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2022 Volume 38 Issue 12
2022, 38(12): 210804
doi: 10.3866/PKU.WHXB202108041
Abstract:
Compared to traditional sensor device arrays, optical fiber systems capable of wide-range detection are gradually emerging as strong candidates for distributed monitoring owing to their simplified structure. However, the working mechanism of optical fiber sensors limits their use to the detection of physical parameters such as refractive index and is an obstacle for the detection of small doses of molecules by optical fiber systems. Several researchers have focused on this aspect to endow sensitivity to these optical fibers for gas or liquid molecules. By deliberately destroying the fiber structure, strong interactions between the evanescent field of optical fibers and the target materials, such as microfibers, D-shaped fiber, etc. can be achieved. Assisted by the surface plasmon resonance techniques, such configurations can exhibit highly enhanced sensitivity to a change in the refractive index caused by gas or liquid molecules. Two-dimensional materials are an excellent candidate as coating materials due to their high specific surface area, which also guarantees a large sensing response and simultaneously minimizes any side effects by suppressing the propagating mode of optical fibers. However, owing to the obstacles in optical fiber engineering and device fabrication, the abovementioned functional 2D sensors are still limited to sample-scale fabrication, and their mass-production has not yet been realized. An all-fiber distributed sensing system with high single-spot sensitivity is still difficult to fabricate. Here, we propose a new configuration of a grid-distributed environmental optical fiber sensing by introducing low-pressure chemical vapor deposition (LPCVD)-grown graphene photonic crystal fiber (PCF) into the optical fiber sensing system. We successfully synthesized monolayer and/or bilayer graphene in the air holes of PCF. By fusing the graphene PCF (Gr-PCF) to a single mode optical fiber, we fabricated an all-optical-fiber sensing system. Preliminary experiments suggest that Gr-PCF can selectively detect NO2 gas at ppb-level and exhibit ionic sensitivity in liquids. The ability to detect NO2 gas is attributed to the graphene layer's interaction among light-mode and adsorbed molecules: adsorption-induced additional hole-doping caused a shift in the Fermi level of graphene and eventually modulated its light absorption, leading to changes in the light intensity signals. We believe that the sensor can be extended to other kinds of gases and liquids, considering the affinity of graphene toward various molecules. In view of practical optical sensors, our design is compatible with the time domain or wavelength domain multiplexing techniques of optical fiber communication systems. Because CVD-based synthesis can be used to realize mass production, the design proposed herein shall be one of the answers to the distributed optical fiber environmental sensors.![]()
Compared to traditional sensor device arrays, optical fiber systems capable of wide-range detection are gradually emerging as strong candidates for distributed monitoring owing to their simplified structure. However, the working mechanism of optical fiber sensors limits their use to the detection of physical parameters such as refractive index and is an obstacle for the detection of small doses of molecules by optical fiber systems. Several researchers have focused on this aspect to endow sensitivity to these optical fibers for gas or liquid molecules. By deliberately destroying the fiber structure, strong interactions between the evanescent field of optical fibers and the target materials, such as microfibers, D-shaped fiber, etc. can be achieved. Assisted by the surface plasmon resonance techniques, such configurations can exhibit highly enhanced sensitivity to a change in the refractive index caused by gas or liquid molecules. Two-dimensional materials are an excellent candidate as coating materials due to their high specific surface area, which also guarantees a large sensing response and simultaneously minimizes any side effects by suppressing the propagating mode of optical fibers. However, owing to the obstacles in optical fiber engineering and device fabrication, the abovementioned functional 2D sensors are still limited to sample-scale fabrication, and their mass-production has not yet been realized. An all-fiber distributed sensing system with high single-spot sensitivity is still difficult to fabricate. Here, we propose a new configuration of a grid-distributed environmental optical fiber sensing by introducing low-pressure chemical vapor deposition (LPCVD)-grown graphene photonic crystal fiber (PCF) into the optical fiber sensing system. We successfully synthesized monolayer and/or bilayer graphene in the air holes of PCF. By fusing the graphene PCF (Gr-PCF) to a single mode optical fiber, we fabricated an all-optical-fiber sensing system. Preliminary experiments suggest that Gr-PCF can selectively detect NO2 gas at ppb-level and exhibit ionic sensitivity in liquids. The ability to detect NO2 gas is attributed to the graphene layer's interaction among light-mode and adsorbed molecules: adsorption-induced additional hole-doping caused a shift in the Fermi level of graphene and eventually modulated its light absorption, leading to changes in the light intensity signals. We believe that the sensor can be extended to other kinds of gases and liquids, considering the affinity of graphene toward various molecules. In view of practical optical sensors, our design is compatible with the time domain or wavelength domain multiplexing techniques of optical fiber communication systems. Because CVD-based synthesis can be used to realize mass production, the design proposed herein shall be one of the answers to the distributed optical fiber environmental sensors.
