Improving hole transfer of boron nitride quantum dots modified PDI for efficient photodegradation

Abstract

In recent years, organic photocatalyst under visible-light absorption has shown significant potential for solving environmental problems. However, it is still a great challenge for constructing a highly active organic photocatalyst due to the low separation efficiency of photogenerated carriers. Herein, an effective and robust photocatalyst perylene-3,4,9,10-tetracarboxylic diamide/boron nitride quantum dots (PDI/BNQDs), consisting of self-assemble PDI with π–π stacking structure and BNQDs, has been constructed and researched under visible light irradiation. The PDI/BNQDs composite gradually increases organic pollutant photodegradation with the loading amount of BNQDs. With 10 mL of BNQDs solution added (PDI/BNQDs-10), the organic pollutant photodegradation performance reaches a maximum, about 6.16 times higher with methylene blue and 1.68 times higher with ciprofloxacin than that of pure PDI supramolecular. The enhancement is attributed to improved separation of photogenerated carriers from self-assembled PDI by BNQDs due to their preeminent ability to extract holes. This work is significant for the supplement of PDI supramolecular composite materials. We believe that this photocatalytic design is capable of expanding organic semiconductors’ potential for their applications in photocatalysis.

Graphical abstract

Keywords

PDI / boron nitride / quantum dots / photocatalysis / hole transfer

Introduction

The interaction of high energy lasers with polymers can result in ablation of polymers at irradiated areas [1–11]. Laser ablation is a quick and efficient method to fabricate microstructures and devices on polymers because structures can be generated by a single laser pulse at a time scale of nanosecond or even shorter [1,3–5,10,11]. Ablated structures on polymers show many applications, such as superhydrophobic surfaces [6], multichip modules [7], distributed feedback lasers [4], inkjet printer nozzles [8], and diffractive optical elements [5].

Although laser ablation of polymers is extensively studied and shows many applications, studies on laser ablation of block copolymers (BCPs) are rare [9]. BCPs can form various microphase separated nanostructures [12]. The self-assembly of block copolymers is a promising platform for the fabrication of nanostructured materials and devices [13–20]. We previously reported that BCPs can be hierarchically structured by combining phase separation with laser interference ablation [10]. Shorter length scale structures of the hierarchical structures are phase separated nanostructures and longer length scale structures are interference patterns generated by laser ablation [10]. However, there is a lack of fundamental understanding of laser ablation of block copolymers. Understanding laser ablation of BCPs is helpful for the design of BCPs which can be effectively ablated and patterned. Additionally, lowering ablation thresholds of BCPs is important because low thresholds can increase the ablation rate and save energy. So, it is highly desirable to understand laser ablation of BCPs and decrease ablation thresholds of BCPs.

In this work, we studied the laser ablation of polystyrene-block-poly(4-vinyl pyridine) (PS-b-P4VP) with hydrogen-bonded azobenzene derivatives (AzoR). We found that the ablation threshold of BCP supramolecular assemblies PS-b-P4VP(AzoR) decreases as the concentration of AzoR increases. In PS-b-P4VP(AzoR) with different substituents (R= CN, H, and CH₃), ablation thresholds follow the trend: PS-b-P4VP(AzoCN)<PS-b-P4VP(AzoCH₃)<PS-b-P4VP(AzoH). We showed how chemical structures affect the laser ablation behavior of PS-b-P4VP(AzoR). According to these results, we can effectively fabricate tunable hierarchical structures on BCPs by laser ablation.

Experimental

Materials

The chemical structures of used materials are shown in Fig. 1. PS-b-P4VP (M_n = 330-b-125 kg·mol⁻¹ and PDI= 1.18) was purchased from Polymer Source. The azobenzene derivatives AzoCN and AzoCH₃ were synthesized according to our previous work [10,21]. AzoH was purchased from Aldrich.

