Microwave-assisted Heating Method Research Articles

Microwave-assisted synthesis of dual-functional NiSe2@NC nanocomposites for advanced power-type and energy-type storage devices

The battery-supercapacitor hybrid energy storage system, composed of energy-type and power-type storage devices, is essential to improve energy storage systems' comprehensive performance and economy significantly. The current research uses a convenient and economical microwave-assisted heating method to describe the preparation of NiSe2@NC nanocomposites with a core-shell carbon encapsulation structure. When used as an electrode material for power-type storage devices (Supercapacitors, SCs), the optimized NiSe2@NC-1-3 can achieve 555.7 F g−1 at 0.5 A g−1. The assembled asymmetric NiSe2@NC//AC has a wide operating voltage of 1.6 V and maintains 92.73 % durability after 10,000 cycles. For energy-type storage devices (Sodium-ion battery, SIBs) from the NiSe2@NC-1-3 electrode material exhibits a capacity of 384.4 mAh g−1 at 0.1 A g−1, a good rate capability (298.8 mAh g−1 at 5.0 A g−1), and excellent cycling life (311.7 mAh g−1 at 1.0 A g−1 for 1200 cycles). Considering the exceptional electrochemical performance of the NiSe2@NC nanocomposite in both power-type and energy-type storage devices, the rational design of this work will provide a new sight for the construction of a battery-supercapacitor hybrid energy storage system which will accelerate the rapid development of the world's energy storage.

Enhancing Intrinsic Electrocatalytic Activity of Pt/C Nanoparticles for Oxygen Reduction Reaction in Acidic Media by Microwave-Assisted Synthesis

Abstract: This study is focused on the enhancement of the intrinsic electrocatalytic activity of Pt nano-particles supported on C (Pt/C NPs) towards Oxygen Reduction Reaction (ORR) in acidic media. The goal was to investigate the effect of microwave-assisted synthesis on the electrocatalytic performance of Pt/C NPs towards ORR. Thus, Pt/C NPs were synthesized using a microwave-assisted method and by a conventional heating method; structural and morphological characteristics were analyzed by X-ray dif-fraction (XRD) and transmission electron microscopy (TEM). Electrochemical studies were performed using the rotating disk electrode technique to evaluate the ORR performance. Microwave-assisted syn-thesis produced Pt/C NPs with a smaller particle size (6.3 ± 0.2 nm) than conventionally synthesized nanoparticles (8.6 ± 0.3 nm). Electrochemical analysis showed that the microwave-synthesized Pt/C NPs exhibited higher mass activity (4.6 ± 0.8 mA･g-1Pt) for ORR compared to conventionally synthesized nanoparticles (1.9 ± 0.4 mA･mA･g-1Pt). These results demonstrate that microwave-assisted synthesis en-hances the intrinsic electrocatalytic activity of Pt/C NPs for ORR in acidic media. These findings have important implications for the development of efficient electrocatalysts for fuel cell applications. Background: The synthesis and characterization of platinum nanoparticles on C are crucial for advancing electrocatalysis, particularly in the context of potential applications in fuel cells. This study builds on previous research, focusing on two distinct synthesis methods to enhance our understanding of their im-pact on nanoparticle properties and electrocatalytic performance. Objective: To investigate the synthesis efficiency, structural characteristics, and electrocatalytic activities of platinum nanoparticles on C using microwave-assisted heating and conventional synthesis reactor heating. The objective is to discern any significant differences in particle size, structure, and electrocata-lytic performance between the two synthesis methods. Methods: The synthesis involved a comparative analysis of platinum nanoparticles using microwave-assisted and conventional heating methods. Chemical composition analysis verified the synthesis efficiency, and structural and morphological characterizations were performed using X-ray Diffraction and Transmission Electron Microscopy. Electrochemical studies employed the rotating disk electrode technique, with activation and evaluation conducted through cyclic voltammetry, and the oxygen reduction reaction studied via linear sweep voltammetry in an acidic media (0.5 mol⋅L-1 H2SO4). Results: Well-supported platinum nanoparticles with a face-centered cubic structure were obtained on C using both synthesis methods. However, microwave-synthesized particles (6.3 ± 0.2 nm) exhibited a smaller size compared to conventionally synthesized particles (8.6 ± 0.3 nm). Electrochemical assess-ment revealed superior mass activity for microwave-synthesized material (4.6 ± 0.8 mA･g-1Pt), outper-forming commercial Pt nanoparticles (3.0 ± 0.3 mA･g-1Pt) and conventionally synthesized material (1.9 ± 0.4 mA･mA･g-1Pt). Conclusion: This study concludes that microwave-assisted synthesis yields platinum nanoparticles on C with enhanced electrocatalytic performance, as evidenced by the smaller particle size and superior mass activity compared to conventionally synthesized material and commercial Pt nanoparticles. These findings highlight the potential of microwave-synthesized Pt nanoparticles for applications in fuel cells.

