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Small Carbon Quantum Dots, Large Photosynthesis Enhancement
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Yan Gong*,† and Jie Zhao† School of Life Sciences, Shanxi Normal University, Linfen 041004, P. R. China scintillation phenomenon (Unable to achieve single molecule luminescence applications) and cytotoxicity of semiconductor QDs, they cannot be widely applied in the field of botany.11 Carbon nanomaterials are the carbon materials with dispersed phase scales that have at least one dimensionality less than 100 nm, and can adequately overcome the abovedescribed disadvantages of traditional organic dyes and semiconductor QDs. Iverson et al.12 found that single-walled carbon nanotubes could enter into isolated chloroplasts through passive transport, were irreversibly concentrated on the lipid membrane, and could enhance the photosynthetic activity more than three times and increase the threshold of electron transfer. Studies conducted by Goswami et al. found that the aminated carbon nanometer materials had a stronger affinity with the chloroplast, which could efficiently transfer electrons from PS I to PS II and increase the conversion ability among light energy, electric energy, and chemical energy. During this process, the oxygen decomposition capacity, hotosynthesis maintains the carbon and oxygen cycle on noncyclic photosynthetic phosphorylation, and ATP synthase Earth, which is the foundation for organisms to exist. activity in the isolated chloroplast all increased. Artificially simulated photosynthesis can convert solar energy As a new type of fluorescent carbon nanomaterial, the into electrochemical energy, thus efficiently utilizing solar average particle size of carbon quantum dots (CQDs) is less energy, and this has been the focus of chemistry, material than 10 nm. Due to the characteristics of high chemical science, and energy science research.1 Research has indicated stability, tolerance to photobleaching, facilitating functionalizathat the combination of biomaterials and semiconductor tion, and low biological toxicity, they are frequently used as nanometer materials could improve the photoelectric confluorescent tags for biological and chemical analysis as well as version efficiency of the latter.2 However, fewer studies have fluorescence imaging.13 The doping modification of CQDs can been conducted revealing whether the photoelectric conincrease the amount of transferred charges at the interface, and version capability of nanometer materials could promote electronic holes can be generated under light irradiation which photosynthetic efficiency in plants through combining increases the photoelectricity conversion efficiency.14 At 3 present, the doping of CQDs mainly uses heteroatoms (N, biosciences. P, S, Cl, and B),15 and there are few reports on rare-earth The light-harvesting complexes (LHC) of the photosystems chelate doped CQDs. Recently, Ren et al.16 adjusted the are the most important membrane proteins in the photosystem 4 carbonized degree of precursor gadopentetate monomegluof higher plants. The light absorption of LHC is concentrated mine through regulating the pyrolysis temperature and heat on the visible wavelengths between 400 and 700 nm, and little preservation time, and gadolinium chelate doped fluorescent is absorbed in green light and ultraviolet wavelengths.5 Wildcarbon quantum dots (Gd(III)-CQDs) containing a magnetic type LHC can be constructed in vitro, dock with organic or resonance response were obtained, which could be used as inorganic molecules,6 and also be used to construct hybrid probes for bimodal molecular imaging. It has been speculated complexes with improved or novel functions.7 that applying different rare-earth elements, chelating agents, or Quantum dots (QDs) from semiconductor materials are an appropriate ligands for precursor preparation and utilizing important representative of nanometer materials, and are different pyrolysis temperatures for each group of small wildly applied in the fields of analytical chemistry and 8 molecule rare-earth chelates could allow the production of bioimaging. QDs are excellent energy donors in the different rare-earth chelate doped CQDs through controlling fluorescence resonance energy transfer (FRET) system. reaction conditions. Erker9 and Yang10 connected QDs to the LHC II, respectively. Rare-earth elements (RE) have particular optical properties It was found that QDs could transmit partial excitation energy (including stronger light emission, long life, and high quantum to LHC II through resonance energy transfer, promote the efficiency). Numerous experiments have shown that at a efficiency of light energy utilization of LHC II, and improved certain concentration, RE significantly facilitate photosynthesis. the capacity for energy transfer with the increased molar ratio of hybrid complex QDs to LHC II, but the mechanism and influence on energy transfer between semiconductor QDs and Received: April 10, 2018 LHC were still undefined. In addition, due to the light
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© XXXX American Chemical Society
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DOI: 10.1021/acs.jafc.8b01788 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Journal of Agricultural and Food Chemistry
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ACKNOWLEDGMENTS This work was supported by National Natural Science Foundation of China (31700876, 31700862), Natural Science Foundation of Shanxi Province (201601D021106), and Basic Research Program of Shanxi Normal University (ZR1602).