Fig.1 Chemical structures of used materials. The azo compounds AzoR (R= CN, H, and CH3) are hydrogen bonded to P4VP blocks of PS-b-P4VP

Full size|PPT slide

Preparation of thin films

PS-b-P4VP and AzoR were dissolved in cyclopentane separately. Solutions of PS-b-P4VP(AzoR)_x were prepared by combining the above two solutions. Here, x denotes the molar ratio of AzoR versus repeat units of P4VP. The mixed solutions were stirred overnight and filtered through a 0.2 mm filter before use. Thin films of PS-b-P4VP(AzoR)_x were prepared by spin-coating. The films had a typical thickness of 200–230 nm. The spin-cast films were dried in an oven under vacuum at room temperature overnight. To induce phase separation, thin films were transferred to a glass container with saturated atmosphere of 1,4-dioxane. The container was completely closed and thin films were kept in the container for 2 days at room temperature.

Methods

Ultraviolet-visible (UV-vis) absorption spectra were measured on a Perkin-Elmer Lambda 900 UV-vis spectrometer. AFM images were obtained on a Dimension 3100 system using tapping mode. The optical setup for the three-beam interference was reported elsewhere [3,5,10,11]. In brief, a Q-switched Nd:YAG laser at 355 nm with laser pulse duration of 35 ns was used as the light source. The laser beam with pulse energy 1.18 mJ and a diameter of ~1.4 mm was split into three beams with equal intensity to overlap on the sample. The intersecting angle between the interference beams was 5.88°. Interference patterns were fabricated by single pulse irradiation. The intensity distribution of the interference pattern was calculated according to our previous work [3,5,11].

Results and discussion

Effects of the concentration of azobenzene derivatives on laser ablation

It is well known that small molecules with hydrogen bonding donors can be hydrogen-bonded to P4VP blocks of PS-b-P4VP [22–27]. Here, the phenolic group in AzoR is a hydrogen bonding donor (Fig. 1). AzoR can be hydrogen-bonded to P4VP [10,28,29]. The hydrogen bonding between AzoCN and P4VP is proved by infrared spectroscopy (Fig. S1, cf. Electronic Supplementary Material).

Figure 2 shows UV-vis absorption spectra of PS-b-P4VP(AzoCN)_x films with different concentrations of AzoCN. The band at 300–400 nm is the p-p* absorption band of azobenzene groups. The absorption coefficient (a) increases as the concentration of AzoCN increases.

Fig.2 UV-vis absorption spectra of thin films of PS-b-P4VP(AzoCN)x (x = 0.05, 0.1, 0.3, and 0.5)

Full size|PPT slide

PS-b-P4VP(AzoR)_x forms phase separated nanostructures (Fig. S2) [10]. The schematic model in Fig. 3(a) shows that PS forms the continuous phase and P4VP(AzoR)_x forms dispersed phases. Figure 3(c) shows the hexagonal interference pattern of three beams, which is calculated according to our previous work [3,5,11]. When PS-b-P4VP(AzoR)_x is exposed to interference beams, the polymers at bright interference fringes (high intensity areas) will be ablated. Hierarchical structures with both phase separated nanostructures and interference patterns can be obtained by laser interference ablation (Fig. 3(b)). We will show effects of the concentration of AzoCN on laser ablation.

Fig.3 Schematic models of PS-b-P4VP(AzoR)x (a) before and (b) after interference irradiation. After irradiation, periodic ablated areas (interference patterns) appear on PS-b-P4VP(AzoR)x. (c) Calculated intensity distribution (top) and profile (bottom) of three beam interference

