthesis of complex core–shell nanostructures, advancing various fields beyond biomedicine.

Achieving atomically ordered GaN/AlN quantum heterostructures: The role of surface polarity.

Interface engineering in heterostructures at the atomic scale has been a central research focus of nanoscale and quantum material science. Despite its paramount importance, the achievement of atomically ordered heterointerfaces has been severely limited by the strong diffusive feature of interfacial atoms in heterostructures. In this work, we first report a strong dependence of interfacial diffusion on the surface polarity. Near-perfect quantum interfaces can be readily synthesized on the semipolar plane instead of the conventional c-plane of GaN/AlN heterostructures. The chemical bonding configurations on the semipolar plane can significantly suppress the cation substitution process as evidenced by first-principles calculations, which leads to an atomically sharp interface. Moreover, the surface polarity of GaN/AlN can be readily controlled by varying the strain relaxation process in core-shell nanostructures. The obtained extremely confined, interdiffusion-free ultrathin GaN quantum wells exhibit a high internal quantum efficiency of ~75%. Deep ultraviolet light-emitting diodes are fabricated utilizing a scalable and robust method and the electroluminescence emission is nearly free of the quantum-confined Stark effect, which is significant for ultrastable device operation. The presented work shows a vital path for achieving atomically ordered quantum heterostructures for III-nitrides as well as other polar materials such as III-arsenides, perovskites, etc.

Engineering Cf /ZrB2 -SiC-Y2 O3 for Thermal Structures of Hypersonic Vehicles with Excellent Long-Term Ultrahigh Temperature Ablation Resistance.

Ultrahigh temperature ceramic matrix composites (UHTCMCs) are critical for the development of high Mach reusable hypersonic vehicles. Although various materials are utilized as the thermal components of hypersonic vehicles, it is still challenging to meet the ultrahigh temperature ablation-resistant and reusability. Herein, the Y2 O3 reinforced Cf /ZrB2 -SiC composites are designed, which demonstrates near-zero damage under long-term ablation at temperatures up to 2500 °C for ten cycles. Notably, the linear ablation rate of the composites (0.33 µms-1 ) is over 24 times better than that of the conventional Cf /C-ZrC at 2500 °C (8.0 µms-1 ). Moreover, the long-term multi-cycle ablation mechanisms of the composites are investigated with the assistance of DFT calculations. Especially, the size effect and the content of the Zr-based crystals in the oxide layer fundamentally affect the stability of the oxide layer and the ablation properties. The ideal component and structure of the oxide layer for multi-cycle ablation condition are put forward, which can be obtained by controlling the Y2 O3 /ZrB2 mole ratio and establishing Y-Si-O - t-Zr0.9 Y0.1 O1.95 core-shell nano structure. This work proposes a new strategy for improving the long-term multi-cycle ablation resistance of UHTCMCs.

Two–step pulsed laser ablation for preparation NiO@ZnO core-shell nanostructure and evaluation of their antibacterial activity

The excessive use of antibiotics led to the appearance of many strains of resistant bacteria, so it became necessary to use new antibacterial techniques. The aim of this work is the synthesis of novel core–shell NPs (NiO@ZnO) for antibacterial applications. A novel NiO@ZnO core–shell nanomaterial with a nanosize and uniform shape has been synthesised using the two-step pulsed laser ablation in liquid (PLAL) method. The first step is the laser ablation of the nickel target and the production of NiO NPs (core) colloidal, followed by the second step, the ablation of ZnO (shell) inside NiO NPs colloidal. The transmission electron microscopy results approve the formation of NiO@ZnO core–shell NPs with an average particle size of 54.4 nm for NiO particles and 60.7 nm for the NiO@ZnO core–shell. The antibacterial activity was examined against the pathogenic bacterial strains E. coli and S. aureus. We found that in the case of NiO, the inhibition rates were 62.4 and 59.2% for E. coli and S. aureus, respectively. While with NiO@ZnO NPs, this result was improved to 74.8% for E. coli and 71.2% for S. aureus. So, it was found that using the core–shell NPs increased the antibacterial activity of NPs, and the use of NiO NPs and core approved their effect as antibacterial agents due to their special properties. This behaviour is primarily because of the accumulation of the NiO@ZnO NPs on the surface of the bacteria, which leads to cytotoxic bacteria and a relatively increased ZnO, causing cell death. Furthermore, the use of a NiO@ZnO core–shell material will inhibit the bacteria from nourishing themselves on the culture medium. Therefore, core shelling metal oxides with another metal oxide or other material improves their antibacterial activity compared with using them alone.

