Oxygen Functional Groups Research Articles

Mn-Fe Dual-Metal Assemblages on Carbon-Coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism.

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon-coated aluminum oxide carrier (C-Al2O3) and reinforced it with Mn-Fe bimetal assemblages to prepare a high-performance catalyst Mn-Fe/C-Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ-Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn-Fe/C-Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p-nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical ( ⋅ OH and ⋅ O2 ⋅ ) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn-Fe/C-Al2O3 revealed that it was a cost-competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high-performance and cost-competitive ozone catalyst for prospective application.

Mechanistic effects of graphitization and oxygen functional groups on benzene competitive adsorption of porous carbon under high humidity conditions

Porous carbon is an ideal adsorbent for the elimination of volatile organic compounds (VOCs) attributed to their price, availability and excellent adsorption capacity. However, there are significant variation in the adsorption capacity and adsorption selectivity of different precursors for VOCs under humid conditions after modification because of the differences in their own structural properties. In this study, graphitized hydrophobic porous carbon with excellent specific surface area was successfully synthesized by selecting bamboo fiber, maize, coconut husk and coal as precursors and potassium hydroxide as an activator. Among them, the dynamic adsorption capacity of benzene in the sample with bamboo fiber as precursor was maintained at 74.7% under the high humidity condition (RH90%) compared with the dry state (RH0%). Grand Canonical Monte Carlo (GCMC) simulations and weak interaction force analyses showed that enhanced dispersion attraction between graphitized carbon surfaces and benzene molecules in comparison to disordered carbon surfaces. The existence of oxygen functional groups enhanced the interaction between porous carbon and water through hydrogen bonding leading to preferential adsorption of water molecules, which resulting in the decrease of their adsorption performance in wet condition. This research provided theoretical and experimental views of the effects of graphitization and oxygen functional groups on the competitive adsorption capture of benzene and water by porous carbon, which further provided a reliable approach to synthesizing porous carbon with high adsorption capture for benzene removal in high humidity environments.

Exploring the adsorption of Catechol and Resorcinol onto Croton caudatus activated carbon: An integrated experimental and theoretical approach

The present work aimed to examine the process for adsorption of Catechol (CT) and Resorcinol (RS) onto activated carbon that was obtained from Croton caudatus biomass (CAB). Using a batch method, the maximum removal efficiencies of 99.23 % for CT and 98.68 % for RS was achieved at adsorbent dosage-0.2 g L-1, reaction time-60 min; concentration-100 mgL-1 CT and 80 mgL-1 RS; and pH 6.0 CT and pH 4.0 RS, respectively. A maximum equilibrium adsorption of 56.05 mgg-1 and 61.85 mgg-1 was achieved at pH 6.0 and pH 4.0 for CT and RS. The adsorption behavior of both adsorbates on activated carbon were best described by the Langmuir model (correlation coefficients (R2) = 0.996 for CT and 0.995 for RS) and the pseudo-second order kinetic model. The values of ΔG, ΔS, and ΔH suggest that the adsorption process is spontaneous and endothermic. Additionally, the adsorption process is easily reversible, enabling the reuse of the adsorbate even after fifth cycle. Further, density functional theory (DFT) simulations demonstrated that the CT and RS adsorption onto the AC adsorbent is favorable. Among the oxygen functional groups analysed, the carboxyl group showed the greatest effect on the adsorption process, exhibiting the most negative adsorption energy at -44.869 (CT) and -45.082 kJmol-1 (RS), respectively. Therefore, the activated carbon derived from CAB has significant potential for effectively removing phenolic contaminants from wastewater.