Full size|PPT slide

Figure 4 shows atomic force microscope (AFM) images of PS-b-P4VP(AzoCN)_x (x = 0.05, 0.1, 0.3, and 0.5) after single pulse interference irradiation. All samples form hierarchical structures, which resemble the schematic model in Fig. 3(b). Shorter length scale structures of the hierarchical structures are phase separated nanostructures and longer length scale structures are interference patterns. AFM phase images (insets of Figs. 4(a–d)) clearly show the phase separation between PS and P4VP(AzoCN)_x. The average center-to-center distance (period) of nearby P4VP(AzoCN)_x phases increases form ~75 nm (x = 0.05) to ~105 nm (x = 0.5). The period of the interference patterns is ~2 µm. We compared the AFM profiles of PS-b-P4VP(AzoCN)_x with different x (Fig. 4(e)). PS-b-P4VP(AzoCN)_0.05 forms volcano-like structures, indicating its surface is swelled by laser beams. In the other samples, deep ablated holes are observed. PS-b-P4VP(AzoCN)_0.1 forms very sharp holes. PS-b-P4VP(AzoCN)_0.3 and PS-b-P4VP(AzoCN)_0.5 form deep and wide holes. The depth and diameter of the holes increases as the concentration of AzoCN increases (Fig. 4(f)).

Fig.4 AFM height images of PS-b-P4VP(AzoCN)x with different x after exposed to interference beams. (a) x = 0.05, (b) x = 0.1, (c) x = 0.3, and (d) x = 0.5. Insets are AFM phase images, which show that phase separated nanostructures in PS-b-P4VP(AzoCN)x; (e) profiles along the lines in (a)–(d); (f) depths and diameters of the holes generated by interference irradiation. Note: The diameters are measured at half depths of the holes

Full size|PPT slide

Effects of substituents of azobenzene derivatives on laser ablation

We also studied effects of substituents of azobenzene derivatives on laser interference ablation. The hydroxyl group on the para-position of azobenzene is an electron donor (D) [30]. The methyl group (CH₃) of AzoCH₃ is also an electron donor. The nitrile group (CN) of AzoCN is an electron acceptor (A). So, AzoH is a D-p molecule, AzoCH₃ is a D-p-D molecule, and AzoCN is a D-p-A molecule. These substituents affect the absorption of azo chromophores. Figure 5 shows UV-vis absorption spectra of AzoR in solutions and PS-b-P4VP(AzoR)_x films. The band at 300-400 nm is the characteristic absorption band of azobenzene groups. The bands of AzoCH₃ in solution and thin film slightly red-shift compared with those of AzoH. The bands of AzoCN obviously red-shift compared with those of AzoH. These results show that the D-p-D structure slightly affects the absorption of azo chromophores, and D-p-A structure strongly affects the absorption of azo chromophores.

Fig.5 UV-vis absorption spectra of (a) 10‒5 mol∙L‒1 AzoR in THF and (b) thin films of PS-b-P4VP(AzoR)0.5

Full size|PPT slide

Figure 6 shows AFM images of PS-b-P4VP(AzoH)_0.5 and PS-b-P4VP(AzoCH₃)_0.5 after interference irradiation. They form hierarchical structures with phase separated nanostructures and laser interference patterns. We compared the profiles of PS-b-P4VP(AzoR)_0.5 (Figs. 6(c) and 6(d)). PS-b-P4VP(AzoH)_0.5 forms sharp holes. The hole of PS-b-P4VP(AzoCH₃)_0.5 is slightly broader than that of PS-b-P4VP(AzoH)_0.5. The hole of PS-b-P4VP(AzoCN)_0.5 is much broader than that of PS-b-P4VP(AzoH)_0.5. These results indicate that the substituent of AzoR plays an important role on laser ablation.

The mechanism of laser ablation is as follows: When a target is irradiated by a high energy laser, the target absorbs light. Then, the target is heated or decomposed, and subsequent vaporization occurs [1–3,32]. PS-b-P4VP(AzoR)_x is different from normal targets because the light absorber AzoR is in P4VP phases but not homogenously dispersed in the matrix. When PS-b-P4VP(AzoR)_x is exposed to laser beams, AzoR is heated or decomposed. The heat diffuses to hydrogen bonded P4VP chains and nearby PS chains. The heated parts are ablated. P4VP(AzoR) phases are heating centers and the PS phase that does not absorb light obtains heat by thermal diffusion. Considering that the laser pulse duration is 35 ns and thermal diffusivity of PS is in the order of ~10⁻³ cm²∙s⁻¹ [33,34], the heated range of PS during an exposure time of a single pulse is several tens of nanometers near P4VP(AzoR) phases.

