Short Reaction Times Research Articles

Microwave assisted synthesis of ion-imprinted polyacrylonitrile fibre via one-step phosphorylation for selective recovery of Dy(III) from wastewater

The selective recovery of Dy(III) from wastewater is highly desirable. Ion imprinted fibers are considered as attractive adsorbents due to their low flow resistance, high selectivity and ease of recovery. Phosphate groups with strong affinity to rare earth ions are widely used to construct ion imprinted polymers. However, current approaches for introducing phosphate groups into fibers suffer from the low grafting percentage and long reaction time because of the complicated procedures. Herein, a simple one-step phosphorylation method was explored to simultaneously introduce highly active primary amine and phosphate groups into polyacrylonitrile fiber (PANF) under microwave assisted conditions. Additionally, an unique Dy(III) ion-imprinted fibrous adsorbent (IIF-3) was fabricated by cross-linking of the aminated and phosphorylated PANF for selective capture of Dy(III) from wastewater. The advantages of this innovative technology in synthesizing fibrous adsorbent include: short reaction time, high phosphonic content and good mechanical property. In addition, batch sorption tests reveal that the uptake of Dy(III) onto IIF-3 is well described by the Langmuir isotherm and pseudo-second order models. Besides, IIF-3 exhibits a high adsorption selectivity for Dy(III) in multi-component system with different types of interfering ions. Importantly, benefiting from the protective effect of surface imprinting layer, the IIF-3 not only achieves enhanced mechanical property, but also shows satisfied reusability in six times application. This work opens a novel path to prepare phosphorylated ion-imprinted fibers and sheds light on their applications for selective capture of Dy(III) from wastewater.

Microwave-assisted Green Synthetic Approach towards Water Dispersible Luminescent PVP-coated Tb3+ and Ce3+/Tb3+-doped KZnF3 Nanocrystals

Background: Perovskite fluoride nanomaterials are an interesting research topic in material science due to their exciting properties like high-temperature superconductivity, magnetic behaviour, piezoelectric behaviour, etc. Doping of lanthanide ions into the perovskite fluoride nanomaterials makes them more promising as they have applications from biological label-ling to multicolor optical devices. Objective: This study aimed to carry out the synthesis of perovskite KZnF3 nanocrystals in an eco-friendly environment with the help of a microwave-assisted route in a shorter reaction time and at low temperatures. Moreover, it aimed to make the nanocrystals water dispersible, illuminating brighter photoluminescence, which was achieved by coating nanocrystals surface with poly(N-vi-nyl-2-pyrrolidone) and doping of different lanthanide ions (Ln= Tb3+ and Ce3+/Tb3+) respectively, into the KZnF3 nanocrystals matrix. Methods: The synthesis of nanocrystals was performed in an environment-friendly microwave-assisted way and under green conditions. For example, in the preparation of Tb3+(5mol%)-doped KZnF3 nanocrystals, 0.95 mmol of Zn(NO3)2 and 0.05 mmol of Tb(NO3)3 were dissolved in 8 mL of distilled water. Then, an 8 mL aqueous solution of KF (3 mmol) was added to it. The entire mixture was stirred well for 15 minutes. About 60 mg of PVP was added to the mixture and stirred for another 15 minutes. Then, a microwave reaction vessel was made by transferring the final reaction mixture into it and kept under microwave irradiation at 90°C temperature for 15 minutes. Finally, the product was cooled to room temperature and collected by centrifugation. Results: Both Tb3+(5mol%)-doped and Ce3+(15mol%)/Tb3+(5mol%) co-doped KZnF3 nanocrystals exhibit very strong green photoluminescence. The structural and optical properties of as-obtained nanocrystals were characterized by PXRD, field emission scanning electron microscopy, Fourier infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, and photoluminescence spectra. Conclusion: The nanocrystals with uniform cubical morphology having ~60 nm sizes were successfully synthesized. The high photoluminescence efficiency, together with the water dispersibility of the nanocrystals, makes the material useful in many fields of optical devices and offers several biological applications. Moreover, this method could be used to make other lanthanide-doped perovskite fluoride nanocrystals.

