English

• Gold nanoclusters (AuNCs), as a novel class of nanomaterials, have drawn widespread attentions recently [1-6]. Due to their ultra-small size, tunable fluorescence properties and good biocompatibility, AuNCs have shown great application prospects in sensing [7], imaging [8], disease diagnosis and treatment [9]. AuNCs possess a unique core–shell structure comprising of the Au(0) core and the Au(Ⅰ)–ligand shell [10]. Particularly, the surface ligands pose a crucial impact on the synthesis, property and application of AuNCs. On the one hand, ligands can control cluster growth and stabilize the cluster structure through strong interactions with core atoms [11]. On the other hand, the surface ligands of AuNCs can alter their geometry and electronic structure through electronic interactions with gold atoms, thereby affecting their stability, optical and other properties [12-14]. Moreover, the ligands situated in the outermost layer can interact with the external environment (e.g., ions, biomolecules, and cells) and directly determine the performance of AuNCs, such as the targeting property and biological stability [15-17]. Consequently, designing and regulating the surface ligands to synthesize new types of fluorescent AuNCs with unique properties has become an effective strategy currently.

  Au atoms can be bonded with various organic ligands via versatile bonding modes. Up to date, a range of organic ligands including phosphine, thiolate, halogen, alkynyl, N-heterocyclic carbenes (NHCs), and nitrogenous ligands (e.g., pyridyl and amidinate) have been utilized to stabilize AuNCs [18]. Among these ligands, most previous studies have predominantly concentrated on thiolate-modified AuNCs, largely due to their reasonable stability. Recently, it has been reported that enhanced stability in AuNCs can be achieved by substituting thiolate with selenolate [19]. Sulfur (S) and selenium (Se) belong to the same group of the periodic table. In comparison with S, the electronegativity and atomic radius of Se are closer to those of gold. As a result, the Au–Se bond is more covalent and possesses a higher bond energy than Au–S [20-22]. It is expected that selenolate-capped AuNCs will be more stable than thiolate-modified AuNCs. In an early study, Negishi et al. have succeeded in directly synthesizing [Au₂₅(SeC₈H₁₇)₁₈] for the first time, and compared the stability of Au₂₅(SC₈H₁₇)₁₈ and Au₂₅(SeC₈H₁₇)₁₈ [23,24]. They found that selenolate-protected AuNCs have higher thermal and chemical stabilities. Moreover, Tang et al. reported that the nanoplatform based on the Au‒Se bond exhibited excellent resistance to biothiol interference compared with the Au-S nanoplatform [25,26], which is of great significance for the biological application. Furthermore, selenium, as an essential trace element for the human body, has many biological functions. For instance, a large quantity of studies have shown that selenium can reduce the occurrence of cancer, and exogenous supplementation of selenium can prevent and inhibit various tumors induced by carcinogens [27,28]. However, there are few studies on the synthesis and property research of water-soluble selenolate-protected AuNCs at present. Therefore, synthesizing water-soluble luminescent AuNCs and investigating the influence of selenolate ligands on their optical properties is of great importance for further advancing their biological applications (e.g., cell imaging).

  Herein, we employed commercially available benzeneselenol (PhSeH) as a model selenolate ligand and glutathione (GSH) as co-ligands to synthesize selenolate-costabilized water-soluble, near-infrared (NIR) fluorescent AuNCs. In particular, the role of PhSeH on the optical property of AuNCs was systematically investigated, which revealed that the PhSeH content can significantly regulate the optical properties of AuNCs. The fluorescence quantum yield reaches the maximum value when PhSeH content is 5%, and the fluorescence stability of AuNCs increases as the PhSeH content increases. Moreover, the effect of PhSeH content also affected the cell imaging performance of AuNCs, such as the cellular uptake rate and imaging property. These results provide important knowledges for further development of new, robust selenolate-stabilized metal NCs for biological application.

  AuNCs were first synthesized via a one-step reduction method in the presence of both GSH and PhSeH via a modified strategy [29]. In order to obtain superior fluorescent AuNCs, the reaction conditions have been optimized. Firstly, we optimized the molar ratio of total ligand to Au³⁺, with the maximum fluorescence intensity observed at a molar ratio of 1.3:1. As shown in Fig. S1 (Supporting information), when the molar ratio is either lower or higher, the fluorescence of product will become weaker (Fig. S1A). Alkalinity of the reaction solution is also a vital factor, and the optimal amount of added NaOH was found to be 20 mmol/L (Fig. S1B). Moreover, adding NaOH before HAuCl₄ can enhance the fluorescence intensity of obtained AuNCs, since NaOH can increase the solubility of PhSeH in aqueous solution (Fig. S1C). Meanwhile, the fluorescence of obtained AuNCs was the strongest after reacting for 18 h (Fig. S1D). The effect of additional reducing agents, such as ascorbic acid (Fig. S1E), tetrakis(hydroxymethyl)phosphonium chloride (Fig. S1F) on the optical property of AuNCs was also investigated. The results suggested that the emission peak of AuNCs obtained in the existence of both reducing agents did not shift, while fluorescence intensity decreased compared to those AuNCs obtained without reducing agents.