Insight into synthesis and characterisation of Ga0.9Fe2.1O4 superparamagnetic NPs for biomedical applications

A Ga3+-substituted spinel magnetite nanoparticles (NPs) with the formula Ga0.9Fe2.1O4 were synthesized using both the one-pot solvothermal decomposition method (TD) and the microwave-assisted heating method (MW). Stable colloidal solutions were obtained by using triethylene glycol, which served as a NPs stabilizer and as a reaction medium in both methods. A narrow size distribution of NPs, below 10 nm, was achieved through selected nucleation and growth. The composition, structure, morphology, and magnetic properties of the NPs were investigated using FTIR spectroscopy, thermal analysis (TA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and magnetic measurements. NPs with the expected spinel structure were obtained in the case of the TD method, while the MW method produced, additionally, an important amount of gallium suboxide. The NPs, especially those prepared by TD, have superparamagnetic behavior with 2.02 μB/f.u. at 300 K and 3.06 μB/f.u. at 4.2 K. For the MW sample these values are 0.5 μB/f.u. and 0.6 μB/f.u. at 300 K and 4.2 K, respectively. The MW prepared sample contains a secondary phase and very small NPs which affects both the dimensional distribution and the magnetic behavior of NPs. The NPs were tested in vitro on amniotic mesenchymal stem cells. It was shown that the cellular metabolism is active in the presence of Ga0.9Fe2.1O4 NPs and preserves an active biocompatible cytoskeleton.

Facile Microwave Synthesis of Efficient Green Emissive Carbon Dots Powder and Their Application in Visible Light Communication and White Light Emitting Devices

AbstractHighly green emissive solid‐state carbon dots (CDs) with photoluminescence quantum efficiency of 58% are prepared through a rapid microwave assisted heating method. Due to the spatial confinement from the biuret crystal matrix, aggregation among CDs is effectively suppressed, thus allowing the CDs to give efficient emission in the solid‐state. The CDs show excitation independent emission and mono‐exponential decay characteristics with a nearly constant lifetime of ≈13 ns upon varying the detected emissions, indicating the presence of a single type of emissive state in the CDs. Due to their high quantum efficiency and short lifetime, the obtained CDs are applied as the color conversion layer of a near‐ultraviolet micro light‐emitting diode (µLED) chip (405 nm) for visible light communication, achieving a modulation bandwidth of 165 MHz, which is much higher than the bandwidth of the conventional combination of Ce3+‐doped yttrium aluminum garnet phosphor with GaN LED. Moreover, the green emitting solid‐state CDs are applied to fabricate a prototype white LED device, which exhibits good lighting suitability with a color rendering index of 90.6 and a Commission Internationale de L'Eclairage chromaticity coordinates of (0.327, 0.332).

Transition Metal (Fe, Zn, Co, and Ni) Single-Atom Catalysts Anchored on N,S-Codoped Hybrid Nanocarbons for Oxygen Reduction Reaction

Atomically dispersed transition metal catalysts have served as promising candidates to substitute noble metals in energy conversion. A majority of carbon-supported transition metal single-atom catalysts (SACs) have been synthesized via the high-temperature sintering method, in which the complex heating and cooling processes are time- and energy-consuming. Herein, we have developed a simple and highly effective microwave-assisted heating method to prepare a series of isolated transition metal SACs anchored on a N,S-codoped nanocarbon matrix, which are denoted as M-NSC-MW, M = Fe, Zn, Co, and Ni. Among the various M-NSC-MW, Fe-NSC-MW possesses the highest ORR electrochemical activity in alkaline electrolytes. Its onset potential (Eonset) is 0.955 V, and its half-wave potential (E1/2) can reach 0.852 V, both of which are the same as those of commercial Pt/C. Moreover, Fe-NSC-MW also exhibits much superior ORR catalytic efficiency than conventional pyrolysis samples. It is worth noting that Zn-NSC–MW is prepared for the first time, and it also shows a high ORR performance with an Eonset of 0.945 V and an E1/2 of 0.832 V. This work has revealed the general application of the microwave-assisted heating method to prepare well-dispersed transition metal SACs anchored on the N,S-codoped graphene/carbon hybrid matrix.

