Microwave-assisted Approach Research Articles

Structure-based design and synthesis of (E)-l-(s-pheny1)-N-(4-(2,2,4-trimethy1-2,3-dihydro-lH-benzo[b][l,4]diazepin-l-yl)phenyl)methanimine motifs as antimicrobial and anti-tubercular agents

Benzodiazepines' chemistry and synthesis as heterocyclic compounds have recently attracted a lot of attention, due to their extensive biological diversity in drug design and potential for usage in agrochemicals. Eco-friendly and highly efficient method was herein reported for the synthesis of a new series of Schiff base of benzodiazepine derivatives 3a-l using microwave-assisted approach. Firstly, 2,2,4-trimethy1-2,3-dihydro-lH-benzo[b][l,4]diazepine (1) was synthesized by AgNO3-catalyzed reaction of o-phenylenediamine with excess of acetone. Coupling of benzodiazepine 1 with 4-chloroaniline afforded intermediate benzodiazepine 2 which was subsequently reacted with benzaldehyde derivatives via microwave irradiation technique to access twelve final targeted benzodiazepine Schiff bases, 3a-l. The chemical structures of the scaffolds 3a-l were authenticated using analytical and spectroscopic data. Benzodiazepine Schiff bases 3a-l were investigated for their in vitro antimicrobial activities using Agar diffusion technique and screened for their minimum inhibitory concentration (MIC) using microtube dilution technique. Ten pathogenic organisms comprising of seven bacterial and three fungal isolates were utilized for the screening. Ciprofloxacin was the positive control for antibacterial screening while fluconazole was engaged as the positive control for the antifungal screening. The most efficacious antimicrobial agent among the series was (E)-l-(2-Chloropheny1)-N-(4-(2,2,4-trimethyl-2,3-dihydro-lH-benzo[b][l,4] diazepinlyl)phenyl)methanimi ne (3b) with a MIC value of 3.13 µg/mL and MBC of 6.25 µg/mL among all the synthesized compounds synthesized and screening for antimicrobial assessment. Compound 3b also emerged as the best anti-tubercular agent IC50 of 40 µg/mL against Mycobacterium tuberculosis, Mycobacterium bovis and H37Rv

Ultra-sensitive liquefied petroleum gas (LPG) sensor based on monometallic Ag nanospheres synthesized via microwave-assisted facile approach

We present the synthesis, analysis, and utility of polyvinylpyrrolidone (PVP) stabilized monometallic silver nanospheres for liquefied petroleum gas sensing at room temperature. We have synthesised silver nanospheres (Ag-NSs) in the diameter range of 13–21 nm using a microwave assisted method, which is both easy and fast, because microwave irradiation only takes 30 s. A solution of 0.1 M silver nitrate (AgNO3) in an ethanolic medium was microwave-irradiated to produce Ag-NSs. PVP was used as a stabilising agent throughout the process. Spin coating method was used to produce thin films of synthesised monometallic Ag-NSs. X-ray diffraction (XRD), scanning electron microscopy (SEM), acoustic particle sizer (APS), UV–visible absorption (UV–visible) and Fourier Transform Infrared (FT-IR) spectroscopy were used for characterising Ag-NSs. Based on the acoustic attenuation of the prepared sample, the acoustic particle sizer estimated the diameter of Ag-NSs to be around 17 nm. The deposited films were examined for LPG leakage detection at ambient temperature. This is the first report on monometallic Ag-NSs for leakage detection of LPG at room temperature operation below its lower explosive limit (LEL). The significant finding of the developed sensor is that it prompts the quick response (∼16 s) and recovery (∼64 s) as Ag enhances the reaction rate between the sensing film surface and adsorbed LPG, thereby, augments the sensitivity of sensor even below LEL. Moreover, the fabricated LPG sensor shows noteworthy reproducibility (measured up to six cycles) and stability up to 06 months after fabrication.