Magnesium Powder-Catalyzed, Highly Efficient, Solvent-Free Synthesis of Amides through N-Acetylation of Amines and their Antibacterial Activity

Magnesium powder was found to be an efficient catalyst for the acetylation of amines (1) with Ac2O affording corresponding amides (2) in excellent yields (> 99%). This green synthetic protocol has utilized 2.5 mol% of magnesium powder and a stoichiometric amount of Ac2O (1.2 equiv.). Amides 2a-k were synthesized within a short reaction time (2-3 min) at an ambient temperature under solvent free condition. The products were screened against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis bacterial strains. N-(2-Hydroxyphenyl)acetamide (2f) was found most active against Gram-positive S. aureus and S. epidermidis indicating its efficacy in treating skin diseases.

Mechanism Analysis and Experimental Research on Leaching Zn from Zinc Oxide Dust with an Ultrasound-Enhanced NH3-NH4Cl-H2O System

Zinc oxide dust (ZOD) is an industrial solid waste produced in the production process of wet smelting Zn, with large output and great pollution to the environment. The recycling of metallurgical solid waste such as zinc oxide dust is very important to achieve the sustainable development of the circular economy. An experimental study of zinc (Zn) leaching from zinc oxide dust using an ultrasound-enhanced ammonia–ammonium chloride system was performed. The effects of ultrasonic power, leaching time, total ammonia concentration, and other factors on the leaching rate of zinc from zinc oxide dust were investigated. The results revealed that the leaching rate of Zn reached up to 80.70% under the condition of ultrasound power of 1000 W, reaction time of 15 min, total ammonia concentration of 6 mol/L, [NH3]:[NH4+] of 1:1, L/S of 5:1, temperature of 45 °C, and stirring speed of 100 r/min. The conventional leaching was conducted under similar conditions, except that the time was controlled to 40 min and the zinc leaching rate was 71.15%. The leaching rate of Zn in the ultrasound condition was improved by 9.55% compared with that in the conventional leaching process. XRD, laser particle size, and SEM-EDS analyses were conducted to study the leaching residues of ZOD. The analysis results showed that in the ultrasound condition, the largest leaching rate of soluble ZnO phases was achieved after 15 min of leaching. Under the ammoniacal system, it was difficult to leach ZnFe2O4, Zn2SiO4, and ZnS phases, which partly accounted for the low zinc leaching rate. Additionally, through ultrasound-enhanced treatment, the ZnO particles encapsulated in ZOD particles were broken into smaller sizes and exposed to the leaching solution. Thus, the leaching rate of Zn was improved. The experimental results show that ultrasound can tremendously improve the effect of Zn extraction from ZOD, shorten reaction time, and help reduce energy consumption and environmental pollution, making it a promising application in the treatment of secondary Zn resources.

Abnormal multisensory temporal discrimination in Parkinson’s disease

Cognitive deficits are prevalent in Parkinson’s disease (PD), ranging from mild deficits in perception and executive function to severe dementia. Multisensory integration (MSI), the ability to pool information from different sensory modalities to form a combined, coherent perception of the environment, is known to be impaired in PD. This study investigated the disruption of audiovisual MSI in PD patients by evaluating temporal discrimination ability between auditory and visual stimuli with different stimulus onset asynchronies (SOAs). The experiment was conducted with Fifteen PD patients and fifteen age-matched healthy controls where participants were requested to report whether the audiovisual stimuli pairs were temporal simultaneous. The temporal binding window (TBW), the time during which sensory modalities are perceived as synchronous, was adapted as the comparison index between PD patients and healthy individuals. Our results showed that PD patients had a significantly wider TBW than healthy controls, indicating abnormal audiovisual temporal discrimination. Furthermore, PD patients had more difficulty in discriminating temporal asynchrony in visual-first, but not in auditory-first stimuli, compared to healthy controls. In contrast, no significant difference was observed for auditory-first stimuli. PD patients also had shorter reaction times than healthy controls regardless of stimulus priority. Together, our findings point to abnormal audiovisual temporal discrimination, a major component of MSI irregularity, in PD patients. These results have important implications for future models of MSI experiments and models that aim to uncover the underlying mechanism of MSI in patients afflicted with PD.