Fig.6 (a) AFM height images of PS-b-P4VP(AzoH)0.5 and (b) PS-b-P4VP(AzoCH3)0.5 after exposed to interference beams. Insets are AFM phase images of PS-b-P4VP(AzoR)0.5. The phase separated nanostructures are clearly visible in the AFM phase images; (c) profiles along the lines in (a), (b), and Fig. 4(d); (d) depths and diameters of the holes generated by interference irradiation. Note: the diameters are measured at half depths of the holes

Full size|PPT slide

The concentration of AzoCN affects the ablation process (Fig. 4). The reason is that AzoCN is the light absorber and the linear absorption coefficient of PS-b-P4VP(AzoCN)_x increases as x increases (Fig. 2 and Table 1). Ablation should be more efficient with more light absorbers. We calculated ablation thresholds of PS-b-P4VP(AzoCN)_x by AFM (Fig. S3). Ablation thresholds of PS-b-P4VP(AzoCN)_x decrease as x increases (Table 1). This result explains why different morphologies are generated on PS-b-P4VP(AzoCN)_x with different x (Fig. 4).

Tab.1 Linear absorption coefficients (a) at 355 nm and ablation thresholds of PS-b-P4VP(AzoR)x

Sample	a/104 cm−1	Threshold/(mJ∙cm−2)
PS-b-P4VP(AzoCN)0.05	0.57	\
PS-b-P4VP(AzoCN)0.3	3.61	81±10
PS-b-P4VP(AzoCN)0.5	5.35	47±10
PS-b-P4VP(AzoH)0.5	5.58	208±10
PS-b-P4VP(AzoCH3)0.5	5.75	165±10

Substituents of AzoR also affect the interference ablation (Fig. 6). As shown in Table 1, the linear absorption coefficients of PS-b-P4VP(AzoR)_0.5 (R= H, CN, and CH₃) are nearly the same, but their ablation thresholds are quite different. This result indicates that not only the linear absorption coefficient affects laser ablation. It is well known that azo dyes show nonlinear absorption, i.e., the absorption coefficient of an azo dye is strongly dependent on the laser intensity [30,35,36]. D-p-D and D-p-A molecules usually show better nonlinear absorption [30,35–38]. AzoCH₃ and AzoCN are D-p-D and D-p-A molecules, respectively, which can more efficiently absorb light of high energy lasers. So, different ablation thresholds of PS-b-P4VP(AzoR)_0.5 (R= H, CN, and CH₃) are due to different chemical structures of AzoR.

Conclusions

Both the concentration and the substituent of AzoR dominate the laser ablation of PS-b-P4VP(AzoR)_x. The ablation threshold decreases as the concentration of azobenzene derivatives increases. This result is because the linear absorption coefficient increases as the concentration of azobenzene derivatives increases. The samples with different substituents (PS-b-P4VP(AzoR)_0.5) have nearly the same linear absorption coefficient, but their ablation thresholds are quite different. Ablation thresholds follow the trend: PS-b-P4VP(AzoCN)_0.5<PS-b-P4VP(AzoCH₃)_0.5<PS-b-P4VP(AzoH)_0.5. This trend is due to the D-p-A and D-p-D structures of AzoCN and AzoCH₃, respectively. These results are helpful for the design of BCP systems with low ablation thresholds, which can be effectively structured at low laser intensities.

Tunable hierarchical structures can be fabricated by laser interference ablation of BCPs. Phase separated nanostructures are tunable by changing the composition of BCPs [10] or the concentration of azobenzene derivatives (insets of Fig. 4). Interferences patterns are tunable by changing interference conditions [10], concentration of azobenzene derivatives (Fig. 4), or substituents of azobenzene derivatives (Fig. 6). We observed that hierarchical structures on PS-b-P4VP(AzoR)_x show brilliant structural colors. The hierarchical structures show potential applications as photonic materials.