Effect of pH on the microstructure and antibacterial properties of MgO nanoparticles by microwave-assisted solution combustion

The application of magnesium oxide (MgO) nanoparticles as a candidate material for antibacterial purposes has been limited by their relatively low antibacterial activity. In this study, antibacterial MgO nanoparticles were synthesised in one step using magnesium nitrate and citric acid as raw materials using an economical and environmentally friendly microwave-assisted solution combustion approach, while the effect of the pH of the reaction system (2, 4, and 7) on the structure and antimicrobial properties of the synthesised MgO nanoparticles was investigated. X-ray diffraction (XRD) analysis demonstrated the formation of cubic-phase MgO nanoparticles, and electron microscopy studies confirmed that MgO nanoparticles synthesised at a precursor solution pH of 4 had uniform size distribution with a small microcrystalline size (∼19 nm) and spherical granular morphology. In addition, the results of the plate colony counting method showed that the antibacterial rate of MgO-4 against Gram-negative Escherichia coli (106 CFU/mL) at a sample concentration of 100 μg/mL was as high as 99.86 %, which showed excellent antibacterial performance. These findings provide valuable insights into how to increase the degree of oxygen adsorption on the sample surface to participate in the reaction, as well as a potential method for constructing nanomaterials with high antimicrobial activity.

Harnessing potential of microwave-assisted ultrafast synthesis of reduced graphene oxide/Mn3O4 bioactive nanocomposite hydrogel for bone tissue engineering

The development of functional materials with the potential for bone tissue regeneration along with rapid synthesis and cost-effective approach has been challenging. In this regard, hydrogels have been explored as a potent candidate to behave as a 3D scaffold for bone repair. However, poor mechanical attributes impeded their clinical translation. Enthralling demonstration of the potential of carbon-based nanocomposites in bone tissue engineering has been constantly encouraging the fabrication of advanced nanocomposites. Here, we investigated the fabrication of reduced graphene/manganese (II, III) oxide (RGO/Mn3O4) nanocomposites by taking advantage of the microwave-assisted synthesis approach for cost effective, and ultrafast synthesis. Mn3O4 nanoparticles with uniform distribution in RGO sheets and ∼ 1.7 nm size was fabricated using the approach. Further, fine-tuning of the structural interaction and mechanical behavior of the GelMA-based hydrogels upon reinforcement with RGO/Mn3O4 nanocomposites was investigated as a function of different concentrations of the nanocomposites where upto 50 % increment in the compressive stress was observed compared to native GelMA hydrogel. The ability of these hydrogels was further investigated for their osteogenic behaviour on MC3T3-E1 preosteoblast cells where constant cell proliferation for up to 10 days was witnessed for the hybrid hydrogel with the highest concentration of the nanofillers.

Biomass-Derived Co/MPC Nanocomposites for Effective Sensing of Hydrogen Peroxide via Electrocatalysis Reduction

Utilizing the full potential of reproducible biomass resources is crucial for the sustainable development of humanity. In this study, biochar (MPC) was prepared through the microwave-assisted pyrolysis of sugarcane bagasse. Subsequently, Co nanoparticles were introduced by microwave-assisted hydrothermal treatment to form a highly dispersive Co/MPC material. Characterization results indicated that Co nanoparticles were wrapped by thin carbon layers and uniformly dispersed on a carbon-based skeleton via a microwave-assisted hydrothermal synthesis approach, providing high-activity space. Thus, the prepared material was limited to glassy carbon; on the electrode surface, a cobalt-based sensing platform (Co/MPC/GCE) was built. On the basis of this constructed sensing platform, a linear equation was fitted by the concentration change of current signal I and H2O2. The linear range was 0.55–100.05 mM; the detection limit was 1.38 μM (S/N = 3); and the sensitivity was 103.45 μA cm−2 mM−1. In addition, the effect this sensor had on H2O2 detection of actual water samples was conducted by using a standard addition recovery method; results disclosed that the recovery rate and RSD of H2O2 in tap water samples were 94.0–97.6% and 4.1–6.5%, respectively.