A Turn-Off Fluorescent Biomimetic Sensor Based on a Molecularly Imprinted Polymer-Coated Amino-Functionalized Zirconium (IV) Metal-Organic Framework for the Ultrasensitive and Selective Detection of Trace Oxytetracycline in Milk.

Developing sensitive and effective methods to monitor oxytetracycline residues in food is of great significance for maintaining public health. Herein, a fluorescent sensor (NH2-UIO-66 (Zr)@MIP) based on a molecularly imprinted polymer-coated amino-functionalized zirconium (IV) metal-organic framework was successfully constructed and first used for the ultrasensitive determination of oxytetracycline. NH2-UIO-66 (Zr), with a maximum emission wavelength of 455 nm under 350 nm excitation, was prepared using a microwave-assisted heating method. The NH2-UIO-66 (Zr)@MIP sensor with specific recognition sites for oxytetracycline was then acquired by modifying a molecularly imprinted polymer on the surface of NH2-UIO-66 (Zr). The introduction of NH2-UIO-66 (Zr) as both a signal tag and supporter can strengthen the sensitivity of the fluorescence sensor. Thanks to the combination of the unique characteristics of the molecularly imprinted polymer and NH2-UIO-66 (Zr), the prepared sensor not only exhibited a sensitive fluorescence response, specific identification capabilities and a high selectivity for oxytetracycline, but also showed good fluorescence stability, satisfactory precision and reproducibility. The fabricated sensor displayed a fluorescent linear quenching in the OTC concentration range of 0.05-40 μg mL-1, with a detection limit of 0.012 μg mL-1. More importantly, the fluorescence sensor was finally applied for the detection of oxytetracycline in milk, and the results were comparable to those obtained using the HPLC approach. Hence, the NH2-UIO-66 (Zr)@MIP sensor possesses great application potential for the accurate evaluation of trace oxytetracycline in dairy products.

Comparison of DNA-Gold Nanoparticle Conjugation Methods: Application in Lateral Flow Nucleic Acid Biosensors.

Lateral flow nucleic acid biosensors (LFNABs) have attracted extensive attention due to their rapid turnaround time, low cost, and results that are visible to the naked eye. One of the key steps to develop LFNABs is to prepare DNA-gold nanoparticle (DNA-AuNP) conjugates, which affect the sensitivity of LFNABs significantly. To date, various conjugation methods-including the salt-aging method, microwave-assisted dry heating method, freeze-thaw method, low-pH method, and butanol dehydration method-have been reported to prepare DNA-AuNP conjugates. In this study, we conducted a comparative analysis of the analytical performances of LFNABs prepared with the above five conjugation methods, and we found that the butanol dehydration method gave the lowest detection limit. After systematic optimization, the LFNAB prepared with the butanol dehydration method had a detection limit of 5 pM for single-strand DNA, which is 100 times lower than that of the salt-aging method. The as-prepared LFNAB was applied to detect miRNA-21 in human serum, with satisfactory results. The butanol dehydration method thus offers a rapid conjugation approach to prepare DNA-AuNP conjugates for LFNABs, and it can also be extended to other types of DNA biosensors and biomedical applications.

A comparative study on graft copolymerization of MMA onto wood fiber under microwave and conventional heating

Wood polymer composites (WPC) are gaining popularity and widespread usage due to an increased awareness of human population towards the importance of environmental effects and green eco-friendly materials. Mechanical properties of WPC could be improved through graft copolymerization of monomer onto wood fiber to improve interfacial bonding. In this study, a comparison of free radical graft copolymerization using microwave-assisted and conventional heating method was performed. Methyl methacrylate (MMA) monomer is used in graft copolymerization of Meranti wood using a free radical initiator system consisting of ferrous sulfate and hydrogen peroxide. Grafting reaction time was varied while other graft parameters were kept constant including monomer concentration, initiator molar ratio, reaction temperature and solvent volume. Maximum graft yield of 11.75% and 10.17% were obtained for water bath heated and microwave-assisted method respectively. The presence of grafted monomer was proven by FTIR spectra analysis. Thermogravimetric analysis performed on grafted wood fibers showed improved thermal resistance compared to ungrafted wood fiber.