Immobilization of ionic liquids (ILs) on magnetic mesoporous silica nanotubes: A high throughput and reusable nanocatalyst for the green synthesis of indeno[1,2-b]indolone derivatives

The acidic ionic liquid supported on the magnetic mesoporous silica nanotubes (M-MSNTs/IL) was prepared as a new magnetic catalyst and fully characterized with FE-SEM, HR-TEM, EDS, TGA, BET, VSM, FT-IR, EDX, elemental mapping and XPS. The template of catalyst was magnetic aminated MWCNTs (M-MWCNTs/CONHBu), which removed through calcination process and magnetic mesoporous silica nanotubes (M-MSNTs) were obtained and functionalized using adenine based ionic liquid. The prepared catalyst was successfully applied as a new reusable heterogeneous catalyst for the one-pot three-component indeno[1,2-b]indole-9,10-dione derivatives in water at 75 °C. All of desired products were obtained in good to excellent yields (79–96 %) after relatively short reaction times. M-MSNTs/IL also exhibited a remarkable performance with TOF of 61.2 h-1 and TON of 86.7. The use of M-MSNTs/IL catalyst in the synthesis of indeno[1,2-b]indole-9,10-dione derivatives revealed several advantages including mild reaction conditions, high yield of pure products, clean reaction conditions, avoiding the production of toxic waste, chemical stability of the catalyst, low amount and reusability of catalyst. In addition, the applied nanocatalyst was recovered with an external magnet and reused 6 times without considerable reduction in its catalytic activity.

Nanoporous aluminosilicate mediated synthesis of 2- and 2,2-substituted 2,3-dihydroquinazolin-4(1H)-ones

Nanoporous silicate materials, made by an operationally simple evaporation-induced self-assembly (EISA) approach, efficiently catalyze the formation of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones from aldehydes and dimethyl acetals. This methodology can be extended to encompass the reaction of ketones and ketals to provide facile access to 2,2-disubstituted and spiro dihydroquinazolin-4(1H)-ones in high yields and short reaction times.

Towards environmental protection and safety coloration process in wool fibers: Role of disperse reactive dyes structure

Traditional wool fibers dyeing uses a huge amount of water and energy, and relies on lots of chemicals, which produces huge amounts of lower-biodegradable wastewater, and poses a great threat to the water environment. Here, to investigate the role of disperse reactive dyes structure on the dyeing properties, a sustainable waterless dyeing of wool fibers was investigated with four synthesized disperse reactive dyes by using supercritical CO2 as a non-aqueous dyeing medium. The effects of dyeing time, pressure, temperature and dye concentration on the dyeing properties were discussed. The results showed that K/S values up to 5.5 under the optimal dyeing condition of 383.15 K, 23 MPa, and 70 min were obtained, indicating shorter reaction time and higher K/S values compared to similar studies. Moreover, excellent colorfastness to soaping and rubbing up to 4–5 was displayed since nucleophilic substitution reaction occurs between the C atom on the triazine group of disperse reactive dyes and -NH2 on the cysteine of fiber macromolecules. This study provides an environmental protection and safety coloration process to produce high-quality wool fiber products by establishing the relationship between structure of disperse reactive dyes and dyeing properties of wool.

Scope and Limitations of Using Microemulsions for the Covalent Patterning of Graphene.

Patterning of graphene (functionalizing some areas while leaving others intact) is challenging, as all the C atoms in the basal plane are identical, but it is also desirable for a variety of applications, like opening a bandgap in the electronic structure of graphene. Several methods have been reported to pattern graphene, but most of them are very technologically intensive. Recently, we reported the use of microemulsions as templates to pattern graphene at the μm scale. This method is very simple and in principle tunable, as emulsions of different droplet size and composition can be prepared easily. Here, we explore in detail the scope of this methodology by applying it to all the combinations of four different emulsions and three different organic reagents, and characterizing the resulting substrates exhaustively through Raman, SEM and AFM. We find that the method is general, works better when the reactive species are outside the micelles, and requires reactive species that involve short reaction times.

Acoustic cavitation oxidation of ionic liquids: A brief review

AbstractIonic liquids (ILs) are third‐generation materials with broad industrial applications. However, their toxicity, non‐biodegradability and water solubility render them persistent water pollutants. Consequently, IL degradation from water is an emerging topic of research interest nowadays. Sonolysis is one of the advanced oxidation processes (AOPs) based on ultrasound (US). During sonolysis, acoustic cavitation decomposes water into reactive hydroxyl (•OH) and hydrogen (•H) radicals, which then oxidize IL. This review discussed different AOPs for wastewater treatment reflecting their shortcomings, with a special focus on the operating conditions and effectiveness of US‐based hybrid AOPs for IL degradation. The synergistic effects of US over other AOPs are investigated. Hybid‐sonolysis has proven to significantly enhance IL mineralization in shorter reaction time by generating more reactive‐free radicals in an aqueous medium at experimentally optimized conditions. Finally, this review identifies research gap and proposes future directions of IL degradation. It will serve as a valuable resource for future studies of IL degradation using US techniques.