Amide coupled Si-rGO hybrids as anode material for lithium-ion batteries

Despite silicon (Si) having a high specific capacity of 4200 mA h/g, it undergoes significant expansion in volume during lithiation. In order to alleviate the significant increase in volume that occurs in silicon nanoparticles (SiNPs) of lithium-ion batteries, herein we report covalently modified SiNP contained within reduced graphene oxide (rGO) sheets as an anode material in lithium-ion batteries (LIBs). The structural modification of SiNP could effectively mitigate the increase in volume while preserving its outstanding electrochemical properties. Graphene oxide (GO) undergoes chemical modification and functionalization by a simple and efficient method using microwave-assisted sonochemical approach. The procedure entails grafting carboxyl functionalized silicon nanoparticles (C-Si) to amine-functionalized reduced graphene oxide (NH2-rGO) to produce a Si-rGO hybrid via amide linkage. This hybrid reduces the problem of volume expansion in Si anodes by dissipating substantial changes in volume and minimizing direct contact between SiNPs and the electrolyte. The formation of a robust solid electrolyte interface (SEI) layer improves the specific capacity and durability of the anode material. We observed that the Si-rGO 2 hybrid (containing 44 wt% Si) exhibited a relatively higher specific capacity of 1604 mA h/g during the initial cycle at C/10 rate when compared to other hybrid systems, such as Si-rGO 1, Si-rGO 2, Si-rGO 3 with bare SiNP, and SRGO composite (without amide linkage). Additionally, it maintained a capacity of approximately 1000 mA h/g at C/2 rate for more than 125 cycles. Thus, enhanced specific capacity, cycling stability, electrode conductivity, and lithiation are made possible due to the structural modification of SiNPs.

Microwave assisted preparation of ternary scheelite CaMoO4: Er3+/Yb3+ nano-phosphors for up/down-conversion photoluminescence, temperature sensing and antibacterial properties

Due to their exceptional intrinsic optical characteristics, molybdate compounds have aroused significant attention in recent years for their effective up and downconversion luminescence. In the present study, a series of xEr3+/Yb3+ (x = 0.5 %, 1 %, 2 %, 4 % and Yb3+ =15 %) doped CaMoO4 nanophosphors synthesized through a microwave assisted approach and subsequently the comprehensive analysis of the functionalities such as optical properties, antibacterial traits and their integration with temperature sensing, have been explored. Furthermore, the structural refinement confirms the occurrence of tetragonal scheelite phase of the prepared materials. The morphology of the material was identified by FE-SEM and HR-TEM analysis which reveals particles are in spherical shape. Up-conversion luminescence intensities were found to be dependent on doping concentration, laser excitation power and external temperature upon 980 nm light excitation. The temperature sensing response of the optimized sample was examined based on intensity ratio of two emission bands that involves thermally connected energy levels of Er3+ ion. The maximum absolute sensitivity of 10.74 × 10−3 K−1 (at 500 K) was found, demonstrating its potential application in high temperature thermometry. The comprehensive analysis and the outcome of the present study suggests the potential prospect of the as-synthesized material in food preservation, medical equipment, water treatment, and as an optical coating agent for solid state luminous devices.

(Invited) Core-Multi-Shell Design: Unlocking Multimodal Capabilities in Lanthanide-Based Nanoparticles