Constructing bimodal nanoprobe based on Gd:AgInS2/ZnS quantum dots for fluorometric/magnetic resonance imaging in mesenchymal stem cells

Mesenchymal stem cells (MSCs) hold great promise in regenerative medicine and received overwhelming concerns to promote their therapeutic effects. Owing to the shortage of MSCs-specific biomarkers, bimodal imaging nanoprobes with integrated complementary information are of great importance in ameliorating the efficacy of MSCs terminal tracking. In this study, a noninvasive dual-mode imaging nanoprobe with enhanced detection sensitivity and spatial resolution based on alloyed Gd:AgInS2/ZnS quantum dots (QDs) was first fabricated through a microwave-assisted heating method. The QDs with red emissive fluorescence exhibit excellent biocompatibility in MSCs under a confocal microscope. As for magnetic resonance imaging (MRI), the longitudinal relaxation rate of 11.1420 mM–1 S–1 of Gd:AgInS2/ZnS QDs was achieved, which was 1.7 times higher than that of commercial MRI contrast agent (6.4667 mM–1 S–1). Furthermore, the cellular internalization of Gd:AgInS2/ZnS QDs exerts no significant effect on the adipogenesis of MSCs and is conducive to the observation of further adipogenic differentiation. Our work helps to verify the promising prospect to develop a bimodal nanoprobe of fluorescence/MRI based on Gd:AgInS2/ZnS QDs, which could monitor the differentiation and migration of MSCs for further therapeutic approach.

Ultrafast microwave synthesis of MoTe2@graphene composites accelerating polysulfide conversion and promoting Li2S nucleation for high-performance Li-S batteries

In this report, MoTe2 nanosheets were grown on highly conductive graphene support through a simple and ultrafast microwave-assisted chemical coupling and heating method to develop hybrid sulfur host materials for Li-S batteries. MoTe2 nanosheets with superb electrocatalytic activity combined with highly conductive graphene form a nano reservoir for containing elemental sulfur, intermediate polysulfide species, discharge product Li2S, and accelerating the electron transfer. Accordingly, the Li-S battery with the MoTe2@graphene@carbon cloth electrode exhibited a high initial discharge capacity of 1246 mAh g−1 at 0.2C for the first galvanostatic cycle, good cycle stability (98.7% capacity retention after 100 cycles at 0.2C) and superb rate performance. The synergistic effect of the chemical affinity and superior electrocatalytic capability of polar MoTe2, along with the effective physical confinement by graphene and free-standing carbon cloth, provides a promising way to design host materials to mitigate the shuttling effect in rechargeable Li-S batteries.

Boosting cathodic hydrogen evolution with furfuryl alcohol oxidation as the anodic half-reaction for hybrid water splitting

Both anode feedstock and integrated electrodes are highly significant for the development of hybrid water electrolysis technology. Herein, biomass-derived furfuryl alcohol is selected as the anode feedstock, mainly because it contains no base-labile group (e.g., -CHO) and does not spontaneously undergo a Cannizzaro-type transformation under alkaline conditions. Bimetallic hydroxide nanowire arrays with nickel foam as the substrate (denoted Cu2Co(OH)x/NF) are designed and readily prepared via a microwave-assisted heating method. Then, Cu2Co(OH)x/NF is used as an integrated electrode for electrocatalytic furfuryl alcohol oxidation to value-added furoic acid with enhanced hydrogen production in 1.0 M NaOH. The input potential is reduced by approximately 219 mV when the oxygen evolution reaction is replaced by furfuryl alcohol oxidation to drive a current density of 10 mA cm−2. Moreover, the as-obtained electrode can be recycled several times without an obvious decline in carboxylate yield or Faradaic efficiency.

DNA Nanostructure-Guided Plasmon Coupling Architectures

DNA Nanostructure-Guided Plasmon Coupling Architectures

Synthesis of ZIF-8 tubular membrane via solvent evaporation seeding coupled with microwave assisted heating method for separation of small molecule gases

In this work, we systematically study the performance of tubular ZIF-8 membranes in the separation of small molecules including H2, CO2, N2 and CH4. The tubular ZIF-8 membranes were synthesized on α-alumina support via novel dual approach known as solvent evaporation seeding coupled with microwave assisted growth. The durations for the growth of the seed layer through solvent evaporation and membrane layer via microwave heating were varied. The crystallinity and morphology of the resultant membranes were evaluated by using XRD, SEM and IFM analyses. The performance of the resultant tubular ZIF-8 membranes was assessed for small molecule gases permeation at various pressures and temperatures. Highest flux ranging from 0.02 to 0.61 mol/m2s were obtained for gases CO2, CH4, N2, and H2 at feed pressure of 10 bar, whereas highest ideal selectivity of 12.4, 9.3 and 6.9 were obtained for H2/CH4, CO2/CH4, N2/CH4, respectively, at feed pressure of 10 bar and temperature of 30 °C. This work reveals that the tubular ZIF-8 membrane can be synthesized via a feasible and reproducible solvent evaporation seeding coupled with microwave assisted growth method, which can be further explored for the upscaling of the ZIF-8 tubular membrane in pilot scale for gas separation application.