Flexible and highly selective NO2 gas sensor based on direct-ink-writing of eco-friendly graphene oxide for smart wearable application

Nitrogen dioxide (NO2) is a major cause of respiratory disorders in outdoor and indoor environments. Real-time NO2 monitoring using nonintrusive wearable devices can save lives and provide valuable health data. This study reports a room-temperature, wearable, and flexible smart NO2 gas sensor fabricated via cost-effective printing technology on a polyimide substrate. The sensor uses alkali lignin with edge-oxidised graphene oxide (EGO-AL) ink, demonstrating a sensitivity of 1.70% ppm⁻1 and a detection limit of 12.70 ppb, with excellent selectivity towards NO2. The high sensing properties are attributed to labile oxygen functional groups from GO and alkali lignin, offering abundant interacting sites for NO2 adsorption and electron transfer. The sensor fully recovers to the baseline after heat treatment at 150 °C, indicating its reusability. Integration into lab coats showcased its wearable application, utilising a flexible printed circuit board to wirelessly alert the wearer via cell phone to harmful NO2 levels (>3 ppm) in the environment. This smart sensing application underscores the potential for practical, real-time air quality monitoring, personal safety enhancement, and health management.

Dual-emissive carbon dots with high-color purity from sweet basil leaves: synthesis, characterization and optical properties

Abstract In this study, we synthesized dual-emission carbon dots (CDs) from sweet basil leaves dissolved in hexane using the hydrothermal method. Extensive analyses were carried out on their morphology, structure, and optical properties. The CDs show a spherical shape and highly disordered structure with an average diameter of 2 nm. They predominantly comprise carbon surrounded by a dense shell layer of oxygen and nitrogen-related functional groups. Under excitation at a single wavelength of 380 nm, the CDs emit two distinct peaks at 450 and 675 nm demonstrating a narrow bandwidth emission with full width at half maximum (FWHM) of 72 and 27 nm, respectively. The emission characteristics of the CDs are ascribed to the combined effects of radiative recombination of the carbon-core and fully passivated surface states, resulting in two distinct emission peaks and excitation-independent emission property. We present a highly effective and eco-friendly approach approach to fabricate luminescent CDs exhibiting dual emission properties derived from sustainable resources, holding promise for utilization in bioimaging.

Enhancing biochar production: A technical analysis of the combined influence of chemical activation (KOH and NaOH) and pyrolysis atmospheres (N2/CO2) on yields and properties of rice husk-derived biochar

The production of biochar from biomass has received considerable interest due to its potential in environmental applications; however, optimizing biochar properties remains a major challenge. The objective of the present study was to investigate the synergistic effects of pyrolysis atmospheres (N2 and CO2) and chemical activation (pre- and post-pyrolysis) with NaOH and KOH on the properties of biochar useful for its environmental applications. In this study rice husk and biochar were impregnated with KOH and NaOH before and after pyrolysis, which was carried out at 600 °C under N₂ and CO₂ atmosphere. The pyrolytic yields (biochar, liquid and gas) and detailed characterization of biochar were performed. The results showed that pre-activation with both alkalis under a CO2 atmosphere slightly decreased the biochar yield and carbon contents while increasing oxygen in biochars compared to N2 atmosphere. Alkali pre-activation in the CO2 atmosphere considerably increased the specific surface area and pore volume of biochars compared to the N2 atmosphere, with KOH being more effective than NaOH. The maximum specific surface area (SSA) and pore volume (PV) of biochar obtained were 178.4 m2/g and 0.60 cm3/g for KOH activated biochar under CO2, which were 3.2 times and 30 times higher than the untreated biochar. The post-activation of biochars with both alkalis resulted in moderate improvements in textural properties. Overall, chemical activation under CO2 pyrolysis facilitated a higher level of chemical activation reactions leading to increased formation of oxygen functional groups and contributed to enhanced SSA and PV of the biochar useful for adsorption.

