Asia-Pacific Journal of Chemical Engineering

Corrosion remains a critical challenge across various industries, particularly affecting the longevity and safety of metallic materials. To combat this issue, intelligent anti‐corrosive coatings have emerged as a promising solution, incorporating micro/nano carriers that store and release corrosion inhibitors in response to specific stimuli. These advanced coatings have demonstrated the ability to significantly enhance the electrochemical impedance of steel, offering superior protection compared to conventional coatings. Among the innovative materials explored for this purpose, covalent organic frameworks (COFs) have garnered attention for their exceptional potential as nanocarriers. COFs are characterized by their high surface area, tunable porosity, and chemical versatility, making them ideal for improving corrosion resistance. This review highlights recent advancements in the use of COFs for intelligent anti‐corrosive coatings, focusing on essential design factors such as carrier compatibility, stability, stimuli‐responsive properties, synthesis techniques, and underlying mechanisms. Despite their relatively recent discovery, COFs have shown remarkable promise in enhancing the durability and reliability of anti‐corrosive coatings. The review also addresses the existing challenges for COF‐based nanocarriers in corrosion protection and explores their future potential in this field.

Biomaterials‐based triboelectric nanogenerators (TENG) are outstanding components in self‐powered electronic devices for healthcare monitoring systems. However, addressing the durability, performance, and cost of production of these devices remains a significant research challenge. In this study, we propose a simple solution casting technique to fabricate thin films of polylactic acid (PLA) nanocomposites for TENG applications. Initially, different transition metal‐doped iron oxide (Fe2O3) nanoparticles were synthesized via a hydrothermal process and subsequently doped with Co, Ni, and Mn. The morphological analysis techniques, SEM and AFM, were used to explore the structural properties of doped nanoparticles, while the TGA and DSC techniques were employed to investigate the thermal stability and crystalline behavior of nanocomposites. Dielectric property analysis revealed shorter relaxation times for the doped nanoparticle‐containing composites. Notably, PLA/Mn‐doped and PLA/Co‐doped nanocomposites exhibited the highest triboelectric properties, which can be attributed to their specific characteristics.

AbstractControlling anionic redox is the crucial factor for the commercialisation of Li‐Rich cathodes, being required to achieve high practical specific capacity of >250 mAh/g for long‐term cycling. However, the lack of generalizable understanding of the activation and anionic redox mechanisms complicates the rational design of robust Li‐rich cathodes towards practical applications. We find that the physical evolution during activation is only weakly correlated with performance, with structural change seemingly triggered by low‐voltage irreversible anionic redox. Structural evolution is undoubtedly important to the long‐term performance of the battery; however, we find that the electronic structure at the beginning of activation (~4.5 V) is the most important parameter for reversibility. Activation at low voltages triggers large scale structural change, which can in turn trigger more irreversible oxygen oxidation in a feedback loop. Our results suggest that three most cited activation mechanisms – the Reductive Coupling mechanism, the Reversible Transition Metal Migration mechanism, and the Transition Metal Layer Nanovoids theory – all play an important role in this feedback loop. Future optimisations of Li‐Rich cathodes must therefore consider the interactions between all mechanisms holistically, rather than designing around one activation mechanism exclusively.

AbstractIn the present study, a Ni doped bimetallic sulfide Ni‐MoS2@SnS2 flower‐like nanocomposite is synthesized via a facile one‐step solvothermal method. The Ni‐MoS2@SnS2 with the unique structure and composition demonstrates superior supercapacitor performance (a specific capacitance of approximate 1150, and 878 F cm−2 at the current density of 0.5 mA cm−2 and 5 mA cm−2, respectively) in comparison to sole SnS2 (a specific capacitance of about 486, and 445 F cm−2 at the same parameters). This remarkable enhancement in the electrochemical performance of Ni‐MoS2@SnS2 may be attributed to synergic effect of bimetallic sulfides with flower‐like structure as fast electronic transport and minimal volume variation of the formation of nanocomposite. More precisely, it exhibits 57.53 Wh kg−1, 1500.78 W kg−1 energy and power density at 0.5 mA cm−2, respectively, along with the better capacity retention of 85.2 % at 1 mA cm−2 even after 5000 constructive charge‐discharge cycles. It is viable approach for the development and design of novel type electrode materials featuring with flower ‐like structure is proposed to enhance the structural stability of supercapacitor.