Microwave-assisted synthesis of well-defined nitrogen doping configuration with high centrality in carbon to identify the active sites for electrochemical hydrogen peroxide production

While nitrogen (N)-doped carbon can facilitate the four-electron transfer in oxygen reduction reaction (ORR), its effect on the two-electron path is yet to be investigated. To date, the random N-C bond configurations in N-doped carbons make it difficult to identify the active sites for electrochemical reactions. Here, we report a preparation of well-controlled N-C configurations with high centrality as model catalysts for identification of active sites for two-electron transfer ORR. Specifically, the synthesized Pyrrolic-N doped single-wall carbon nanotube and graphene utilizing a microwave-assisted pulse heating method, exhibit excellent activity for two-electron path (H2O2 selectivity of 93.5% and 98.35%). X-ray adsorption near-edge structure spectroscopy measurements indicate that carbon atoms adjacent to Pyrrolic-N are the active sites for two-electron transfer. This work provides a viable way for the fabrication of tailored N configurations in carbon materials and significantly advances our understanding of the N moieties for the electrochemical H2O2 generation.

A confined carbon dot-based self-calibrated fluorescence probe for visible and highly sensitive moisture readouts

Excellent luminescent materials are essential for high-performance fluorescent nanosensors. Here, a new-type of self-calibrated humidity sensor is established through monitoring the fluorescent color change of carbon dots (CDs) confined in sodium hydroxide (CDs@NaOH). The CDs are prepared by a facile and rapid microwave-assisted heating method using citric acid, urea, and NaOH as precursors. The confinement effect from the NaOH reduces the nonradiative transition and suppresses the aggregation-induced quenching of the CDs in the solid. Compared with other sensors based on CD fluorescent visualization, the sensor has good linearity and a wide humidity-detection range from 6.9% to 95.4%. With the increased relative humidity, the fluorescence color of the sensor changes from green to blue. The proposed sensing mechanism is due to the breaking and reforming of hydrogen bonds and proton transfer occurring at the CD-NaOH matrix interfaces. These findings suggest a potential role for the spatial confinement effect and may provide an avenue for developing highly sensitive humidity readouts.

Microwave-assisted synthesis of self-assembly urchin-like ruthenium nanostructures in benzyl alcohol-glycerol mixed solvents

In this study, urchin-like ruthenium nanostructures (Ru NS), with an average size of approximately 30.2 nm, were successfully fabricated by reduction ruthenium chloride (RuCl3) in benzyl alcohol-glycerol mixed solvents, and using Polyvinylpyrrolidone (PVP) as the stabilizing agent under microwave irradiation for 240 s. The as-synthesized Ru NS were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), ultra violet-Visible (UV–Vis) absorption spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectra. The results indicated that the as-prepared urchin-like Ru NS were self-assemblies organized by smaller primary nanoparticles with an average size of about 1.7 nm. Some key factors, such as the microwave assisted heating method, and the types of solvents, were identified affecting the successful synthesis of self-assembly urchin-like Ru NS. A possible growth mechanism for the novel Ru structures has been proposed, and the urchin-like Ru NS have been formed through a self-assembly aggregation mechanism driven by an overgrowth mode.

Synthesis of ZSM-5 catalysts via microwave-assisted heating method for military jet fuel cracking into petroleum gas

Hydrothermal synthesis of ZSM-5 zeolites with different Si/Al ratios was conducted by using a microwave-assisted heating method. Their characteristics, such as morphology, porosity, acidity, and the catalytic performance for the cracking reaction of military jet fuel JP-8, were compared with ZSM-5 zeolites obtained via a conventional heating synthesis method. The microwave-assisted heating method contributed to bigger crystal sizes of the ZSM-5 zeolite as well as broader mesopore size distribution in the zeolite crystal with the same Si/Al ratio. Acidity analysis revealed ZSM-5 zeolites with similar acid properties could be produced with both heating methods. As the different heating methods attributed to different crystal sizes and roughness of the synthesized ZSM-5 zeolite, which are influenced by the fast crystal growth and consumption of silicon and aluminum precursor during the hydrothermal synthesis, different petroleum gas yields, and paraffinic product selectivity were observed from the ZSM-5 zeolite produced via microwave-assisted heating method. • Microwave-assisted heating method for hydrothermal synthesis (MH) of ZSM-5 zeolites were investigated. • MH method exhibited the same acidic properties but bigger and fairer surface of crystal due to fast crystallization. • Catalytic cracking reaction of military jet fuel was firstly explored with the ZSM-5 catalyst synthesized from MH method.