Carbon fiber with superhydrophilic interface as metal-free air electrode for all-solid-state Zn-air batteries

The burgeoning interest in all-solid-state Zn-air batteries as next-generation power sources for portable electronics is conspicuous. A pivotal aspect of their advancement lies in developing cost-effective, metal-free air electrodes with high-activity bifunctional oxygen electrocatalysts. This study introduces a superhydrophilic carbon fiber modified with oxygen functional groups (CF-O), achieved through a straightforward one-step activation treatment. Comparative analyses reveal that the CF-O electrode surpasses pristine CF in oxygen reduction and evolution reaction (OER and ORR) activity due to enhanced active sites and expedited ion transport. Notably, the OER/ORR performance depends on the type and quantity of oxygen functional groups. The optimal CF-O electrode displays an OER overpotential of 365.6 mV at 10 mA cm-2 and an ORR peak potential of 0.683 V. Utilizing the CF-O sample as the air electrode in all-solid-state Zn-air batteries yields an open-circuit voltage of 1.28 V and a peak volume power density of 82.8 mW cm-3. Furthermore, endurance testing reveals a charge/discharge voltage gap of 1.07 V at a current density of 1.0 mA cm-2 after 30 cycles. This facile and economical fabrication approach for metal-free air electrodes holds promise for advancing high-performance metal-air batteries compared to various existing techniques.

Improved electrochemical properties of lithium-ion batteries prepared using oxygen plasma-treated needle coke-based anode materials

High-rate capacities and specific capacities are important indicators for evaluating lithium-ion battery (LIB) anodes. To improve the electrochemical properties of needle coke-based anode materials, oxygen plasma treatment was used. Various analyses were performed to assess the impact of the oxygen plasma treatments on the chemical, structural, and morphological properties of the needle coke samples. The oxygen plasma treatment effectively introduced oxygen functional groups (hydroxyl, ether, carbonyl, and carboxyl groups) without significant structural changes to the needle coke samples, and the O/C ratio increased to 0.23 after the plasma treatment. The synergistic effect of the increased oxygen content and the defects formed on the surface by plasma treatment improved the electrochemical properties of the needle coke-based anodes. The discharge capacity of the oxygen plasma-treated needle coke-based LIBs increased to a maximum of 20.48 %, and the retention rate was 74.51 % at 5 C with respect to 0.1 C. The oxygen plasma-treated needle coke material prepared via a simple method could have an important role in improving the rate capacities and specific capacities of LIBs.

Mechanisms of Cd immobilization in contaminated calcareous soils with different textural classes treated by acid- and base-modified biochars

Acid or base modification of biochars has shown promise for enhancing the immobilization of potentially toxic elements (PTEs) such as cadmium (Cd) in contaminated soils. However, limited information is available on the interaction between soil textural classes and modified biochar application for Cd stabilization in contaminated calcareous soils. Therefore, the objective of the study was to examine the extent of Cd immobilization in contaminated calcareous soils with diverse textural classes, utilizing both acid (HNO3) and alkali (NaOH) modified and unmodified biochars derived from sheep manure and rice husk residues. The modified or unmodified biochars were applied at a rate of 2% (w/w) to Cd-contaminated silty clay loam, loam, and sandy loam soils, followed by a 90-day incubation at field water capacity. Sequential extraction and EDTA-release kinetics studies were used to assess the effect of the treatments on the extent and mechanisms of Cd immobilization. Among the treatments, acid-modified manure biochar was most effective at reducing water soluble and exchangeable Cd fractions (-20.5%), by converting them into metal oxide and organic matter bound fractions. This effectiveness was primarily attributed to the significant increase in surface oxygen functional groups in the acid-modified biochar which could promote Cd complexation. However, the acid-modified manure biochar released more immobilized Cd during EDTA extraction than the base-modified manure biochar, suggesting that EDTA extraction of R-O-Cd complexes was easier than extracting Cd associated with insoluble compounds. This difference was likely due to the acidic pH and lower ash content of the acid-modified biochars compared to the base-modified manure biochars. Additionally, the extent of Cd immobilization was lower in sandy loam soil, highlighting the importance of immobilizing Cd in light-textured soils to prevent its transfer to organisms.