The remarkable optomagnetic properties of the lanthanides (Ln) make Ln-based materials ideal for biomedical applications, including diagnostic (e.g., imaging, nanothermometry) and therapeutic (e.g., drug delivery, photodynamic therapy) approaches. This is due the unique electronic properties of the f-elements allowing for upconversion and near-infrared emission under near-infrared excitation as well as high magnetic moments. Yet, challenges remain, including low emission intensity and efficiency of small nanoparticles (NPs), and reliable, fast synthesis routes. As material chemists, we tackle these challenges with new designs of Ln-NPs by chemically controlled synthesis, application-oriented surface chemistry, and understanding of structure-property-relationships. We developed a straightforward and rapid microwave-assisted synthesis approach towards core-multi-shell Ln-NPs. Careful architecture design and choice of RE3+ dopant ions allow to tune the optical properties of the resultant nanoparticles, i.e., upconversion and near-infrared emission. This presentation will shed light on recent results with respect to microwave-assisted synthesis of Ln-NPs as well as structural and optomagnetic properties, seeking biomedical application.For instance, multimodal bioimaging probes merging optical imaging, magnetic resonance imaging (MRI), and X-ray computed tomography (CT) capabilities have attracted considerable attention due to their potential biomedical applications. This includes nanoparticles that combine upconverting Er3+/Yb3+ and magnetic NaDyF4 for optical/T2-weighted MRI/CT multimodal capabilities. A known drawback of multimodal probes that merge the upconverting Er3+/Yb3+ ion pair with magnetic Dy3+ ions for T2-weighted MRI is the loss of upconversion emission due to Dy3+ poisoning. The synthesis of controlled nanoparticle architectures with tuned inner NaGdF4 shell thicknesses separating Dy3+ and Er3+/Yb3+ allow to shed light on this distance-dependent loss of upconversion due to Yb3+ → Dy3+ energy transfer. As a result, the Ln-NP architecture was tuned to not only restore but enhanced the upconversion emission. In addition to multimodal imaging, Ln-NPs are promising candidates for application in nanothermometry due to the distinct, temperature-induced changes in their spectral features. We seek the development of novel Ln-NP nanothermometers for new opportunities in the near-infrared biological transparency windows (1000 to 2000 nm), by doping RE3+ ions, such as Er3+ and Tm3+ as well as unconventional Pr3+, into core-multi-shell lanthanide-based nanoparticles.

Sodium yttrium fluoride doped with Er3+ ions for thermally and non-thermally coupled nano-thermometry and IR detection applications

Microwave-assisted combustion synthesis approach was adopted to prepare sodium yttrium fluoride doped with erbium (NaYF4: Er3+) nanoparticles. Powder x-ray diffraction study confirmed the formation of mixed phase of NaY1-xF4: xEr3+ (x = 1, 3, 5, 7 and 9 mol%) sample with cubic and hexagonal phases (predominant). Three characteristic emission peaks appearing at 526, 546 and 670 nm were attributed to the transitions 2H11/2, 4S3/2 and 4F9/2 to 4I15/2 respectively which are characteristic emissions of Er3+ ions when excited with 980 nm radiation. The optimal dopant concentration was determined as 7 mol% of Er3+ ions in yellowish-green region, and the asymmetric ratio was also calculated. The synthesized up-converting sample follows two-photon process for excitation which was confirmed by power law by varying pump-power in the range of 49–143 mW. The thermally and non-thermally coupled levels attributed to the transitions (2H11/2 and 4S3/2), (2H11/2 and 4F9/2) of Er3+ ions were employed to study the temperature sensing which was recorded in 300–550 K and the relative sensitivities were evaluated to be 0.92 and 0.58 %K−1 correspondingly. The significant thermal sensitivity of the synthesized phosphor materials promises its possibility in optical thermometry applications. The synthesized sample when excited with 980 nm laser radiation produced emission in the visible region which facilitates the utilization of sample as infrared (IR) detector. In the purview of solid-state lighting, the luminous efficiency and luminous efficacy of radiation were evaluated as 23.57 % and 161 lm/Wop respectively. The optical thermometry, IR detection and light generation capabilities of the hexagonal-phased sodium yttrium fluoride doped with erbium (NYF:Er) ions are demonstrated with the obtained results.