2022, 38(12): 211103
doi: 10.3866/PKU.WHXB202111030
Abstract:
Carbon quantum dots (CQDs) have attracted extensive interest due to their strong fluorescence as well as inexpensive and plentiful resources for manufacture. There are numerous published reports on the preparation of CQDs and direct applications based on their photoluminescence. Successive chemical modification of CQDs in an appropriate manner might expand the application scope of CQDs and transform them into practical fine chemicals. The various functional groups on the surface of CQDs allow for efficient chemical modification while imparting them with hydrophilicity. Covalent linking of hydrophobic hydrocarbon chains to CQDs would lead to the formation of novel surfactants. Here, a technique for preparing CQD-based cationic surfactants is depicted in detail. This was rare to be reported according to recent publishes. First, a mixture of ethylenediamine tetraacetic acid and ethylenediamine in the presence of hydrogen peroxide in an aqueous medium was pyrolyzed at 180 ℃ for 60 min. The resulting CQDs are represented as OX-CQDs. Then, the OX-CQDs were subjected to quaternization with 1-chlorododecane for obtaining the cationic surfactant (OX-CQDs-C12H25). The OX-CQDs-C12H25 surfactant effectively decreased the surface tension of water from 72.0 to 26.7 mN∙m−1 at the critical micelle concentration of 5.0 mg∙mL−1, thus demonstrating superior performance over several new Gemini cationic surfactants. The OX-CQDs-C12H25 surfactant also decreased the contact angles of water considerably. However, when longer alkyl chains such as －C14H29 or －C16H33 were attached to the CQDs, the corresponding surfactant was less effective in decreasing the surface tension of water. Calculations based on the Gibbs absorption isothermal equation revealed that two more －C12H25 chains were bonded with a carbon quantum dot averagely, implying that the as-prepared CQD-cationic surfactant belonged to the category of Gemini surfactants. Quaternization with 1-chlorododecane also led to a notable enhancement in the antibacterial activity for Escherichia coli as compared with that of unmodified CQDs. The antibacterial percentage approached 100% even the solution was diluted to 0.41 mg∙mL−1, which was much lower than the critical micelle concentration. The fluorescence quantum yield of OX-CQDs-C12H25 reached 6.44%. Experimental results revealed that hydrogen peroxide played a positive role in improving the surface activity and fluorescence quantum yield of OX-CQDs-C12H25. The surface activity, antibiosis, and fluorescence endowed the versatilities of OX-CQDs-C12H25. This novel, economical technique for synthesizing cationic surfactants eliminates the need for introducing hydrophilic groups. The hydrothermal approach for preparing CQDs satisfies the demand for green chemical synthesis. From this aspect, our technique provides efficient access to synthesizing cationic surfactants.![]()
Carbon quantum dots (CQDs) have attracted extensive interest due to their strong fluorescence as well as inexpensive and plentiful resources for manufacture. There are numerous published reports on the preparation of CQDs and direct applications based on their photoluminescence. Successive chemical modification of CQDs in an appropriate manner might expand the application scope of CQDs and transform them into practical fine chemicals. The various functional groups on the surface of CQDs allow for efficient chemical modification while imparting them with hydrophilicity. Covalent linking of hydrophobic hydrocarbon chains to CQDs would lead to the formation of novel surfactants. Here, a technique for preparing CQD-based cationic surfactants is depicted in detail. This was rare to be reported according to recent publishes. First, a mixture of ethylenediamine tetraacetic acid and ethylenediamine in the presence of hydrogen peroxide in an aqueous medium was pyrolyzed at 180 ℃ for 60 min. The resulting CQDs are represented as OX-CQDs. Then, the OX-CQDs were subjected to quaternization with 1-chlorododecane for obtaining the cationic surfactant (OX-CQDs-C12H25). The OX-CQDs-C12H25 surfactant