Defects engineering of Au@MoS2 nanostructures for conventional and plasmon-enhanced hydrogen evolution reaction

The influence of thermal treatment under reducing conditions on the structural and hydrogen evolution reaction (HER) properties of Au@MoS2 structures is reported in this work. After a thermal treatment at 800 °C under H2 atmosphere, the Au@MoS2 nanostructures exhibit remarkable performance with an overpotential of 203 mV vs reversible hydrogen electrode (RHE) at 10 mA/cm2 and a Tafel slope of 55 mV/dec which is similar to the value reported for edges sites in MoS2. The samples were investigated by combining ex-situ and in-situ aberration-corrected transmission electron microscopy (TEM) experiments under controlled atmosphere, Raman and XPS spectroscopies. (S) TEM characterization highlights the formation of the core-shell system as well as the decrease of the number of shell layers up to incomplete layers induced by the thermal treatments. The plasmonic-assisted HER performances of these nanostructures under LED illumination are also explored and an enhancement by about 10 % of the current density, depending on the wavelength used, is also reported. These results open new avenues for the design of core shell nanostructures based on transition metal dichalcogenides for the hydrogen evolution reaction.

High-sensitive nonthermally coupled upconversion for ultralow temperature sensing

Upconversion based nanothermometry has received much attention due to its merits of stability, narrow band emission and rich emission peaks. However, the previous works are mainly focused on the emissions from thermally coupled energy levels which is theoretically limited by Boltzmann distribution theory with resultant low temperature sensitivity in particular at ultralow temperatures. Here we report a LiYF4:Yb/Ho@LiYF4 core-shell nanostructure to improve the sensitivity at low temperatures by taking advantage of non-thermally coupled energy levels of Ho3+. In detail, the green upconversion emission of Ho3+ shows an increase with reducing temperature while its red upconversion emission presents a decline during the same process. This is primarily due to the suppression of the non-radiative multi-phonon relaxation occurred at the green emitting levels (5F4,5S2) and the intermediate level (5I6) at low temperatures. Such a feature contributes to a high relative sensitivity of 7.17%/K at 11 K, much higher than reported values. Our results provide a promising candidate for the development of nanothermometer with high-sensitive low-temperature sensing performance.

Target-triggered cascade signal amplification in nanochannels: An ingenious strategy for ultrasensitive photoelectrochemical DNA bioanalysis

Artificial solid-state nanochannels have aroused intense interests in biosensors and bioelectronics because of their special architectures. Herein, we pioneered an ingenious approach of target-triggered cascade signal amplification in porous anodic aluminum oxide (AAO) nanochannels for ultrasensitive photoelectrochemical (PEC) DNA bioanalysis. In the design, AAO nanochannels were modified initially with capture DNA (cDNA) and then incorporated with a photoelectrode, yielding the desired architecture of highly ordered nanoarrays on top of the signal transducer. For target DNA (tDNA) probing, exonuclease III (Exo-III) mediated target recycling (ETR) was first activated to generate plenty of output DNA (oDNA) fragments. After oDNA and the conjugate of Au-labeled probe DNA (Au-pDNA) were anchored within the nanochannels via DNA hybridization, in-situ synthesis of Ag shells on tethered Au nanoparticles was conducted. The resulting large-sized Au@Ag core-shell nanostructure within the nanochannels would cause conspicuous blocking effect to hinder the transportation of electrons accessing the photoelectrode. Since the signal inhibition was directly related to tDNA concentration, an innovative nanochannels PEC DNA assay was exploited and qualified for ultrasensitive detection. The anti-interference ability of this platform was also emphasized by the split AAO membrane for biological incubation without participation of the photoelectrode. This featured nanochannels PEC strategy with cascade amplification launched a novel detecting platform for trace levels of DNA, and it could spark more inspiration for a follow-up exploration of other smart nanochannels PEC bioassays.