Tailoring glassy carbon electrode surface with FeBiO3 for electrochemical detection of dinitrophenol isomers

ABSTRACT This study presents a simultaneous, rapid, and highly sensitive electrochemical detection of 2,4- and 2,5-dinitrophenol isomers using an iron bismuth oxide (FeBiO3)-modified glassy carbon electrode (GCE). The FeBiO3-modified GCE exhibited superior electrochemical performance over bare GCE, Bi2O3-modified GCE, and Fe2O3-modified GCE, as demonstrated by electrochemical impedance spectroscopy (EIS) with the potassium ferricyanide (Fe(CN6)3-/4-) standard. The synthesised electrocatalyst FeBiO3 exhibited strong absorption both in the visible and UV regions of the spectrum, attributed to band gap transitions and charge transfer transitions linked to its Bi2O3 and Fe2O3 components. The morphology and the structure of the FeBiO3 were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), while Fourier transform infrared spectroscopy (FTIR) was employed to analyse the functional groups attached to the surface of FeBiO3. Cyclic voltammetry (CV) clearly demonstrated an increased current and improved peak resolution for the reduction of 2,4- and 2,5-dinitrophenols at the FeBiO3/GCE, compared to the bare GCE. The mechanism shows that the reduction of 2,4- and 2,5-dinitrophenols occurs through interactions with the surface oxygen functional groups of FeBiO3, resulting in the stepwise reduction of their NO2 groups to hydroxyamino compounds and then to nitrosophenols. Using square wave voltammetry (SWV), the reduction peak currents were significantly improved, enhancing detection sensitivity beyond that reported in previous works. A linear range from 1 µM to 1 mm for the dinitrophenol isomers was established, with detection limits of 0.07 µM for 2,4-dinitrophenol and 0.09 µM for 2,5-dinitrophenol. The FeBiO3/GCE electrode showed interferences with mono-nitrophenols and mono-/di-chlorophenols in solution but maintained excellent long-term stability and reproducibility, allowing it to effectively detect dinitrophenol isomers in drinking water, tap water, and wastewater samples.

Development of a novel bio char for CO2 capture and biogas upgrade: Static and dynamic testing

The optimization of the pyrolysis of the spruce sawdust was conducted based on the yield, textural properties, and static capture capacity of the chars to generate a new micro porous char for biogas upgrade. The nature of the precursor (C: 45.68 %, H: 6.08 %, N: 0.15 %, and 0.34 % ash content) helped to tune the porosity of the char for capturing CO2 from gas streams and biogas. The optimization of the pyrolysis at 700 °C, a heating rate of 10 °C / min and holding time of 1 hour, produced a microporous char with high yield, CO2 capture capacity and CO2/CH4 selectivity. The presence of the oxygen and nitrogen-containing functional groups in the optimum char help in the selective capture of CO2. The static CO2 capture capacity of the optimum char was 1.98 mmol/g at atmospheric pressure and 25 °C (90 % CO2 stream). The CSD (700−10−60) have capture capacity of 1.50 mmol/g (at a feed gas stream of 50 % CO2 and adsorption temperature of 25 °C and 120 kPa) which is equivalent to Norit C and Calgon BPL. Hence, spruce sawdust can be used to produce efficient biochar for biogas upgrade (CO2 capture) owing to high capture capacity and CO2/CH4 selectivity (around 3) and easy regeneration of the biochar for 10 consecutive cycles.

Changes in physical and chemical properties of microplastics by ozonation

This study evaluated the altered properties of microplastics during the ozonation process in water matrices. The selected polymers include low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, polyethylene terephthalate, and polyvinyl chloride. The morphology, contact angle, and chemical composition of the pristine and altered microplastics were characterized using field-emission scanning electron microscopy-energy dispersive spectrometry, contact angle analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy (XPS). Microplastic oxidation can lead to surface abrasion, cracking, and fragmentation. XPS analysis indicated that a C=O double bond (carbonyl group) and carboxylic acid/ester bond (O−C=O) were generated in the ozone process. In addition, all the carbonyl index values increased, implying that the number of oxygen functional groups on the surface of the microplastics increased. The contact angle also decreased, indicating that the hydrophilic portion of the microplastics increased due to oxidation. Microplastics, whose surfaces are roughened owing to oxidation or reduced in size owing to fragmentation, pose a fatal threat to aquatic life. In addition, microplastics with increased oxygen functional groups and hydrophilicity due to oxidation treatment have different adsorption properties. Relatively hydrophilic microplastics adsorb heavy metal cations that can adversely affect ecosystems by acting as heavy metal transport mediators.