effectively decreased the surface tension of water from 72.0 to 26.7 mN∙m−1 at the critical micelle concentration of 5.0 mg∙mL−1, thus demonstrating superior performance over several new Gemini cationic surfactants. The OX-CQDs-C12H25 surfactant also decreased the contact angles of water considerably. However, when longer alkyl chains such as －C14H29 or －C16H33 were attached to the CQDs, the corresponding surfactant was less effective in decreasing the surface tension of water. Calculations based on the Gibbs absorption isothermal equation revealed that two more －C12H25 chains were bonded with a carbon quantum dot averagely, implying that the as-prepared CQD-cationic surfactant belonged to the category of Gemini surfactants. Quaternization with 1-chlorododecane also led to a notable enhancement in the antibacterial activity for Escherichia coli as compared with that of unmodified CQDs. The antibacterial percentage approached 100% even the solution was diluted to 0.41 mg∙mL−1, which was much lower than the critical micelle concentration. The fluorescence quantum yield of OX-CQDs-C12H25 reached 6.44%. Experimental results revealed that hydrogen peroxide played a positive role in improving the surface activity and fluorescence quantum yield of OX-CQDs-C12H25. The surface activity, antibiosis, and fluorescence endowed the versatilities of OX-CQDs-C12H25. This novel, economical technique for synthesizing cationic surfactants eliminates the need for introducing hydrophilic groups. The hydrothermal approach for preparing CQDs satisfies the demand for green chemical synthesis. From this aspect, our technique provides efficient access to synthesizing cationic surfactants.
2022, 38(12): 220103
doi: 10.3866/PKU.WHXB202201037
Abstract:
Morphology regulation and the improvement of carrier separation efficiency are important strategies for the preparation of photocatalysts with excellent performance. MoSx with a three-dimensional (3D) nanoflower morphology formed by nanosheet stacking was prepared by a simple hydrothermal method, and MoSx/In2O3 with good hydrogen evolution activity was obtained by coupling with In2O3. The preparation of the three-dimensional nanoflower morphology combined with the construction of an S-scheme heterojunction improves the electron accumulation at the active site for hydrogen evolution reaction. The UV diffuse reflection test showed that the issue of poor light absorption of In2O3 was improved. The rapid separation and transfer of electrons were effectively confirmed by characterization methods such as fluorescence spectroscopy and electrochemical tests. The most intuitively manifestation of the performance improvement of the composite material is that the optimal hydrogen evolution rate reached 6704.2 μmol∙g−1∙h−1, which is 1.8 times that of pure MoSx. Therefore, in this study, a new idea for the development of molybdenum-based sulfides for photocatalytic hydrogen production is provided.![]()
Morphology regulation and the improvement of carrier separation efficiency are important strategies for the preparation of photocatalysts with excellent performance. MoSx with a three-dimensional (3D) nanoflower morphology formed by nanosheet stacking was prepared by a simple hydrothermal method, and MoSx/In2O3 with good hydrogen evolution activity was obtained by coupling with In2O3. The preparation of the three-dimensional nanoflower morphology combined with the construction of an S-scheme heterojunction improves the electron accumulation at the active site for hydrogen evolution reaction. The UV diffuse reflection test showed that the issue of poor light absorption of In2O3 was improved. The rapid separation and transfer of electrons were effectively confirmed by characterization methods such as fluorescence spectroscopy and electrochemical tests. The most intuitively manifestation of the performance improvement of the composite material is that the optimal hydrogen evolution rate reached 6704.2 μmol∙g−1∙h−1, which is 1.8 times that of pure MoSx. Therefore, in this study, a new idea for the development of molybdenum-based sulfides for photocatalytic hydrogen production is provided.