References

[1] Wang L, Zhang X, Yu X, Gao E, Shen Z, Zhang X, Ge S, Liu J, Gu Z J, Chen C. An all-organic semiconductor C₃N₄/PDINH heterostructure with advanced antibacterial photocatalytic therapy activity. Advanced Materials, 2019, 31(33): 190265

[2] Chen J, Li Y, Li J, Han J, Zhu G, Ren L. Crystal design of bismuth oxyiodide with highly exposed (110) facets on curved carbon nitride for the photocatalytic degradation of pollutants in wastewater. Frontiers of Chemical Science and Engineering, 2022, 16(7): 1125–1138

[3] Peng C, Jia Z, Zhong Y, Ao W, Chen D, Wang R, Ding H, Wu X, Wang J, Du G. Preparation of Bi_3.64Mo_0.36O_6.55 by reflux method and its application in photodegradation of organic pollution. Journal of Materials Science Materials in Electronics, 2021, 32(13): 17890–17900

[4] Zhong Y, He Z, Chen D, Hao D, Hao W. Enhancement of photocatalytic activity of Bi₂MoO₆ by fluorine substitution. Applied Surface Science, 2019, 467: 740–748

[5] Takeda H, Kamiyama H, Okamoto K, Irimajiri M, Mizutani T, Koike K, Sekine A, Ishitani O. Highly efficient and robust photocatalytic systems for CO₂ reduction consisting of a Cu(I) photosensitizer and Mn(I) catalysts. Journal of the American Chemical Society, 2018, 140(49): 17241–17254

[6] Miao H, Yang J, Wei Y, Li W, Zhu Y. Visible-light photocatalysis of PDI nanowires enhanced by plasmonic effect of the gold nanoparticles. Applied Catalysis B: Environmental, 2018, 239: 61–67

[7] Hu D, Fu J, Chen S, Li J, Yang Q, Gao J, Tang H, Kan Z, Duan T, Lu S, Sun K, Xiao Z. Block copolymers as efficients cathode interlayer materials for organic solar cells. Frontiers of Chemical Science and Engineering, 2021, 15(3): 571–578

[8] Fang X, Shang Q, Wang Y, Jiao L, Yao T, Li Y, Zhang Q, Luo Y, Jiang H L. Single Pt atoms confined into a metal-organic framework for efficient photocatalysis. Advanced Materials, 2018, 30(7): 1705112

[9] Wang G, He C T, Huang R, Mao J, Wang D, Li Y. Photoinduction of Cu single atoms decorated on UiO-66-NH₂ for enhanced photocatalytic reduction of CO₂ to liquid fuels. Journal of the American Chemical Society, 2020, 142(45): 19339–19345

[10] Zhao Y, Liu H, Wu C, Zhang Z, Pan Q, Hu F, Wang R, Li P, Huang X, Li Z. Fully sp²-carbon conjugated two-dimensional covalent organic frameworks as artificial photosystem I with unprecedented efficiency. Angewandte Chemie International Edition, 2019, 58(16): 5376–5381

[11] Wang S, Li D, Sun C, Yang S, Guan Y, He H. Synthesis and characterization of g-C₃N₄/Ag₃VO₄ composites with significantly enhanced visible-light photocatalytic activity for triphenylmethane dye degradation. Applied Catalysis B: Environmental, 2014, 144: 885–892

[12] Liao G, Gong Y, Zhang L, Gao H, Yang G J, Fang B. Semiconductor polymeric graphitic carbon nitride photocatalysts: the “holy grail” for the photocatalytic hydrogen evolution reaction under visible light. Energy & Environmental Science, 2019, 12(7): 2080–2147

[13] Li X B, Liu J Y, Huang J T, He C Z, Feng Z J, Chen Z, Wan L F, Deng F. All organic S-scheme heterojunction PDI-Ala/S-C₃N₄ photocatalyst with enhanced photocatalytic performance. Acta Physico Chimica Sinica, 2021, 37(6): 2010030

[14] Yang J, Miao H, Jing J, Zhu Y, Choi W. Photocatalytic activity enhancement of PDI supermolecular via π–π action and energy level adjusting with graphene quantum dots. Applied Catalysis B: Environmental, 2021, 281: 119547