Rapid and efficient separation of radioactive cesium ion/other radioactive ions by reduced graphene oxide membrane

Separation of cesium ions from other radioactive ions is of great significance for recycling and utilization of radioactive sources, facilitating the management of highly radioactive liquid waste (HLW), as well as for environmental protection. We achieved a highly selective and efficient separation of binary mixtures of 137Cs/60Co, Cs+/Co2+, Cs+/Ni2+, and Cs+/Zn2+ using amino-hydrothermal reduced graphene oxide membranes. The separation factor for non-radioactive binary mixtures is up to 4290, with a water permeance of 50.8 L m−2 h−1 bar−1. The separation factor for radioactive 137Cs/60Co is 623, which is somewhat underestimated due to the detection limit of the high-purity germanium spectrometer. The rGO membranes has the high water permeance of 72.4 L m−2 h−1 bar−1, with a thickness of ∼300 nm. The rGO membrane achieved effective separation of cesium and cobalt ions over a wide range of cesium-to-cobalt ion concentration ratios, with the best results achieved at a concentration ratio of 100:1 for cesium and cobalt. In addition, the rGO membranes showed outstanding stability. The superior performance is attributed to the amino hydrothermal treatment, which reduced oxygen functional groups and directly inserted nitrogen atoms into the GO lattice, ultimately forming stable narrow nanochannels conducive to the size-sieving effect. The findings show that the rGO membranes have excellent separation performance due to their size-sieving effect, and this work has great potential for rapid and efficient treatment of radioactive liquid waste.

Construction of Chitosan-biochar/ZnO/NiO composites for efficient photocatalytic removal of Congo red and tetracycline

The combination of photocatalyst and biochar is an effective strategy to improve the overall photocatalytic activity, but it is still a challenge to find photocatalyst with excellent photocatalytic activity and biochar with large surface and rich oxygen functional groups. In this study, a novel CS-biochar/ZnO/NiO composite with adsorption-photocatalytic performance was constructed using chitosan as biochar source, and exploited for visible-light-driven photocatalytic degradation of tetracycline (TC) and Congo red (CR). The superior photocatalytic activity of CS-biochar/ZnO/NiO than pristine ZnO, NiO and CS-biochar/ZnO under visible light, and 63 %-CS/ZnO/NiO composite has the best photocatalytic activity. The photodegradation efficiency for CR was 94.5 % within 100 min, and the apparent rate constant (k) was 0.0206 min−1, which is about 1.87 and 3.89 times that ZnO and NiO, respectively. For TC, the photodegradation efficiency was 90 % within 45 min, and k was 0.0377 min−1, which is about 1.74 and 2.86 times that bare NiO and ZnO, respectively, which attribute to the synergistic effect between ZnO/NiO and CS-biochar improved the activity of photocatalysts. This work presents a straightforward approach for improving photocatalytic antibiotic and dye degradation through the construction of bifunctional "hybrid" material, which have great potential for application in the removal of contaminants.