2022, 38(12): 220105
doi: 10.3866/PKU.WHXB202201050
Abstract:
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) is considered one of the most environment friendly, economical, and efficient methods for synthesizing 2,5-furandicarboxylic acid (FDCA), which is a promising bio-based precursor of polyethylene 2,5-furandicarboxylate. In this study, we synthesized PtRuAgCoNi high-entropy alloy nanoparticles, with an average diameter of approximately 9 nm, using a solvothermal method. The synthesized nanoparticles displayed a core-shell microstructure, in which Co, Ru, Ag, and Ni were distributed over the entire core-shell microstructure of each nanoparticle, while Pt was mainly concentrated in the shell structure. A two-step method, including small-molecule substitution and low-temperature calcination, was used to remove the surfactant from the synthesized nanoparticles without changing the structure and composition of the nanoparticles. After being deposited on a carbon support, the high-entropy alloy nanoparticles, with or without surfactants, exhibited better catalytic performance in the electrocatalytic oxidation of HMF to FDCA than the commercial Pt/C catalyst. The removal of surfactants after calcination at 185 ℃ can further improve electrocatalytic performance, suggesting promising application prospects of high-entropy alloy nanoparticles in electrocatalysis and green chemistry.![]()
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) is considered one of the most environment friendly, economical, and efficient methods for synthesizing 2,5-furandicarboxylic acid (FDCA), which is a promising bio-based precursor of polyethylene 2,5-furandicarboxylate. In this study, we synthesized PtRuAgCoNi high-entropy alloy nanoparticles, with an average diameter of approximately 9 nm, using a solvothermal method. The synthesized nanoparticles displayed a core-shell microstructure, in which Co, Ru, Ag, and Ni were distributed over the entire core-shell microstructure of each nanoparticle, while Pt was mainly concentrated in the shell structure. A two-step method, including small-molecule substitution and low-temperature calcination, was used to remove the surfactant from the synthesized nanoparticles without changing the structure and composition of the nanoparticles. After being deposited on a carbon support, the high-entropy alloy nanoparticles, with or without surfactants, exhibited better catalytic performance in the electrocatalytic oxidation of HMF to FDCA than the commercial Pt/C catalyst. The removal of surfactants after calcination at 185 ℃ can further improve electrocatalytic performance, suggesting promising application prospects of high-entropy alloy nanoparticles in electrocatalysis and green chemistry.
Citronella Oil Nanoemulsion: Formulation, Characterization, Antibacterial Activity, and Cytotoxicity
2022, 38(12): 220505
doi: 10.3866/PKU.WHXB202205053
Abstract:
The excessive and unreasonable use of synthetic bactericides in the agricultural field has caused many serious problems, including toxic effects on human health and environmental pollution. Therefore, searching for low toxicity, highly efficient, and no-residue natural bactericides is urgently needed. Plant essential oil has become an emerging and hot topic in the agricultural field because of its excellent bactericidal activity, good biocompatibility, and abundant sources. Citronella oil is a natural plant essential oil with insect repellent, insecticidal, and antibacterial activities, which mainly includes citronellal, geraniol, and citronellol. At present, the major of research on citronella oil focuses on the repellency and control of sanitary pests, but there are relatively few reports on the control of agricultural pathogenic bacteria. In addition, the hydrophobicity and volatility of citronella oil lead to its low bioavailability and hinder its full biological activity. Therefore, constructing a delivery system for improving the hydrophobicity and reducing the volatility of citronella oil is urgently needed. Nanoemulsions have the advantages of fine and uniform droplets, better physical stability, efficient permeation ability, and enhanced bioavailability. Therefore, nanoemulsions are important drug delivery systems for hydrophobic pesticides. In this study, the influences of emulsifier type (hydrophilic-lipophilic balance (HLB)), dosage, and emulsifying time on the formation and stability of citronella oil nanoemulsions were investigated by observing the appearances and microstructures of samples