Comparative study of microwave-assisted and hydrothermal hydroxyapatite synthesis from neutralization slag: Optimization, energy, and adsorption

The study proposes the utilization of microwave-assisted methods for converting neutralization slag (NS) into hydroxyapatite (HAP), offering an alternative to the conventional hydrothermal method. The microwave-assisted approach addresses the challenges encountered in hydrothermal reactions, such as particle agglomeration, reduced specific surface area, prolonged reaction time, high temperature requirements, and inadequate saturation adsorption capacity. By employing the response surface methodology with a Box-Behnken design, the study found that the microwave-assisted method significantly reduced the synthesis time from 90 to 25 min and the temperature from 120 °C to 56 °C. Furthermore, the microwave method consumed only 1/43 of the energy utilized in hydrothermal synthesis. To assess the performance of the synthesized HAP, various detection methods were utilized, including XRD, SEM-EDS, FTIR, Zeta potential, and ICP, which analyzed the crystal structure, crystallinity, morphology, chemical composition, and surface charge of HAP. The BET method was used to measure the specific surface area, further confirming the successful synthesis of HAP. The HAP synthesized through this microwave-assisted method exhibited a saturation adsorption capacity of up to 98.4 mg/g of fluoride ions from vanadium industrial raffinate. This study demonstrates that the microwave-assisted method provides a viable solution for reducing energy consumption and enhancing HAP synthesis efficiency for wastewater treatment in the vanadium industry.

Superior adsorptive uptake of methylene blue pollutant by nanobiochar- impregnated-layered double hydroxides

Design and assembly of novel, sustainable, ecofriendly and low-cost nanobiosorbents by facile and green approaches are generally aimed to apply in remediation of toxic and nonbiodegradable pollutants from aquatic systems. Hence, the current study is directed to synthesize a novel nanobiosorbent by a facile solid–solid and microwave-assisted approach for direct impregnation of derived nanobiochar from pomegranate peels waste feedstock (PPNC) onto magnesium (II) aluminum (III)-layered double hydroxide (MgAl-LDH) for the generation of MgAl-LDHs@PPNC. This was initially characterized by several techniques to confirm the morphological and structural features. The particle size range was identified (13.47–41.78 nm) and the concluded elemental compositions were Al (9.49 %), Mg (19.33 %), C (25.4 %), and O (45.78 %) according to the energy-dispersive X-ray (EDX) analysis. The Fourier Transform-infrared (FT-IR) study denoted to several incorporated surface functionalities as –COOH, –OH, metal–O and others functionalities. MgAl-LDHs@PPNC exhibited a good surface area 275.57 m2g−1, while the zero-charge point was also detected at 6.0. Some experimental impacting conditions were testified and optimized by the batch removal system of methylene blue dye pollutant (MBDP) by MgAl-LDHs@PPNC. The concluded optimum conditions were figured out at pH 7.0, 15 min reaction duration, 25 mg nanobiosorbent dosage and 25 °C reaction temperature. Related expressions to isotherm and kinetic investigations were testified to confirm the most correlated experimental data to both Freundlich and pseudo-2nd-order expressions. Thermodynamic parameters were additionally computed to refer to the exothermal spontaneity trends in adsorptive reaction of MBDP onto MgAl-LDHs@PPNC. The evaluated nanobiosorbent is therefore, labeled with high stability to providing highly acceptable efficiency at 82.7–99.2 % (5 mgL−1) by the first-fifth regeneration processes. MgAl-LDHs@PPNC was finally afforded excellent removal uptake of MBDP (5 mgL−1) from real contaminated waters giving 93.17–98.27 %.

ZnSe:Cu@ZnS core/shell quantum dots synthesis by photochemical method for ethanol gas sensing

In the present study, ZnSe, ZnSe:Cu and ZnSe:Cu@ZnS core/shell quantum dots (QDs) were synthesized at room temperature using the new and fast microwave-assisted photochemical approach recently reported by the authors. Gas sensors based on these QDs were made and their sensitivity was studied in response to different flows of ethanol gas. Morphology and elemental analyses (conducted via FESEM, TEM, EDS and Map) were performed alongside XRD line profile analysis using Halder-Wagner approach. TEM results showed that the synthesized QDs exhibited spherical morphology of particles with an average size of approximately 20 nm, except for ZnSe:Cu(1.5 %)@ZnS (including nanorods). Ethanol gas sensing measurements were conducted under ambient conditions. Coating the Cu (1.5 mol%)-doped cores with ZnS increased the sensitivity, while the undoped samples exhibited the opposite trend. Among the fabricated sensors, the most sensitive one was made of ZnSe without microwave irradiation (MWIR), although it lacked desired stability. Meanwhile, ZnSe:Cu(1.5 %)@ZnS nanorods were identified as the most sensitive (optimal) sample, demonstrating favorable stability. Consequently, the gas sensitivity of the optimal sample to various ethanol gas flow rates was tested. It was observed that gas sensitivity increased with increasing flow rate up to 150 ml/min and decreased somewhat at higher flow rates.