Transport of reduced PBAT microplastics in saturated porous media: Synergistic effects of enhanced surface energy and roughness

Microplastic (MP) pollution presents significant global environmental challenges, exacerbated by reduction aging processes in anoxic environments, thereby increasing environmental risks and potential threats to human health. However, the mechanisms underlying the transport of reduced MPs remain poorly understood. In this study, laboratory-scale column experiments were conducted to investigate the transport behavior of polybutylene adipate terephthalate (PBAT), a common biodegradable MPs, and its reduced products obtained through the aging process mediated by two typical reducing agents, NaBH4 and Na2S, under varying conditions (ionic strength (IS), divalent cations, and low molecular weight organic acids (LMWOAs)). The results indicated that reduction aging improved the hydrophilicity of PBAT by increasing the surface roughness (roughness factor increased from 1.300 to 1.642) and surface energy (from 51.80 to 107.03 mN m−1), thereby increasing the mobility of reduced PBAT (with recovery rate increased from 53.77 % to 63.18 %). Increased IS decreased the mobility of reduced PBAT by decreasing the surface negative charge density. Divalent cations inhibited the mobility of both pristine and reduced PBAT in porous media, with pristine PBAT, containing more oxygen functional groups, exhibiting stronger inhibition. Furthermore, LMWOAs promoted the retention of reduced PBAT in porous media, which was dependent on the type of LMWOAs. This study revealed the alterations in MPs properties caused by reduction aging and their effects on transport mechanisms, offering new insights into the transport behavior and environmental risks of reduced MPs.

In Situ Construction of Crumpled Ti3C2Tx Nanosheets Confined S-Doping Red Phosphorus by Ti-O-P Bonds for LIBs Anode with Enhanced Electrochemical Performance.

Red phosphorus (RP) with a high theoretical specific capacity (2596 mA h g-1) and a moderate lithiation potential (∼0.7 V vs Li+/Li) holds promise as an anode material for lithium-ion batteries (LIBs), which still confronts discernible challenges, including low electrical conductivity, substantial volumetric expansion of 300%, and the shuttle effect induced by soluble lithium polyphosphide (LixPPs). Here, S-NRP@Ti3C2Tx composites were in situ prepared through a phosphorus-amine-based method, wherein S-doped red phosphorus nanoparticles (S-NRP) grew and anchored on the crumpled Ti3C2Tx nanosheets via Ti-O-P bonds, constructing a three-dimensional porous structure which provides fast channels for ion and electron transport and effectively buffers the volume expansion of RP. Interestingly, based on the results of adsorption experiments of polyphosphate and DFT calculation, Ti3C2Tx with abundant oxygen functional groups delivers a strong chemical adsorption effect on LixPPs, thus suppressing the shuttle effect and reducing irreversible capacity loss. Furthermore, S-doping improved the conductivity of red phosphorus nanoparticles, facilitating Li-P redox kinetics. Hence, the S-NRP@Ti3C2Tx anode demonstrates outstanding rate performance (1824 and 1090 mA h g-1 at 0.2 and 4.0 A g-1, respectively) and superior cycling performance (1401 mAh g-1 after 500 cycles at 2.0 A g-1).

One-step microwave-assisted synthesis of metal-free heteroatom-doped carbon catalyst for H2O2 electrosynthesis

This study reports on a one-step conversion of polyaniline into a metal-free heteroatom-doped carbon electrocatalyst through microwave heating. A high surface area carbonaceous structure forms after a total synthesis time of only 140 s, with the presence of nitrogen and oxygen functional groups, as confirmed by thorough spectroscopic analysis. This catalyst exhibits high activity (onset potential of 0.73 V vs. RHE), selectivity (82 %), and stability (over a 7.5-hour test period) for the electrochemical oxygen reduction reaction towards hydrogen peroxide in alkaline media. Microwave synthesis reduces heating time by 29-fold and energy consumption by 77-fold, while producing materials with high electrocatalytic efficiency comparable to those conventionally prepared at 700°C. The microwave and the conventionally synthesized heteroatom-doped carbon catalysts show similar electrochemical performances, which can be attributed to the presence of nearly identical nitrogen functional groups and surface area in the two samples. In contrast, the microwave and conventionally synthesized samples exhibit significant variations in their oxygen functional groups. These results suggest that nitrogen functional groups are the main active sites for alkaline hydrogen peroxide formation, while oxygen functional groups play a minor role in the catalytic activity. Our work brings a solid contribution to the debate regarding the active centers for hydrogen peroxide formation.