and measuring droplet size, thereby the optimized formula of the citronella oil nanoemulsions was determined. Furthermore, the bioactivity and biosafety of citronella oil nanoemulsions were also investigated. The results showed that nanoemulsions using castor oil polyoxyethylene ethers EL-40 (hydrophilic-lipophilic balance = 13.5) as an emulsifier had the best performance, and the stability of nanoemulsions improved as the emulsifier dosage increased from 3% to 7% (w, mass fraction). In addition, the nanoemulsion prepared through high speed shearing for 3 min was the most stable. The optimal formula for citronella oil nanoemulsions was determined to contain 5% (w) citronella oil, 6% (w) emulsifier (EL-40), and 89% (w) deionized water, upon high speed shearing for 3 min. Then, the inhibitory effect of citronella oil nanoemulsions against the growth of Pantoea ananatis was studied. The concentration for 50% of maximal effect (EC50) of citronella oil nanoemulsions against Pantoea ananatis was 74.85 mg·L−1. The cell viability of L02 cells treated with the citronella oil nanoemulsions (below 100 mg·L−1) was above 83% after 24 h, and the apoptosis rate was 6.93%, indicating that the citronella oil nanoemulsions had low cytotoxicity. This research facilitated the design and fabrication of stable, efficient, and safe agricultural nanoemulsions, and it provides a practical solution for using plant essential oils as agricultural bactericides.![]()
The excessive and unreasonable use of synthetic bactericides in the agricultural field has caused many serious problems, including toxic effects on human health and environmental pollution. Therefore, searching for low toxicity, highly efficient, and no-residue natural bactericides is urgently needed. Plant essential oil has become an emerging and hot topic in the agricultural field because of its excellent bactericidal activity, good biocompatibility, and abundant sources. Citronella oil is a natural plant essential oil with insect repellent, insecticidal, and antibacterial activities, which mainly includes citronellal, geraniol, and citronellol. At present, the major of research on citronella oil focuses on the repellency and control of sanitary pests, but there are relatively few reports on the control of agricultural pathogenic bacteria. In addition, the hydrophobicity and volatility of citronella oil lead to its low bioavailability and hinder its full biological activity. Therefore, constructing a delivery system for improving the hydrophobicity and reducing the volatility of citronella oil is urgently needed. Nanoemulsions have the advantages of fine and uniform droplets, better physical stability, efficient permeation ability, and enhanced bioavailability. Therefore, nanoemulsions are important drug delivery systems for hydrophobic pesticides. In this study, the influences of emulsifier type (hydrophilic-lipophilic balance (HLB)), dosage, and emulsifying time on the formation and stability of citronella oil nanoemulsions were investigated by observing the appearances and microstructures of samples and measuring droplet size, thereby the optimized formula of the citronella oil nanoemulsions was determined. Furthermore, the bioactivity and biosafety of citronella oil nanoemulsions were also investigated. The results showed that nanoemulsions using castor oil polyoxyethylene ethers EL-40 (hydrophilic-lipophilic balance = 13.5) as an emulsifier had the best performance, and the stability of nanoemulsions improved as the emulsifier dosage increased from 3% to 7% (w, mass fraction). In addition, the nanoemulsion prepared through high speed shearing for 3 min was the most stable. The optimal formula for citronella oil nanoemulsions was determined to contain 5% (w) citronella oil, 6% (w) emulsifier (EL-40), and 89% (w) deionized water, upon high speed shearing for 3 min. Then, the inhibitory effect of citronella oil nanoemulsions against the growth of Pantoea ananatis was studied. The concentration for 50% of maximal effect (EC50) of citronella oil nanoemulsions against Pantoea ananatis was 74.85 mg·L−1. The cell viability of L02 cells treated with the citronella oil nanoemulsions (below 100 mg·L−1) was above 83% after 24 h, and the apoptosis rate was 6.93%, indicating that the citronella oil nanoemulsions had low cytotoxicity. This research facilitated the design and fabrication of stable, efficient, and safe agricultural nanoemulsions, and it provides a practical solution for using plant essential oils as agricultural bactericides.