Utilization of coffee waste for biofuel production through catalytic microwave-assisted pyrolysis approach

Utilization of coffee waste for biofuel production through catalytic microwave-assisted pyrolysis approach

Electrochemical Detection of Heavy Metal Ions using Gold Nanoparticles on Carbon Dots Extracted from Curry Leaves

Carbon dots (CDs) have attracted attention due to their versatility in electronic and optical properties based on precursor and type of synthesis process. Recently, many researchers have focused on using natural resources or wastes to form CDs. Four samples of CDs have been synthesized from curry leaves using a microwave-assisted approach at heating powers of 700 and 800 V with durations of 5 and 8 minutes. UV-Vis and FTIR spectra reveal the existence of carbon graphitic elements with carboxyl and hydroxyl functional groups on the surfaces of CDs. CVs of AuNPs/CDs/GS electrodes in ferricyanide disclosed that as-synthesized CDs produced using a lower heating power of 700 W exhibit pronounced electrocatalytic activity with sluggish electron transfer kinetics. Conversely, as-synthesized CDs created with a higher heating power of 800 W demonstrate reduced electrocatalytic activity but rapid electron transfer kinetics. Electrochemical detection of Pb2+ ions was observed through a sharp peak around -0.42 to -0.438 V, while detection of Hg2+ ions was observed through two anodic peaks around +0.334 to +0.408 V during a forward scan in acetate buffer (pH 4.5) on AuNPs/CDs/GS electrodes when tested individually. These distinct peaks also appeared in mixture solutions, with a slight reduction in peak current density that suggests the selectivity of the AuNPs/CDs/GS electrodes towards Pb2+ and Hg2+ ion detection. The optimum AuNPs/CDs/GS electrode for sensitive and selective detection of Pb2+ and Hg2+ was recorded using CDs D as a functional supporting matrix for AuNPs that was synthesized using a heating power of 800 W for 8 minutes.

Revelation of luminescence-thermometry, light generation in first biological window and IR detection capabilities of sodium yttrium fluoride co-doped with Yb3+ and Er3+ ions synthesized by low-cost approach

Microwave-assisted combustion synthesis approach is adopted to prepare sodium yttrium fluoride co-doped with ytterbium and erbium (NaYF4: Er3+/ Yb3+) nanoparticles. PXRD confirms the formation of mixed phase (cubic and hexagonal) of the NaYF4: Er3+/ Yb3+ crystal lattice. It is determined that the cubic phase dominates over the hexagonal phase. Three characteristic emission peaks appearing at 523, 544 and 672 nm are attributed to the transitions 2H11/2, 4S3/2 - 4I15/2 and 4F9/2 - 4I15/2 respectively which is character of Er3+ ions, confirming the potential in first biological window applications. The optimal dopant concentration is found and the asymmetric ratio is calculated. Strong up-conversion emission has been observed in the sample in the yellowish-green area when excited with 980 nm radiation. The life time of the 4S3/2 (green) and 4F9/2 (red) levels are found to be 1.187 and 0.472 ms respectively. The emission occurring in the synthesized sample follows the two-photon process which is confirmed by double log graph of intensity and pump-power. Thermal sensitivity is recorded in the range of 300–540 K. The thermally and non-thermally coupled levels attributed to the transitions (2H11/2 and 4S3/2) to (2H11/2 and 4F9/2) of Er3+ ions which are employed to study the temperature sensing. Higher relative sensitivities in both thermally and non-thermally coupled levels were observed in the samples with their values being 1.33 % K−1 and 1.81 % K−1 correspondingly. The significant thermal sensitivity of the synthesized phosphor materials improves its possibility in optical thermometric applications. Further to study the light-emitting abilities of the prepared phosphor, a phosphor-in-glass structure was fabricated using a borate-based glass system. The photometric parameters such as luminous efficacy of radiation and luminous efficiency were obtained to be 331 lm/Wopt and 48.46 % respectively. The prepared compound exhibits superior IR sensing which is evident upon exposure of the fabricated P-i-G to 980 nm radiation. The performed studies authenticate the capabilities of the cubic phase NYF in optical thermometry, light generation and IR detection abilities.