Rare-earth elements could improve the Hill reaction rate, stimulate the photosynthetic phosphorylation rate of chloroplasts, and accelerate the photoreaction rate in photosynthesis. They could also promote the synthesis of chlorophyll and offset the Mg2+ function of chlorophyll. The influence of REs on photosynthesis has had no unanimous conclusions until now.17 Utilizing rare-earth elements for doping modification on CQDs also can improve the stability and optical properties of CQDs, and unique optical and magnetic characteristics are generated. Recently, Song et al.18 prepared dual-light-emission CQDs doped with europium (Eu) chelate through pyrolysis. The Eu-doped CQDs had size-dependent optoelectronic properties, high fluorescence quantum efficiency, good optical and chemical stabilities. The fluorescent properties of Eudoped CQDs could be changed through adjusting and controlling its size, structure, morphology, and doping. Considering that the two emission peaks of Eu-doped CQDs were located at approximately 360−550 nm and 550−750 nm, which is a large overlap with wavelengths available to chloroplasts, it has been speculated that, under a short distance, the Eu-doped CQDs could have a resonance energy transfer with chloroplasts as energy donors, improving the light energy utilization efficiency of the latter. Under appropriate conditions, both the rare-earth elements19 and carbon nanomaterials12 can improve the efficiency of photoelectric transfer within a plant and increase the efficiency of light energy utilization, respectively. By utilizing the different pyrolysis temperatures of each group in small molecule rare-earth chelates through controlling the reaction conditions, the preparation of rare-earth chelate doped fluorescent CQDs (RE-CQDs) could be realized. In addition, the effects of RE-CQDs on plant photosynthetic physiology and biochemistry deserve systematic study. This could provide evidence for the selection of plant nanobionic engineering materials and lay the foundation for the evaluation of the potential effects of rare-earth element doped carbon nanomaterials on the environment, further providing a technical reference for the application of nanometer materials in actual production and life. Meanwhile, future studies will explore the effect of RE-CQDs assemblies on the carbon reactions of photosynthesis and chloroplast sugar export. Nanomaterial enhancement of isolated chloroplast stability to free radicals and higher photosynthetic effciencies opens the possibility of creating hyperstable synthetic materials that grow and repair themselves using sunlight, water, and carbon dioxide.12 Based on an in-depth understanding of the mechanism of absorption transport and distribution of RE-CQDs, we can develop nanofertilizers suitable for agricultural production.
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REFERENCES
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Yan Gong: 0000-0003-0959-0572 Author Contributions †
Y.G. and J.Z. contributed equally to this work.
Notes
The authors declare no competing financial interest. B
DOI: 10.1021/acs.jafc.8b01788 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
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Journal of Agricultural and Food Chemistry (19) Ř ezanka, T.; Kaineder, K.; Mezricky, D.; Ř ezanka, M.; Bišová, K.; Zachleder, V.; Vítová, M. The effect of lanthanides on photosynthesis, growth, and chlorophyll profile of the green alga Desmodesmus quadricauda. Photosynth. Res. 2016, 130, 335.
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DOI: 10.1021/acs.jafc.8b01788 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