2022, 38(12): 220700
doi: 10.3866/PKU.WHXB202207006
Abstract:
Pesticide droplet deposition on targeted plant leaf surfaces is of great importance but remains a significant challenge, especially on leaf surfaces of superhydrophobic plants. The loss of sprayed pesticide droplets leads to the overuse of pesticides and environmental pollution. Therefore, in this study, we aimed at developing a system that was capable of enhancing droplet deposition on the surfaces of superhydrophobic plant leaves via hydrogen bonding between a bio-based surfactant and glycerol at low concentration (0.25%). The system based on the sorbitol-alkylamine surfactant (denoted as SSAS-C12) with a small amount of glycerol (0.001%) could efficiently inhibit droplet bouncing and splashing on different superhydrophobic/hydrophobic plant leaf surfaces. The results obtained indicated that the addition of glycerol did not change the surface tension, viscosity, contact angles on the plant leaf surfaces, and aggregate morphology of the SSAS-C12 solutions. Diffusion-ordered nuclear magnetic resonance spectroscopy revealed that glycerol accelerated the diffusion of SSAS-C12 molecules. More specifically, SSAS-C12 molecules could diffuse and adsorb on plant leaf surfaces within a short period of time. Other surfactants (denoted as DSSAS-C12 and BAPO-C12) with varying numbers of hydroxyl groups were used to verify the enhancement of the deposition on superhydrophobic plant leaf surfaces caused by hydrogen bonding. It was revealed that a decrease in the number of hydroxyl groups in the surfactant molecules led to a decrease in the number of hydrogen bonds between the glycerol and surfactant molecules. Moreover, the diffusion rates of the DSSAS-C12 and BAPO-C12 molecules in solution were low, causing the surfactant molecules to not reach the solid-liquid interface in time. Consequently, the droplets containing surfactant molecules (of DSSAS-C12 or BAPO-C12) bounced and broke up on the surfaces of plant leaves. Finally, we used molecular dynamics (MD) simulations to explore the energy and molecular distribution of different surfactant-glycerol mixtures. The energy evolution of the SSAS-C12-glycerol system and the distribution of surfactant molecules relative to the distance from the solid surface in the MD simulations showed that the addition of glycerol twisted the headgroup in SSAS-C12 via hydrogen bonding with glycerol. In this case, SSAS-C12 molecules experienced rapid diffusion and adsorption on the solid interface. Therefore, this study not only provided a constructive way to overcome the bouncing behavior of droplets but also prompted us to verify whether all hydrogen bonding interactions among different molecules could display similar control efficiencies through the rational selection of additives. ![]()
Pesticide droplet deposition on targeted plant leaf surfaces is of great importance but remains a significant challenge, especially on leaf surfaces of superhydrophobic plants. The loss of sprayed pesticide droplets leads to the overuse of pesticides and environmental pollution. Therefore, in this study, we aimed at developing a system that was capable of enhancing droplet deposition on the surfaces of superhydrophobic plant leaves via hydrogen bonding between a bio-based surfactant and glycerol at low concentration (0.25%). The system based on the sorbitol-alkylamine surfactant (denoted as SSAS-C12) with a small amount of glycerol (0.001%) could efficiently inhibit droplet bouncing and splashing on different superhydrophobic/hydrophobic plant leaf surfaces. The results obtained indicated that the addition of glycerol did not change the surface tension, viscosity, contact angles on the plant leaf surfaces, and aggregate morphology of the SSAS-C12 solutions. Diffusion-ordered nuclear magnetic resonance spectroscopy revealed that glycerol accelerated the diffusion of SSAS-C12 molecules. More specifically, SSAS-C12 molecules could diffuse and adsorb on plant leaf surfaces within a short period of time. Other surfactants (denoted as DSSAS-C12 and BAPO-C12) with varying numbers of hydroxyl groups were used to verify the enhancement of the deposition on superhydrophobic plant leaf surfaces caused by hydrogen bonding. It was revealed that a decrease in the number of hydroxyl groups in the surfactant molecules led to a decrease in the number of hydrogen bonds between the glycerol and surfactant molecules. Moreover, the diffusion rates of the DSSAS-C12 and BAPO-C12 molecules in solution were low, causing the surfactant molecules to not reach the solid-liquid interface in time. Consequently, the droplets containing surfactant molecules (of DSSAS-C12 or BAPO-C12) bounced and broke up on the surfaces of plant leaves. Finally, we used molecular dynamics (MD) simulations to explore the energy and molecular distribution of different surfactant-glycerol mixtures. The energy evolution of the SSAS-C12-glycerol system and the distribution of surfactant molecules relative to the distance from the solid surface in the MD simulations showed that the addition of glycerol twisted the headgroup in SSAS-C12 via hydrogen bonding with glycerol. In this case, SSAS-C12 molecules experienced rapid diffusion and adsorption on the solid interface. Therefore, this study not only provided a constructive way to overcome the bouncing behavior of droplets but also prompted us to verify whether all hydrogen bonding interactions among different molecules could display similar control efficiencies through the rational selection of additives.