AbstractElectrochemical nitrate reduction reaction (NO3RR) has received universal attention to synthesize value‐added ammonia, which requires high‐efficiency catalysts to reduce the reaction barrier. Herein, cobalt doped SrFeO3 nanofibers (SCFO) with abundant oxygen vacancies via electrospinning technique is proposed to convert nitrate to ammonia. Such catalyst achieves an optimum Faradaic efficiency of 81.5 % and a high NH₃ yield of 16.1 mg h−1 mg−1cat. in a 0.1 M PBS + 0.1 M NaNO₃ solution at −0.9 V reversible hydrogen electrode (RHE). Moreover, the in‐situ electrochemical test and DFT calculations confirm the potential‐determining step (PDS) for SCFO is *NO−*N with an energy barrier of only 1.28 eV.

AbstractThe hydrogen evolution reaction (HER) produces (di)hydrogen (H2), a clean energy carrier, through the cathodic side of the water splitting reaction. Specifically, this method of producing hydrogen is applicable to converting clean electricity and/or solar energy into a chemical fuel. Herein, a cobalt(pyridinethiolate N‐oxide)2 complex was synthesized through the reaction of cobalt sulfate with the aforementioned ligand and shown to be a four coordinate paramagnetic cobalt complex using paramagnetic nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, and mass spectrometry. This complex was then tested for HER activity in homogeneous phase and embedded into reduced graphene oxide thin films and physisorbed onto a graphite rod electrode. Despite its similarity to other highly active molecular catalysts for HER, surprisingly, this complex did not show any reliable HER activity. Instead, in acidic DMF, HER active nanoparticles were reductively deposited onto a glassy carbon electrode. This is the first example, to the best of our knowledge, of a molecular cobalt thiolate complex that decomposes to make nanoparticles upon electrolysis rather than acting as a molecular catalyst for HER. The ellipsoidal Co nanoparticles were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), SEM energy‐dispersive X‐ray spectroscopy (EDS), X‐ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP‐MS). The amount of deposited material, and the size and number of nanoparticles, was shown to increase with the number of deposition scans. Cyclic voltammetry scans showed that the onset potential for HER decreases and the catalytic current increases with the diameter of the nanoparticles. A drop‐cast Nafion thin film improved the durability of the nanoparticle‐covered electrodes, allowing for HER for at least 8 hrs. These electrodes have a Faradaic efficiency of 100±3 %, and produce 14.1 mmol H2 per gram Co per second, at pH 1. The complex cobalt bis(mpo) is thus identified as an ideal precursor for the controlled electrodeposition of metallic Co nanoparticles with a defined size and shape.

AbstractHydroxyapatite (HAp) is a well‐known precursor for synthesizing different bionanocomposite products for biomedical applications. For the first time, we aimed to evaluate the effects of plasma surface functionalization of HAp nanoparticles (NPs) on the chemical, physical, and bio‐functional properties of chitosan films using experimental and computational evaluations. Atmospheric air plasma process was conducted on HAp NPs at two different air pressures (650 and 1300 mTorr) and four different exposure times (1, 3, 6, and 9 min), followed by fabrication of HAp/chitosan bionanocomposites. Fourier transform infrared (FTIR) spectra proved that the position of bands at 1639 and 1037 cm−1 were shifted to 1635 and 1031 cm−1 due to the interaction between chitosan amine groups and HAp phosphate groups. Quantum mechanical and molecular dynamic (MD) simulations were used to understand the interactions between chitosan and HAp. Density functional theory (DFT) calculations were used to explore the electronic properties of untreated and plasma‐treated HAp (T‐HAp). MD simulations using the PCFF force field were used to investigate the interactions of HAp/chitosan and T‐HAp/chitosan bionanocomposites. According to the results from thermal gravimetric analysis (TGA), the duration of HAp NP plasma treatment is a significant factor in the weight loss properties for the resultant HAp/chitosan bionanocomposites. The overall reflectance % properties of films prepared with T‐HAp NP samples decreased, confirming the potential applications for skin tissue protection against solar UV radiation. The bioactivity of the bionanocomposite films was also studied by examining the HAp formation by incubating in simulated body fluid.