Microwave-assisted synthesis of self-assembled camellia-like CuS superstructure of ultra-thin nanosheets and exploration of its sodium ion storage properties

The major merit of this work is to use a facile microwave-assisted method to synthesize nanosheet-assembled camellia-like CuS material. When investigated as a novel anode for SIBs, the electrode exhibits an outstanding electrochemical performance. • A novel camellia-like CuS superstructure is first prepared by a microwave-assisted heating method. • Structural evolution is explained by the Ostwald ripening and oriented growth mechanism. • The CuS electrode shows excellent cycling stability and rate performance for SIBs. • The obtained nanosheet-assembled CuS anode delivers a large pseudocapacitive behavior. Layered copper sulfide (CuS) has immense commercial application potential in sodium-ion batteries (SIBs) due to its high capacity, diverse structures, and controllable synthetic methods. Despite these advantages, due to the large volume changes and soluble polysulfide intermediates based on the conversion reaction, it is a huge challenge for CuS electrodes to maintain high-rate performance and long-term cycle stability. Herein, a camellia-like CuS superstructure is designed and synthesized to improve cycling stability and rate performance. The cycling stability reflects in a stable capacity of 347.1 mAh g −1 can still be retained at 0.1 A g −1 after 100 cycles, and even after 1000 cycles at 5.0 A g −1 without decay. The excellent rate performance is embodied in the capacity of 352.4 and 255.7 mAh g −1 at 0.05 and 5.0 A g −1 , respectively. This work provides a feasible route to develop CuS anode material of SIBs with remarkable sodium storage performance.

Effect of a Novel Microwave-Assisted Induction Heating (MAIH) Technology on the Quality of Prepackaged Asian Hard Clam (Meretrix lusoria).

The microwave-assisted induction heating (MAIH) method—an emerging thermal technique—was studied to heat the prepackaged raw hard clam (Meretrix lusoria). The cooking effects on microbial and physiochemical qualities of clam were investigated. After the heating of the clam meat samples, the aerobic plate count (APC), psychrotrophic bacteria count (PBC), and total volatile basic nitrogen (TVBN) levels decreased with increasing heating time, but the shucking ratio, area shrinkage, and texture (hardness, cohesiveness, and chewiness) increased. In addition, the L* (lightness) and W (whiteness) of the clam meat samples increased significantly at the beginning of the heating period, whereas they decreased significantly with extended heating time. However, a* (redness) had the opposite trend. This study found that when clams were heated for more than 120 s at 130 °C or 150 s at 90 °C, they displayed obvious shrinking and a yellow-brown appearance, indicating that they are overcooked. After heating by MAIH for at least 110 s at 130 °C or 130 s at 90 °C, the samples were cooked well and gains a completely shucking, along with no microbial count detected. Therefore, the results indicated that the optimum heating conditions for prepackaged hard clams subjected to an MAIH machine were 130 °C for 110 s or 90 °C for 130 s.

Towards efficient carbon nanodot-based electromagnetic microwave absorption via nitrogen doping

The development of electromagnetic (EM) microwave absorption materials is essential for the whole electrical and electronic systems. Although carbon-based materials have been widely studied as EM absorber, the problems such as high cost, complicated processing technology and insufficient shielding performance still remain unsettled. Here, carbon nanodots (CDs) prepared through a one-step microwave-assisted heating method are demonstrated as EM absorption materials for the first time. With regulation of the doped nitrogen contents and degree of graphitization, the minimum EM reflection loss of the CDs at 10.7 GHz is −26.5 dB, and the effective absorption bandwidth of 1.5-mm thickness is 4.85 GHz. By adjusting the thickness, the effective absorption band ranges from 3.3 to 18 GHz, which is better than most non-composite carbon materials. The superior performance can be attributed to the excellent impedance matching and high dielectric loss in CDs. These results may extend the application fields of CDs and offer new insight into the exploitation of effective carbon-based EM shielding materials.