2022, 38(12): 220405
doi: 10.3866/PKU.WHXB202204052
Abstract:
In recent years, colloidal quantum wells (CQWs), also known as semiconductor nanoplatelets, have become the new kind of promising optoelectronic material because of their excellent optoelectronic properties, such as high color purity, high photoluminescence quantum efficiency, and adjustable color emissions. As a significant application of CQWs, light-emitting diodes based on CQWs (or CQW-LEDs) possess a number of advantages, such as an extremely narrow spectrum, excellent color purity, high efficiency, solution-processed fabrication, and good compatibility with flexible electronics. CQW-LEDs demonstrate an important application prospect in the fields of next-generation display and solid-state lighting, and therefore, attract significant attention from academic and industrial settings. In this review, some basic concepts of CQW-LEDs are first introduced (e.g., the design of CQW materials, employment of device structures, and understanding of emission mechanisms), which are expected to help with understanding this new type of LEDs. Thereafter, from the perspective of CQW emitting material types, the recent research progress in the development of CQW-LEDs based on core-only CQWs, core/crown CQWs, core/shell CQWs, complex-heterojunction-based CQWs, and impurity-doped CQWs is presented. The properties of various CQWs are also compared. In this section, by combining the recent work from our research group, the design strategies of high-performance CQW-LEDs are discussed in detail, including the analyses of material selection, device structure, working mechanism, and luminescence process. In the next section, the integrated applications of CQW-LEDs are illustrated, such as their use in LiFi-type communication, furthermore, their preparation as flexible optoelectronic materials is also reported. Finally, the present challenges (e.g., low efficiencies, short lifetimes, sub-optimal device engineering, and a narrow emission color region) and future development opportunities (e.g., flexible displays, flexible lighting, and CQW-LEDs with low-cost printing fabrication processes) of CQW-LEDs are discussed. Although the performance of CQW-LEDs still lags behind other kinds of state-of-the-art soft-material-based LEDs (e.g., organic LEDs, colloidal quantum dot LEDs, and perovskite LEDs), it has been gradually enhanced in the last eight years. Upon overcoming the current challenges, the prospect for the mass production of CQW-LEDs will be undoubtedly feasible. Thus, this review is not only an important reference that discusses the evolution of CQW-LEDs, it also provides insightful ideas for the development of materials for other optoelectronic applications (e.g., solar cells, lasers, photodetectors, sensors, X-ray imaging, and light communication).![]()
In recent years, colloidal quantum wells (CQWs), also known as semiconductor nanoplatelets, have become the new kind of promising optoelectronic material because of their excellent optoelectronic properties, such as high color purity, high photoluminescence quantum efficiency, and adjustable color emissions. As a significant application of CQWs, light-emitting diodes based on CQWs (or CQW-LEDs) possess a number of advantages, such as an extremely narrow spectrum, excellent color purity, high efficiency, solution-processed fabrication, and good compatibility with flexible electronics. CQW-LEDs demonstrate an important application prospect in the fields of next-generation display and solid-state lighting, and therefore, attract significant attention from academic and industrial settings. In this review, some basic concepts of CQW-LEDs are first introduced (e.g., the design of CQW materials, employment of device structures, and understanding of emission mechanisms), which are expected to help with understanding this new type of LEDs. Thereafter, from the perspective of CQW emitting material types, the recent research progress in the development of CQW-LEDs based on core-only CQWs, core/crown CQWs, core/shell CQWs, complex-heterojunction-based CQWs, and impurity-doped CQWs is presented. The properties of various CQWs are also compared. In this section, by combining the recent work from our research group, the design strategies of high-performance CQW-LEDs are discussed in detail, including the analyses of material selection, device structure, working mechanism, and luminescence process. In the next section, the integrated