One-pot microwave-assisted approach of polydiacetylene/zinc oxide nanocomposite for reversible thermochromic

This study introduces a new technique to fabricate the reversible poly(PCDA/ZnO) nanocomposites thermochromism. Our preparation process is the solution-mixing method, which is supported by microwave synthesis time instead of ultrasonic bath or stirrer. The presence of ethanol molecules in aqueous media in the solution-mixing method induces dipolar polarization. In addition, the presence of Zn2+ leaking out of the ZnO can produce ionic polarization. These factors affect the shape of poly(PCDA/ZnO) nanocomposites based on their thermochromic properties. The optical properties of poly(PCDA/ZnO) nanocomposite were determined through UV-Vis absorption spectroscopy. The morphology of this nanocomposite was examined by scanning electron microscopy, and its crystallinity was investigated by X-ray diffraction. The inter-intrachain interaction was confirmed by infrared spectroscopy. In addition, the poly(PCDA/ZnO) nanocomposite embedding PVA was prepared. The reversible theromochromic properties of poly(PCDA/ZnO) nanocomposites demonstrated a higher color transition temperature with increasing microwave synthesis time. It is an important observation to understand the effect of microwave synthesis time on the morphology and reversible thermochromism of the poly(PCDA/ZnO) nanocomposite

The Influence of Precursor and Seminyak (Champeria sp.) Leaf Extract Concentrations in Microwave-Assisted Silver Nanoparticle Fabrication

Abstract Silver nanoparticles (AgNPs) possess remarkable characteristics, including high antibacterial efficacy, excellent thermal conductivity, and superior electrical conductivity. However, conventional methods employed for AgNPs synthesis still rely on the use of hazardous chemicals, which pose significant threats to the environment and human health. Recently, the synthesis of AgNPs using green and sustainable methods has gained considerable attention. In this study, concentration of AgNO3 (1; 10 and 100 mM) and Seminyak (Champeria sp.) leaf extract (1 and 2 wt%) were varied to know their influence on the fabrication of AgNPs through a microwave-assisted synthesis approach. The results demonstrated that the precursor and Seminyak leaf extract concentrations significantly influenced the AgNPs properties. Visual and UV-Vis spectroscopy results suggested that AgNPs might only form at 100 mM AgNO3, which is indicated by darker appearance of sample and the presence of broad peak at 400-500 nm. Based on transmission electron microscopy (TEM) results, increasing the Seminyak leaf extract concentrations exhibited enhanced stability and monodispersity of the nanoparticles with the average particle size of 26.8 ± 10.9 nm and 17.8 ± 7.6 nm for 1 and 2 wt%, respectively. The optimized precursor and Seminyak leaf extract concentrations can be utilized to tailor the size and morphology of AgNPs, making them suitable for various applications such as catalyst, electronics, and medicine.

Novel Tb³⁺-Doped LaAl₂B₄O₁₀ phosphors: Structural analysis, luminescent properties, and energy transfer mechanism