[15] Fateeva A, Chater P A, Ireland C P, Tahir A A, Khimyak Y Z, Wiper P V, Darwent J R, Rosseinsky M J. A water-stable porphyrin-based metal–organic framework active for visible-light photocatalysis. Angewandte Chemie International Edition, 2021, 51(30): 7440–7444

[16] Rafiq M, Chen Z, Tang H, Hu Z, Zhang X, Xing Y, Li Y, Huang F. Water-alcohol-soluble hyperbranched polyelectrolytes and their application in polymer solar cells and photocatalysis. ACS Applied Polymer Materials, 2020, 2(1): 12–18

[17] Zhang Z, Zhu Y, Chen X, Zhang H, Wang J. A full-spectrum metal-free porphyrin supramolecular photocatalyst for dual functions of highly efficient hydrogen and oxygen evolution. Advanced Materials, 2019, 31(7): 1806626

[18] Weingarten A S, Kazantsev R V, Palmer L C, McClendon M, Koltonow A R, Samuel A P S, Kiebala D J, Wasielewski M R, Stupp S I. Self-assembling hydrogel scaffolds for photocatalytic hydrogen production. Nature Chemistry, 2014, 6(11): 964–970

[19] Chen P, Blaney L, Cagnetta G, Huang J, Wang B, Wang Y, Deng S, Yu G. Degradation of ofloxacin by perylene diimide supramolecular nanofiber sunlight-driven photocatalysis. Environmental Science & Technology, 2019, 53(3): 1564–1575

[20] Gao Q, Xu J, Wang Z, Zhu Y. Enhanced visible photocatalytic oxidation activity of perylene diimide/g-C₃N₄ n–n heterojunction via π–π interaction and interfacial charge separation. Applied Catalysis B: Environmental, 2020, 271: 118933

[21] Cheng W, Chen H, Ji C, Yang R, Yin M. A perylenediimide-based nanocarrier monitors curcumin release with an “off–on” fluorescence switch. Polymer Chemistry, 2019, 10(20): 2551–2558

[22] Zhang Z, Zhang L, Zhou L, Lei Y, Zhang Y, Huang C. Redox signaling and unfolded protein response coordinate cell fate decisions under ER stress. Redox Biology, 2019, 25: 101047

[23] Jung T H, Yoo B, Wang L, Dodabalapur A, Jones B A, Facchetti A, Wasielewski M R, Marks T J. Nanoscale n-channel and ambipolar organic field-effect transistors. Applied Physics Letters, 2006, 88(18): 183102

[24] Cheng H, Huai J, Gao L, Li Z. Novel self-assembled phosphonic acids monolayers applied in N-channel perylene diimide (PDI) organic field effect transistors. Applied Surface Science, 2016, 378: 545–551

[25] Macedo A G, Christopholi L P, Gavim A E X, de Deus J F, Teridi M A M, Yusoff A B, da Silva W J. Perylene derivatives for solar cells and energy harvesting: a review of materials, challenges and advances. Journal of Materials Science Materials in Electronics, 2019, 30(17): 15803–15824

[26] Dayneko S V, Cieplechowicz E, Bhojgude S S, Van Humbeck J F, Pahlevani M, Welch G C. Improved performance of solution processed OLEDs using N-annulated perylene diimide emitters with bulky side-chains. Materials Advances, 2021, 2(3): 933–936

[27] Ma L, Qin D, Liu Y, Zhan X. n-Type organic light-emitting transistors with high mobility and improved air stability. Journal of Materials Chemistry C, 2018, 6(3): 535–540

[28] Yang J, Liu C, Cai C, Hu X, Huang Z, Duan X, Meng X, Yuan Z, Tan L, Chen Y. High-performance perovskite solar cells with excellent humidity and thermo-stability via fluorinated perylene diimide. Advanced Energy Materials, 2019, 9(18): 1900198