AbstractThis work aims to design and develop a simple but effective strategy for the selective and sensitive detection of glutathione (GSH) in aqueous medium by exploiting fluorescent bimetallic nanoparticles. To achieve this, water‐soluble, fluorescent silver‐capped gold nanoparticles (F−AgAu) has been synthesized and characterized through conventional methods. The sensing behaviour of the F−AgAu for several analytes of interest has been investigated by employing steady state and time‐resolved spectroscopic techniques. Signaling strategy has been conceptualized by exploiting both “turn‐on” and “turn‐off” condition of the fluorescent nanoparticles against specific analytes in sequential manner. The method is based on the F−AgAu/Hg2+ system, where the initial fluorescence from F−AgAu is quenched (“turn‐off”) by Hg2+. Time‐resolved fluorescence studies have revealed that a photoinduced electron transfer (PET) process from nanoparticle to Hg2+ is primarily responsible for the fluorescence quenching behavior. Interestingly, in the presence of GSH, the fluorescence of the nanoparticle is found to be recovered (“on” state). The fluorescence “on” state of the nanoparticles is attributed to the competitive affinity of Hg2+ for thesurface ligand, GSH. More interestingly, it has been demonstrated that the present signaling strategy is quite effective in detecting GSH in various fruits and food samples at low concentration levels.

The simultaneous detection and effective identification of various sulfur‐containing metal salts (SCMs) is essential for food safety and public health, but it continues to pose significant challenges. In this study, we introduced an innovative iron‐based single‐atom nanozyme (Fe‐N/C) sensor array. This sensor array integrates both colorimetric and photothermal dual modes and is aimed at accurately distinguishing various SCMs. Fe‐N/C catalyst is capable of facilitating the conversion of 3,3',5,5'‐tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) by activating O2, which can turn the colorimetric signal into a photothermal signal under external infrared laser irradiation, allowing for the quantitative detection of SCMs. By leveraging this dual‐mode detection technology, the detection range for SCMs extends from 5 to 150 µM. The limits of detection (LODs) are 0.688‐0.887 µM for the colorimetric method and 0.011‐8.5 µM for the photothermal method. Different SCMs can suppress oxTMB to varying extents, generating distinct colorimetric and photothermal dual‐mode response changes on the sensor array, successfully identifying five types of SCMs. Additionally, it has been utilized for detecting and distinguishing real food samples, including grape wine, pure milk, and raw egg. This innovative design offers new ideas and methods for efficient detection.

The internal quantum efficiency of organic light‐emitting diodes (OLEDs) has approached nearly 100%, making further enhancements in their external quantum efficiency crucial for improving their performance. Traditionally, achieving high outcoupling efficiency has relied on external optical elements, which increase manufacturing costs. This paper presents a novel approach of sandwiching a silver film between silver oxide and N,N'‐di(naphthalene‐1‐yl)‐N,N'‐diphenyl‐benzidine (NPB) films on a glass substrate to form a glass/silver oxide/silver/NPB system designed to enhance anti‐reflective (AR) properties to improve the performance of green OLEDs. Experimental investigations revealed that incorporating 2 nm thick silver oxide (Ag2O) layer between the glass substrate and silver film results in a notable increase in the light transmittance of the electrode from 18 to 40%. This enhancement is attributed to the formation of a silver film with conical surface structures, which reduce reflection and improve light coupling. The application of an AR NPB layer on the silver surface further increases the transmittance to ~70%, demonstrating the effectiveness of the double anti‐reflective coating. The devices with the Ag₂O/Ag electrode exhibited significant performance improvements, achieving a maximum luminance of 9573Cd/m², which is approximately 75.3‐fold higher than the plain Ag electrode and current efficiency of the Ag₂O/Ag device reached 4.26 Cd/A.

Recently, halide perovskites have sparked significant research interest as novel phosphor materials for white light‐emitting diodes (WLEDs) due to their high photoluminescence efficiency, adjustable fluorescence properties, and straightforward fabrication processes. Efforts have also been directed towards simplifying WLED fabrication through the development of single‐component white‐emitting phosphors, with certain halide perovskites proving suitable for this purpose. This review specifically focuses on various design approaches and emission mechanisms of white photoluminescent colloidal halide perovskite nanocrystals (CHPN) and their derivatives, irrespective of dimensional and materials types of perovskite. We compare three distinct sources of white light: narrow band edge free excitonic emission, dopant emission, and other broad‐band emissions. The review supplements the potential of CHPN as single phosphors for WLEDs, highlighting their role in achieving cost‐effective and environment friendly lighting solutions. Recent advancements and associated limitations of WLED fabricated with white‐emitting CHPN are thoroughly assessed. Finally, we outline current challenges and propose future research directions aimed at achieving high‐quality CHPN with white photoluminescence that meets commercial standards.