This study explores the structural and luminescent properties of terbium (Tb³⁺)-doped lanthanum aluminium borate (LaAl₂B₄O₁₀, abbreviated as LAB) phosphors, a novel host lattice for Tb³⁺ doping. LAB:Tb³⁺ phosphors, with varying dopant concentrations, were synthesized using a microwave-assisted combustion synthesis approach and characterized using X-ray diffraction (XRD), Rietveld refinement, and photoluminescence spectroscopy at both room and low temperatures. The structural analysis confirmed the hexagonal crystal structure of LAB and revealed successful incorporation of Tb³⁺ ions without altering the fundamental lattice. Luminescence studies demonstrated that the LAB:Tb³⁺ phosphors show strong green emission primarily attributed to the 5D4→7F5 transition of Tb³⁺. The optimal doping concentration was determined to be 5 wt% Tb³⁺, which provided maximum luminescence efficiency. This concentration also allowed for a critical study of energy transfer mechanisms within the phosphor, revealing dipole-dipole interactions with a critical distance of 9.80 Å between Tb³⁺ ions. Additionally, the CIE chromaticity coordinates of LAB:0.05 Tb³⁺ were precisely determined to be (0.289, 0.4460), indicating the potential for high-quality green emission suitable for solid-state lighting and display technologies. This work not only demonstrates the potential of LAB:Tb3+ as a highly efficient green luminescent material, but also sheds light on the mechanisms responsible for energy transfer and concentration quenching.

An efficient ZnO and Ag/ZnO honeycomb nanosheets for catalytic green one-pot synthesis of coumarins through Knoevenagel condensation and antibacterial activity

Abstract This study pioneers the synthesis of porous Ag/ZnO nanosheets, focusing on their role as a catalyst in Knoevenagel condensation. Notably, these nanosheets display exceptional catalytic efficacy and captivating antibacterial properties. The research delves into the Ag/ZnO catalyst’s recyclability and proposes a potential reaction mechanism, marking the first comprehensive exploration of Knoevenagel condensation on porous Ag/ZnO nanosheets. Key findings underscore the successful synthesis of coumarin derivatives using various o-hydroxy benzaldehyde and 1,3-dicarbonyl compounds, with nano-Ag/ZnO serving as a catalyst via a monomode microwave-assisted approach. X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM) and UV–Vis spectroscopy were used in conjunction with other physicochemical methods to characterize the synthesized catalytic samples. The method boasts advantages such as high product yields, brief reaction durations, and the ability to reuse the catalyst for multiple cycles. The Ag/ZnO nanosheets, functioning as an acid catalyst, activate carbonyl groups and facilitate their interaction with methylene-containing active molecules. In addition, antibacterial activity assessments demonstrate the superior effectiveness of Ag/ZnO nanocomposites compared to ZnO nanosheets against Staphylococcus aureus germs. This multifaceted study not only advances catalytic synthesis but also unveils promising biological applications of porous Ag/ZnO nanosheets.

Green-synthesized chitosan‑carbon dot nanocomposite as turn-on aptasensor for detection and quantification of Leishmania infantum parasite

Leishmania is one of the most common diseases between human and animals, caused by Leishmania infantum parasite. Here, we have developed an ultra-selective turn-on fluorescent probe based on an aptamer and Chitosan-CD nanocomposite. The CD used in this study were synthesized using Quercus cap extract and a microwave-assisted approach. The Chitosan-CD nanocomposite was optimized using several microscopic and spectroscopic techniques to possess a bright fluorescence emission before adding aptamer and totally quenched fluorescence after addition of aptamer. The designed probe was proficient in the detection and quantification Leishmania infantum parasite by selective targeting of poly(A) binding protein (PABP) on the surface of the parasite. The designed fluorescent biosensor with high sensitivity, excellent selectivity, and a limit of detection (LOD) of 94 cells/mL of the Leishmania infantum parasite as well as a linear response in the ranges of 188–750 cells/mL and 3000–6000 cells/mL (R2 ≥ 0.98 for both linear ranges). Additionally, the selectivity of the designed probe was evaluated in the presence of different pathogenic species such as Trypanosoma brucei parasite and Staphylococcus aureus bacteria, as well as LiIF2α and LiP2a and BSA proteins as interference substances. The results of this study shows that using Chitosan-CD nanocomposite is a great strategy for developing selective turn-on probes with extraordinary accuracy and sensitivity in identifying Leishmania infantum parasite, especially in the early stages of the disease, and it is promising for the future clinical applications.