  In order to investigate the effect of PhSeH on the properties of AuNCs, we synthesized four types of AuNCs with different amounts of PhSeH while keeping the total amount of surface ligands unchanged: AuNCs-0, AuNCs-1, AuNCs-2, AuNCs-3, which contains 0%, 3%, 5%, 10% of PhSeH, respectively (Scheme 1). Transmission electron microscopy (TEM) images showed that the prepared AuNCs all exhibit good mono-dispersity, and the core size of AuNCs was measured to be 1.43 ± 0.02, 1.59 ± 0.04, 1.61 ± 0.02 and 1.59 ± 0.05 nm for AuNCs-0, AuNCs-1, AuNCs-2 and AuNCs-3, respectively (Fig. 1). This result indicates that the size of AuNCs slightly increased after the addition of PhSeH, which is likely due to the hydrophobicity feature of PhSeH that affects the core growth in aqueous medium during the synthesis. Moreover, all four types of AuNCs have similar hydrodynamic size. However, zeta potential measurements suggested that concomitant with the PhSeH content increase, the surface of AuNCs have more negative charges (Table 1), supporting the successful introduction of selenolate ligands. Furthermore, the Se content of AuNCs-1, AuNCs-2 and AuNCs-3 was quantitatively measured by inductively coupled plasma optical emission spectroscopy (ICP-OES). As shown in Table 1, the Se content in three AuNCs adheres to the expected order: AuNCs-1 < AuNCs-2 < AuNCs-3, which is also in good accordance with the relative amounts of PhSeH ligands in the synthesis process.

  Scheme1

  

  Scheme1.  Schematic illustration of the synthesis of AuNCs with different PhSeH contents.

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  Figure 1

  

  Figure 1.  TEM images of AuNCs-0 (A), AuNCs-1 (B), AuNCs-2 (C) and AuNCs-3 (D). Insets are the size histograms of AuNCs based on TEM images.

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  Table 1

  

  Table 1.  Summary of the characterization results of the physicochemical properties of different AuNCs.

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  Property	AuNCs-0	AuNCs-1	AuNCs-2	AuNCs-3
  Core size (nm)	1.43 ± 0.02	1.58 ± 0.03	1.60 ± 0.02	1.59 ± 0.05
  Hydrodynamic size (nm)	2.9 ± 0.2	3.0 ± 0.3	3.7 ± 0.4	3.8 ± 0.4
  Zeta potential (mV)	−33.1 ± 0.2	−33.0 ± 1.7	−35.3 ± 0.4	−36.4 ± 0.3
  Se content (µg/mL)	0	7.96	10.34	15.50
  Emission maximum (nm)	816	816	818	820
  Quantum yield (%)	0.8	2.2	3.1	2.5
  Fluorescence lifetime (µs)	2.20 ± 0.06	3.56 ± 0.12	3.95 ± 0.06	3.62 ± 0.08

  We next investigated the effect of PhSeH on the optical properties of these AuNCs. The absorption spectra of AuNCs does not exhibit plasmon absorption peak at 520 nm, which confirms the formation of small sized AuNCs (Fig. 2A). The fluorescence properties of these AuNCs are significantly different, although they all display an obvious emission band in the NIR range, with the emission peak at around 820 nm. Notably, the peak intensity follows the order: AuNCs-2 > AuNCs-3 > AuNCs-1 > AuNCs-0. All three AuNCs with co-stabilized PhSeH on the surfaces exhibited stronger intensity than AuNCs-0, with AuNCs-2 containing 5% of PhSeH showing the maximum emission intensity. This observation was further confirmed from three-dimensional (3D) fluorescence spectroscopy, as shown in Figs. 2B–E. The 3D spectra also showed that the emission of these AuNCs was excitation-independent, which is similar as reported AuNCs. Particularly, Jin et al. disclosed that the energy of luminescence is primarily influenced by the kernel structure of AuNCs, whereas the QY of AuNCs is significantly affected by the interactions between the gold atoms and surface ligands [30]. Indeed, absolute quantum yield (QY) measurement showed that AuNCs-0, AuNCs-1, AuNCs-2 and AuNCs-3 possess a QY of 0.8%, 2.2%, 3.1% and 2.5%, respectively (Table 1), which also agree with the spectral results. Despite lower than the QY of semiconductor quantum dots and some NIR dyes, we note that this QY (2%–3%) in the NIR region is sufficient for further bio-imaging applications.