AbstractThis study investigates the photothermal properties of citrate‐capped gold nanoparticles (Au NPs) dispersed in agarose gel, examining various sizes and concentrations, particularly within a low‐concentration range (0.2–2.5 nM). Heat transfer measurements are conducted on Au NP hydrogels using laser‐light induced heating, revealing a size‐ and concentration‐dependent temperature increase compared to the plain agarose gel matrix. Experimental data, combined with finite‐element analysis, demonstrate that photothermal energy conversion efficiencies are dependent on NP size and concentration, while the thermal conductivity (TC) of all Au NP hydrogels remains constant and independent of these parameters within the tested concentration range. UV‐visible spectroscopy indicates that the observed photothermal heating arises from light absorption and scattering within the Au NP hydrogels. This work highlights the interplay between plasmonic Au NPs of varying sizes and hydrogels as host matrices, significantly impacting photothermal energy conversion properties. The findings herein aim to provide valuable insights for advancements in biomedical and energy‐related applications.

AbstractSilicon oxide (SiOx), due to its significant reversible capacity and significantly reduced volume expansion compared to pure silicon, holds promise as a candidate for high‐performance lithium‐ion battery anode materials. Unfortunately, SiOx still faces challenges for commercialization due to its volume expansion exceeding 160 %, low initial coulombic efficiency, and low electrical conductivity. In this study, we employed metal oxides containing Ti and Sn to dope SiOx/C materials, utilizing a sol‐gel method to prepare SiOx/TiO2/SnO2/C composite anode materials. Furthermore, we adjusted the doping ratios of Sn and Ti to explore the optimal amount for improving the electrochemical performance of the material. Ultimately, it was found that the SiOx/TiO2/SnO2/C composite material prepared with a molar ratio of silicon, titanium, and tin at 10 : 0.7 : 0.3 exhibited the best performance, achieving an initial discharge capacity of 1845.33 mAh ⋅ g−1 at a current density of 100 mA ⋅ g−1 and maintaining a reversible capacity of 843.41 mAh ⋅ g−1 after 100 cycles, with a capacity retention rate of 75.9 %. This work provides a relatively simple method to composite Ti and Sn metal oxides with SiOx, introducing additional conductive pathways to enhance the material‘s conductivity.

AbstractWe present a sustainable green synthesis approach for zinc oxide nanoparticles (ZnO NPs) utilizing Citrus hystrix leaf extract and their application as an active medium in a thin film transistor (TFT)‐based ammonia gas sensor. For the first time, ZnO NPs derived from Citrus hystrix serve as a receptor layer in a thin film transistor (TFT) device, enabling selective ammonia detection at a significantly reduced initiation temperature. The synthesized ZnO NPs, with a wurtzite structure and an average crystallite size of approximately 14 nm, are deposited onto the TFT sensor without the need for an external conducting layer. The sensor demonstrates excellent sensitivity and selectivity, achieving a maximum response of ~85 % at 20 ppm, with a rapid response time of about 10 seconds at room temperature. Notably, the TFT device exhibits an electron mobility of ~10.2 cm2/V ⋅ s and a high on/off ratio (>10⁴) at room temperature. The sensing mechanism is attributed to the oxidation‐reduction interactions between surface‐adsorbed oxygen and NH₃ molecules on the ZnO NPs, which modulate the device's electrical conductivity. This work underscores the importance of eco‐friendly fabrication of high‐performance, durable devices, addressing contemporary environmental and economic concerns.

AbstractCalcium alginate hydrogel beads are spherical polymeric particles with highly crosslinked network structures, known for their excellent monodispersity and retention capabilities. These beads, produced by high‐throughput droplet‐based microfluidic techniques, are widely used for encapsulating and cultivating various microscopic particles such as cells. While internal gelation has been commonly utilized for crosslinking of calcium alginate hydrogel beads in microalgae encapsulation, the use of external gelation remains underexplored. This study utilized droplet‐based microfluidic technology combined with external gelation to produce calcium alginate hydrogel beads for encapsulating the microalgal strain Chlorella vulgaris. Emulsions containing emulsified calcium ions served as the crosslinking phase. Initial geometrical analysis indicated that beads crosslinked with a high concentration of calcium ions (1 g/mL) achieve superior size uniformity and shape consistency. Microalgae cultivation experiments using these beads demonstrated steady growth of Chlorella vulgaris over a 5‐day period, with the beads maintaining their geometric stability until the final day when minor cell leakage was observed. These results provide a foundation for future molecular‐level studies on microalgae cultivation in hydrogel beads and suggest potential applications in fields requiring precisely controlled microalgae growth.