Ratiometric Fluorescent Probes for Copper Ion Detection and Cuproptosis Studies

Abstract: This study reviews the latest progress of ratiometric fluorescent probes of copper ions from 2022 till now. As a key trace element in biological systems, copper ions play an important role in a variety of biological processes. However, the abnormal change in copper ion concentration is closely related to a variety of diseases, so the development of highly sensitive and highly selective copper ion detection methods is of great significance for scientific research and clinical diagnosis. In this paper, we first introduced the classification of copper ion fluorescence probes, including molecular sensors based on five-membered azocycles, six-membered azocycles, imide groups (R2C=NR'), oxygen and nitrogen functional groups (such as ethers, aldehydes, ketones, esters, carboxylic acids and hydroxyl groups) and group ⅥA elements. Subsequently, the application of nanosensors in the detection of copper ions is further discussed, especially the nanosensors in which copper is used as a reactant, catalyst or alternative reaction. Finally, the current research status of copper ion fluorescence probes is summarized, and the future development direction is prospected in order to provide reference and inspiration for the design of new high-efficiency copper ion detection tools.

In-situ DRIFTS insights into the evolution of surface functionality of biochar upon thermal air oxidation

Biochar surface functionality is crucial for its application. Herein, the evolution of biochar surface functionality upon thermal air oxidation (TAO) was investigated in-situ by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and thermogravimetric analysis (TGA). The results show that, although the surface functionality of biochar is remarkably changed during TAO at the initial low temperature range, the biochar weight is still stable in the initial low temperature range, suggesting the chemisorption of O2 as intermediate oxygenated functional groups (OFGs) on biochar surface. Moreover, the evolution of biochar surface functionality upon TAO is highly affected on its preparation temperature and intrinsic minerals. Specifically, biochar produced at a high temperature is more resistant to TAO, and more favorable for the formation of ketone groups during TAO. While the biochars prepared at low or medium temperatures show a remarkable formation of carboxyl/lactone groups upon TAO, and the maximum temperature for the formation of carboxyl/lactone groups can be achieved at 400 °C. It's worth noting that the intrinsic minerals in biochar catalyze the TAO reaction, resulting in a much higher mass loss of biochar upon TAO. Furthermore, with the catalysis of intrinsic minerals, TAO is more suitable for enhancing the performance of biochar with intrinsic minerals. These results facilitate the design of engineered biochar via TAO for enhanced applications.

Regulation of surface oxygen functional groups in starch-derived hard carbon via pre-oxidation: A strategy for enhanced sodium storage performance

During the process of sodium storage in hard carbon anodes, the significance of surface oxygen functional groups cannot be overlooked. In this work, we utilize starch as raw material to synthesize hard carbon by the process of pre-oxidation and two-step carbonization. XPS analysis reveals that pre-oxidation bolsters the presence of CO bonds, thereby providing more active sites. TEM analysis reveals that hard carbon with pseudo-graphite and graphite-like structure is obtained at relatively high carbonization temperature (1400 °C), and the formation of closed pores results in lower specific surface area. The introduction of appropriate oxygen-containing groups in pre-oxidation process can facilitate the cross-linking of starch chains, promoting the increase of defect sites and the sodium storage performance of hard carbon. A series of samples are prepared at various pre-oxidation temperature. Among them, P200-HC obtained after pre-oxidation at 200 °C and carbonization at 1400 °C exhibits the highest reversible specific capacity of 342.7 mAh g−1 at current density of 0.1 C with an initial Coulombic efficiency of 71.1 %, and capacity retention of 87.3 % at current density of 1 C. The work presents a viable approach for the synthesis of hard carbon derived from starch, thereby expanding the design tactic of sodium-ion batteries with improved performance.