[29] Kim Y O, Moon B J, Lee A, Kim J I, Lee S K, Lee Y S, Bae S, Hong B H, Jung Y C. A multifunctional tyrosine-immobilized PAH molecule as a universal cathode interlayer enables high-efficiency inverted polymer solar cells. Advanced Optical Materials, 2021, 9(21): 2101006

[30] Wang W, Li X, Deng F, Liu J, Gao X, Huang J, Xu J, Feng Z, Chen Z, Han L. Novel organic/inorganic PDI-urea/BiOBr S-scheme heterojunction for improved photocatalytic antibiotic degradation and H₂O₂ production. Chinese Chemical Letters, 2022, 33(12): 5200–5207

[31] Li X, Kang B, Dong F, Deng F, Han L, Gao X, Xu J, Hou X, Feng Z, Chen Z, Liu L, Huang J. BiOBr with oxygen vacancies capture 0D black phosphorus quantum dots for high efficient photocatalytic ofloxacin degradation. Applied Surface Science, 2022, 539: 153422

[32] Wei W, Wei Z, Liu D, Zhu Y. Enhanced visible-light photocatalysis via back-electron transfer from palladium quantum dots to perylene diimide. Applied Catalysis B: Environmental, 2018, 230: 49–57

[33] Han R, Liu F, Wang X, Huang M, Li W, Yamauchi Y, Sun X, Huang Z. Functionalised hexagonal boron nitride for energy conversion and storage. Journal of Materials Chemistry A, 2020, 8(29): 14384–14399

[34] Li H, Tay R Y, Tsang S H, Zhen X, Teo E H T. Controllable synthesis of highly luminescent boron nitride quantum dots. Small, 2015, 11(48): 6491–6499

[35] Yang Y, Zhang C, Huang D, Zeng G, Huang J, Lai C, Zhou C, Wang W, Guo H, Xue W, Deng R, Cheng M, Xiong W. Boron nitride quantum dots decorated ultrathin porous g-C₃N₄: intensified exciton dissociation and charge transfer for promoting visible-light-driven molecular oxygen activation. Applied Catalysis B: Environmental, 2019, 245: 87–99

[36] Guo Y, Nie Y, Liang Z, Peilin W, Ma Q. Ag₃PO₄ NP@MoS₂ nanosheet enhanced F, S-doped BN quantum dot electrochemiluminescence biosensor for K-ras tumor gene detection. Talanta, 2021, 228: 122221

[37] Huo B, Liu B, Chen T, Cui L, Xu G, Liu M, Liu J. One-step synthesis of fluorescent boron nitride quantum dots via a hydrothermal strategy using melamine as nitrogen source for the detection of ferric ions. Langmuir, 2017, 33(40): 10673–10678

[38] Wei Z, Liu M, Zhang Z, Yao W, Tan H, Zhu Y. Efficient visible-light-driven selective oxygen reduction to hydrogen peroxide by oxygen-enriched graphitic carbon nitride polymers. Energy & Environmental Science, 2018, 11(9): 2581–2589

[39] Li C, Che H, Liu C, Che G, Charpentier P A, Xu W, Wang X, Liu L. Facile fabrication of g-C₃N₄ QDs/BiVO₄ Z-scheme heterojunctiontowards enhancing photodegradation activity under visible light. Journal of the Taiwan Institute of Chemical Engineers, 2019, 95: 669–681

[40] Cassabois G, Valvin P, Gil B. Hexagonal boron nitride is an indirect bandgap semiconductor. Nature Photonics, 2016, 10(4): 262–266

[41] Ding Y, He P, Li S, Chang B, Zhang S, Wang Z, Chen J, Yu J, Wu S, Zeng H, Tao L. Efficient full-color boron nitride quantum dots for thermostable flexible displays. ACS Nano, 2021, 15(9): 14610–14617

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was partly supported by the National Natural Science Foundation of China (Grant No. 21978276), and the Fundamental Research Funds for the Central Universities (Grant Nos. 2652019157, 2652019158, and 2652019159).

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-023-2319-7 and is accessible for authorized users.

RIGHTS & PERMISSIONS

2023 Higher Education Press