applications of CQW-LEDs are illustrated, such as their use in LiFi-type communication, furthermore, their preparation as flexible optoelectronic materials is also reported. Finally, the present challenges (e.g., low efficiencies, short lifetimes, sub-optimal device engineering, and a narrow emission color region) and future development opportunities (e.g., flexible displays, flexible lighting, and CQW-LEDs with low-cost printing fabrication processes) of CQW-LEDs are discussed. Although the performance of CQW-LEDs still lags behind other kinds of state-of-the-art soft-material-based LEDs (e.g., organic LEDs, colloidal quantum dot LEDs, and perovskite LEDs), it has been gradually enhanced in the last eight years. Upon overcoming the current challenges, the prospect for the mass production of CQW-LEDs will be undoubtedly feasible. Thus, this review is not only an important reference that discusses the evolution of CQW-LEDs, it also provides insightful ideas for the development of materials for other optoelectronic applications (e.g., solar cells, lasers, photodetectors, sensors, X-ray imaging, and light communication).
2022, 38(12): 220800
doi: 10.3866/PKU.WHXB202208008
Abstract:
The storage and utilization of energy is one of the important topics in the development of science and technology, especially regarding secondary batteries, which are efficient electrical-/chemical-energy-converting devices. This review systematically introduces the important research progress made in the context of secondary batteries, starting from their development and leading to the introduction of related basic theoretical knowledge. The current research on secondary batteries that are based on different systems and related key materials is discussed in detail, and includes lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, zinc-ion batteries, calcium-ion batteries, aluminum-ion batteries, fluorine-ion batteries, chloride-ion batteries, dual-ion batteries, lithium-sulfur (Se) batteries, sodium-sulfur (Se) batteries, potassium-sulfur (Se) batteries, polyvalent metal-sulfur-based batteries, lithium-oxygen batteries, sodium-oxygen batteries, potassium-oxygen batteries, aqueous metal-ion batteries, polyvalent metal-oxygen batteries, lithium-bromine (or lithium-iodine) batteries, photo-assisted batteries, flexible batteries, organic batteries, and metal-carbon dioxide batteries. Additionally, the common characterization techniques for electrode reaction processes in battery research are also introduced, including cryo-electron microscopy, transmission electron microscopy, synchrotron radiation, in situ spectroscopic techniques, and magnetic characterization. This paper will help researchers to systematically understand secondary battery technology and provide good guidance for future research on secondary batteries.![]()
The storage and utilization of energy is one of the important topics in the development of science and technology, especially regarding secondary batteries, which are efficient electrical-/chemical-energy-converting devices. This review systematically introduces the important research progress made in the context of secondary batteries, starting from their development and leading to the introduction of related basic theoretical knowledge. The current research on secondary batteries that are based on different systems and related key materials is discussed in detail, and includes lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, zinc-ion batteries, calcium-ion batteries, aluminum-ion batteries, fluorine-ion batteries, chloride-ion batteries, dual-ion batteries, lithium-sulfur (Se) batteries, sodium-sulfur (Se) batteries, potassium-sulfur (Se) batteries, polyvalent metal-sulfur-based batteries, lithium-oxygen batteries, sodium-oxygen batteries, potassium-oxygen batteries, aqueous metal-ion batteries, polyvalent metal-oxygen batteries, lithium-bromine (or lithium-iodine) batteries, photo-assisted batteries, flexible batteries, organic batteries, and metal-carbon dioxide batteries. Additionally, the common characterization techniques for electrode reaction processes in battery research are also introduced, including cryo-electron microscopy, transmission electron microscopy, synchrotron radiation, in situ spectroscopic techniques, and magnetic characterization. This paper will help researchers to systematically understand secondary battery technology and provide good guidance for future research on secondary batteries.