Microwave-assisted Transfer Hydrogenation of Carbonyl and Nitro Compounds by Bimetallic Ru(II) cymene Complexes

We report on the investigations of microwave-assisted catalytic transfer hydrogenation (TH) of carbonyl and nitro compounds by employing Ru(II) complexes bimetallic [(p-cymene)2(RuCl)2L1]2X (X = BF4 (Cat2); X = PF6 (Cat3)) and mononuclear [(p-cymene)(RuCl)L2]BF4 (Cat4) (where L1 = N,N'-(3,3',5,5'-tetraisopropyl-[1,1'-biphenyl]-4,4'-diyl)bis(1-(pyridin-2-yl)methanimine); L2 = N-(2,6-diisopropyl-phenyl)-1-(pyridin-2-yl)-methanimine). At a low catalyst loading of 0.01 mol% (Cat2/Cat3), a broad substrate scope has been achieved for aromatic as well as aliphatic ketones and aldehydes, with a short reaction time of just 10 minutes. Additionally, chemoselective hydrogenation of nitroaromatic compounds has been achieved under microwave irradiation by Cat2 within 5 minutes. Control experiments demonstrate that microwave heating conditions outperform conventional heating method in terms of improved catalytic activity and reaction efficiency. The bimetallic Cat2 catalyst can be used at a very low loading of 0.001 mol% to achieve the high TONs and TOFs of 7.7 × 104 and 2.3 × 105 h-1, respectively, for TH reaction. Spectrometry experiments for intermediate trapping have been used to propose a probable mechanism for TH of carbonyl compounds.

Chitosan-sulfonic acid-catalyzed green synthesis of naphthalene-based azines as potential anticancer agents.

Aim: This study focuses on advancing green chemistry in anticancer drug discovery, particularly through the synthesis of azine derivatives with a naphthalene core using CS-SO3H as a catalyst. Methods: Novel benzaldazine and ketazine derivatives were synthesized using (E)-(naphthalen-1-ylmethylene)hydrazine and various carbonyl compounds. The methods employed included thermal and grinding techniques, utilizing CS-SO3H as an eco-friendly and cost-effective catalyst. Results: The approach resulted in high yields, short reaction times and demonstrated catalyst reusability. Cytotoxicity tests highlighted compounds 3b, 11 and 13 as potent against the HEPG2-1. Conclusion: This study successfully aligns with the objectives of eco-conscious drug development in organic chemistry. Molecular docking and in silico studies further indicate the potential of these ligands as antitumor medicines, with favorable oral bioavailability properties.

Recent Advancements in the Utilization of s-Block Organometallic Reagents in Organic Synthesis with Sustainable Solvents.

This mini-review offers a comprehensive overview of the advancements made over the last three years in utilizing highly polar s-block organometallic reagents (specifically, RLi, RNa and RMgX compounds) in organic synthesis run under bench-type reaction conditions. These conditions involve exposure to air/moisture and are carried out at room temperature, with the use of sustainable solvents as reaction media. In the examples provided, the adoption of Deep Eutectic Solvents (DESs) or even water as non-conventional and protic reaction media has not only replicated the traditional chemistry of these organometallic reagents in conventional and toxic volatile organic compounds under Schlenk-type reaction conditions (typically involving low temperatures of -78 °C to 0 °C and a protective atmosphere of N2 or Ar), but has also resulted in higher conversions and selectivities within remarkably short reaction times (measured in s/min). Furthermore, the application of the aforementioned polar organometallics under bench-type reaction conditions (at room temperature/under air) has been extended to other environmentally responsible reaction media, such as more sustainable ethereal solvents (e.g., CPME or 2-MeTHF). Notably, this innovative approach contributes to enhancing the overall sustainability of s-block-metal-mediated organic processes, thereby aligning with several key principles of Green Chemistry.