Parametric Study of the Galvanic Reaction Parameters on the Synthesis of 1-Dimensional Cu-Ag Nanostructures

Recently, copper (Cu) and silver (Ag) nanowires have been widely employed as conductive fillers in flexible electronic devices due to their high aspect ratios leading to the formation of conductive networks in a polymeric substrate. This study combined Cu and Ag as a 1-dimensional nanostructures through galvanic replacement with a core-shell configuration. The effects of the galvanic replacement factors on the Cu-Ag core-shell nanostructures morphology was studied by varying the reaction time, temperature, and Ag concentration. SEM images show a more extensive Cu dealloying and Kirkendall voiding with longer reaction times, resulting in the Cu core dissolution. Homogenous nucleation of Ag occurs at higher reaction temperatures and Ag concentrations, producing separate Ag particles.

Decentralized core-shell Au/Ag bimetallic nanostructures prepared via green approach for catalytic and antimicrobial applications

Synthesis of noble metallic nanomaterials via green routes using various plant extracts has witnessed a remarkable rise in applications and research interest over the past decade. These biogenic routes are devoid of toxic chemicals, harsh preparation environments, and external capping agents, coupled with their cost-effectiveness, have attracted researchers to adopt green chemistry in nanotechnology. In this study, we synthesized Au, Ag, and Au/Ag nanoparticles (NPs) using a facile method employing an extract derived from a mixture of spices. Optical, morphological, and structural analysis is carried out using UV-visible spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX), Fourier- transform infrared spectroscopy (FTIR), and X-ray diffraction studies (XRD), respectively. The Zeta potential of the prepared NPs was determined using dynamic light scattering spectroscopy (DLS). Optimization of pH to 10 and 8 was performed for the synthesis of Ag and Au NPs, respectively, crucial for precise tuning of their optical absorption spectra. Finite difference time domain (FDTD) simulations validate the experimental findings. The Ag NPs exhibit primarily uniform and spherical size and shape, whereas the Au NPs display a variety of shapes including spheres, rods, and triangular plates. This variation is attributed to the influence of pH and concentration of precursors. TEM analysis confirmed the formation of Au/Ag bimetallic core-shell nanostructures (NSs), characterized by a decentralized gold core. XRD confirmed the formation of FCC crystallites. FTIR spectra identified the possible biological functional groups responsible for reduction and capping. Furthermore, a negative zeta potential exceeding 20 mV confirmed the stable formation of NPs. These NPs were capped by negatively charged functional groups, thereby avoiding agglomeration. Both mono and bimetallic NSs exhibited enhanced catalytic activity for reducing 4-nitrophenol in the presence of sodium borohydride (NaBH4). Furthermore, Ag and Au/Ag NPs have exhibited antibacterial properties against specific bacteria, which are discussed in detail.

Core-shell ZnO/BiOBr p-n heterojunction with excellent photocatalytic performance in degradation of tetracycline hydrochloride

Core-shell ZnO/BiOBr heterojunction was prepared by a simple hydrothermal-ionic liquid method. Hollow ZnO microspheres were firstly synthesized by hydrothermal method. Then BiOBr nanosheets were evenly wrapped on the ZnO microspheres through an ionic-liquid method. The prepared dahlia-like core-shell ZnO/BiOBr microspheres had a much larger BET surface area and mesopore volume than that of ZnO. Its visible-light absorption and charge carrier's separation were greatly enhanced due to the synergistic effect of the core-shell nanostructure and formation of ZnO/BiOBr heterojunction. It had an excellent photocatalytic performance in the degradation of tetracycline hydrochloride (TC): 86.76 % TC was degraded after irradiation for 90 min., which was 1.38 times of the pure ZnO and 1.35 times of the BiOBr, respectively.