Asymmetric synthesis of enantiopure tetracyclic dispirooxindolopyrrolidine-piperidones via microwave-assisted multicomponent reaction: Crystallographic analysis, antimicrobial activity and in silico studies

In an attempt towards the development of new antimicrobials, we synthesized by microwave-assisted multicomponent reaction (MCR) of enantiopure (E,E)-3,5-bisarylidene-N-[(S)-(-)-methylbenzyl]-4-piperidones, isatin and α-amino esters a series of optically active tetracyclic dispirooxindolopyrrolidine-piperidones. The beneficial and promising features of this protocol such as simple operational procedure, short reaction time (10 min), and high product yields (up to 97 %) make it an efficient eco-friendly approach offering a powerful mean to expand the structural diversity of spirooxindoles. This approach appears hugely advantageous for high-throughput screening processes in drug discovery research. In addition, crystallographic parameters and inter- and intramolecular interactions occurring in spiropyrrolidine-fused piperidone derivative 4g were examined through single-crystal XRD analysis allowing to determine the absolute configuration of the enantiopure compound. The preliminary biological assessment of their antimicrobial activity indicates that most of the screened products display higher activity than the standard reference drugs Ampicillin and Griseofulvin. Some of them exhibited good to moderate activity against both bacteria and fungi. In addition, in silico molecular docking and predictive ADMET studies for the most active spirocompounds were carried out. Molecular docking confirmed the binding efficacy of candidates 4c and 4l through low score energy values and the establishment of diverse bonding interactions with the active site residues. Finally, the ADMET profiling of the most active spiroheterocycles proved their remarkable drug-like and pharmacokinetic properties.

Calcined Biowaste Durian Peel as a Heterogeneous Catalyst for Room-Temperature Biodiesel Production Using a Homogenizer Device.

Calcined biowaste durian peel (BDP) contains 86% potassium element as the main compound and has successfully catalyzed the transesterification of palm oil to biodiesel at room temperature. The effect of catalyst weight, molar ratio of palm oil to methanol, reaction time, and rotational speed of the homogenizer device was investigated on biodiesel conversion and yield. The highest biodiesel conversion of 97.4 ± 0.3% was achieved using the following reaction conditions: a catalyst weight of 5 wt %, a molar ratio of palm oil to methanol of 1:15, a reaction time of 10 min, and a rotational speed of 6000 rpm. Unfortunately, calcined BDP could not hold its catalytic activity in the reusability study. The biodiesel conversion was decreased in the second cycle due to the decrease of both catalyst weight and concentration of potassium ions after the first cycle. However, the calcined BDP paired with a homogenizer device could produce biodiesel in a short reaction time and at room temperature.

Polyethyleneimine-immobilized CoCl2 nanoparticles: Synthesis, characterization, application as a new efficient and reusable nanocomposite catalyst for one-step transesterification reaction

Polyethyleneimine-supported cobalt (II) chloride as a novel polymeric nanocomposite acidic catalyst for the one-stage transesterification reaction of ethyl acetate with various alcohols is reported. The catalyst was characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, scanning electron microscopy, dynamic light scattering technique, and thermal gravimetric analysis. Furthermore, inductively coupled plasma and atomic absorption spectroscopy were used to determine the quantity of Cobalt nanoparticles in the catalyst. By adding the catalyst (0.10 g, 0.20 mol%) and n-hexane/chloroform (5.0 cm3) as solvent under reflux conditions, the studies demonstrated successful transesterification reactions with excellent yields (80–98%) and short reaction times (0.50–1.30 h) using various substrates on the scale of 1.0 mmol. Seven consecutive reactions could be performed on the catalyst without significantly decreasing its activity. The most noteworthy aspects of this process are its low cost, safety, and environmental friendliness due to the catalyst’s non-toxicity, straightforward operation, and effective outcomes.

Nano MgCuAl2O5: Synthesis by Sol-Gel Auto-Combustion Process, Characterization and Reusable Heterogeneous Catalyst for the Hantzsch 1,4-Dihydropyridine Reaction

For the first time, MgCuAl2O5 heterogeneous nanocatalysts were prepared by sol-gel auto-combustion method, which displayed great yield and suitable activity for the preparation of 1,4-DHP derivatives with high efficiency in green solvent ethanol/water (1:1) at 80 °C under one pot condition. The synthesis materials were separated in short reaction times with excellent yield (80–95) %. Moreover, the synthesized nanocatalyst was easily retrieved and continuously reused for six reactions without a noticeable significant loss of proficiency. The solid catalyst was confirmed by XRD, BET, FTIR, FESEM and EDX, and the substituted 1,4-dihydropyridines were characterized by melting point, 1H and 13C NMR.

A Novel One-Pot Three-Component Approach to Orthoaminocarbonitrile Tetrahydronaphthalenes Using Triethylamine (Et_3N) as a Highly Efficient and Homogeneous Catalyst Under Mild Conditions and Investigating Its Anti-cancer Properties Through Molecular Docking Studies and Calculations

An efficient and environmentally friendly method for the one-pot synthesis of ortho-aminocarbonitrile tetrahydronaphthalenes has been developed in the presence of triethylamine (Et3N) as a homogeneous catalyst. The multicomponent reactions of benzaldehydes, cyclohexanone and malononitrile were carried out under mild conditions to obtain some ortho-aminocarbonitrile tetrahydronaphthalene derivatives. A broad range of structurally diverse benzaldehydes were applied successfully, and corresponding products (4A-L) were obtained in good to excellent yields (87-98%) in very short times (10-25 minutes). The present approach provides several advantages including simple workup, high yields, very mild reaction conditions, short reaction times, little catalyst loading and not requiring specialized equipment. Furthermore, with the help of computational chemistry and drug design methods, the anti-cancer properties of these compounds were studied and investigated. All the synthesized compounds bind to an agonist at the active site of the 3A8P protein, which leads to the inactivation of this protein and produces beneficial effects during cancer treatment. In synthesized compounds, the ligands establish hydrogen bonds with leucine A:728 residues through nitrogen, which has a very special and vital role in biological sciences and pharmaceutical connections. In this study, it was found that these compounds have the potential to become an oral anti-cancer drug.

Water-Doped Brønsted Acidic Protic Ionic Liquids for Enhanced Tributyl Citrate Synthesis in a Two-Phase Esterification System.

Tributyl citrate (TBC) plays a crucial role as a plasticizer, enhancing the flexibility of polymers such as polyvinyl chloride. Its biodegradability and non-toxic nature contribute to eco-friendly appeal, making it a preferred additive in diverse industries, including food packaging, medical devices, toys, and consumer goods. Herein, a method for the synthesis of TBC using inexpensive Brønsted acidic protic ionic liquids (ILs) in a two-phase reaction system is presented. The esterification process is carried out with high yield (>99 %), selectivity (up to 98 %) and short reaction time of 2 h. The catalyst in the form of IL shows excellent performance and stability, desirable for industrial applications.

A 90- followed by a 30-min nap reduces fatigue whereas a 30- followed by a 90-min nap maintains cognitive performance in night work: A randomized crossover-pilot study

ObjectiveTo investigate the effects of combinations of brief naps (a 90- followed by a 30-min nap vs. a 30- followed by a 90-min nap) on sleep inertia, reducing sleepiness and fatigue, and maintaining performance during night hours. MethodsThis randomized, comparative, repeated-measure, cross-over study investigated subjective and cognitive performance in 12 healthy females, evaluated in three experimental nap conditions: 1) from 22:30 to 00:00 and 02:30 to 03:00 (Pre90-NAP group), 2) from 23:30 to 00:00 and 02:30 to 04:00 (Pre30-NAP) group, and 3) no naps (NO-NAP group). Participants’ body temperature, psychomotor vigilance task (PVT) and Uchida-Kraepelin test (UKT) scores, and subjective feelings of drowsiness and fatigue were evaluated. Sleep state was determined by an actigraphy monitoring device worn by participants. ResultsRegardless of timing, both 90-min naps were associated with sleep inertia, and both 30-min naps with minimal sleep inertia. Reaction times were shorter and fewer errors were committed at 2 h post-nap in the Pre30-NAP and Pre90-NAP groups compared with those at the same time in the NO-NAP group. Adding a 90-min nap to a 30-min nap reduced subjective fatigue and shortened reaction times, and adding a 30-min nap to a 90-min nap was effective in maintaining performance, suggesting a synergistic effect. ConclusionsTaking two naps during a night work can mitigate sleepiness and fatigue, and maintain performance. A 90- followed by a 30-min nap reduced fatigue and reaction time, and a 30- followed by a 90-min nap maintained cognitive performance in the early morning.