  Figure 2

  

  Figure 2.  (A) Ultraviolet-visible absorption and fluorescence emission spectra of different AuNCs in aqueous solution. Excitation wavelength: 400 nm. 3D fluorescence spectra of AuNCs-0 (B), AuNCs-1 (C), AuNCs-2 (D) and AuNCs-3 (E). (F) Photoluminescence decay profiles of different AuNCs in aqueous solution and the fitting results. Excitation wavelength: 405 nm.

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  Fluorescence lifetime, as one of the key parameters of optical properties of AuNCs, was further measured to elucidate the underlying reason for their different fluorescence intensity. The fluorescence lifetime of these AuNCs was calculated by fitting the decay curve with tri-exponential decay components. As seen in Fig. 2F, along with the intensity increase, the fluorescence decay of AuNCs co-stabilized by selenolate ligands (AuNCs-1, AuNCs-2 and AuNCs-3) was longer than that stabilized solely by thiolates (AuNCs-0). The microsecond radiative lifetimes of these AuNCs demonstrated that their emission could be mainly ascribed to the ligand to metal charge transfer (LMCT) effect [31-33]. Meanwhile, further analysis revealed that the fraction of the long lifetime component increased together with a decrease in the short lifetime component. As summarized in Table S1 (Supporting information), the component with the longest lifetime (τ₃) played a crucial role in increasing lifetime compared to the other two components. The long lifetime component is generally associated with the Au(Ⅰ)-ligand motifs on the surface of AuNCs [34-36], suggesting that the surface ligands of AuNCs have experienced significant changes due to the presence of PhSeH.

  In order to evaluate the possible effect of PhSeH on the chemical structure of AuNCs, X-ray photoelectron spectroscopy (XPS) of four AuNCs was measured. As shown in Figs. 3A, the characteristic peaks at around 84.0 eV can be attributed to Au 4f_7/2 for these AuNCs, indicating the presence of both Au(0) and Au(Ⅰ) components in the clusters [37]. Further quantitative analysis based on XPS showed that the fraction of Au(Ⅰ) in these four AuNCs also followed the order: AuNCs-2 > AuNCs-3 > AuNCs-1 > AuNCs-0 (Fig. 3B), in accordance with their QY trend. Due to the charge transfer from the ligand to the gold core, the Au(Ⅰ) complexes contribute to the luminescence of AuNCs, which can account for the change of fluorescence intensity of these four AuNCs [38]. Meanwhile, it is noteworthy that hydrophobic PhSeH can prevent water molecules from approaching AuNCs, further resist fluorescence quenching. As shown in Fig. 3C, the binding energy of S 2p peak located at 162.7, 162.4, 162.4, 162.1 eV for AuNCs-0, AuNCs-1, AuNCs-2 and AuNCs-3, respectively, suggesting the binding of S from GSH to Au. Apparently, the slightly decreased binding energy of S in the latter three AuNCs is caused by the co-stabilized selenolate ligands, which affects the electronic state of S in AuNCs. Moreover, we note that the oxidized sulfur peak (167.4 eV) appeared in AuNCs-1, AuNCs-2 and AuNCs-3, and the percentage of oxidized sulfur increased with raising the PhSeH content. Herein, the presence of oxidized sulfur may also play a role in promoting the fluorescence generation of AuNCs, which has been reported for other AuNCs in previous studies [39]. The XPS peak of Se 3d was also observed from AuNCs-1, AuNCs-2 and AuNCs-3 (Fig. 3D), which further confirmed the presence of PhSeH on their surfaces. The binding energy accords with reported values for Se bonding to Au [20].

  Figure 3

  

  Figure 3.  (A) XPS spectra of Au 4f in different AuNCs, and (B) the fraction of Au(Ⅰ) based on XPS data fitting. XPS spectra of S 2p (C) and Se 3d (D) in different AuNCs and the fitting results. All data are presented as mean ± standard deviation (SD) (n = 3).

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  The photostability of these AuNCs was then investigated upon continuous UV irradiation at 400 nm. As shown in Fig. 4A, the fluorescence intensity of AuNCs-0 decreased by ca. 32% after 5 min. In contrast, AuNCs-1, AuNCs-2 and AuNCs-3 showed much better photostability, as reflected by less than 20% of intensity loss in the same time range. We also investigated the long-term stability of these AuNCs by monitoring their fluorescence property in aqueous medium (Fig. 4B). Similarly, AuNCs-1, AuNCs-2 and AuNCs-3 showed negligible change of fluorescence property after storage for 1 week, while the fluorescence property of AuNCs-0 decreased by ca. 25%. These results all demonstrate that the stability of GSH-stabilized AuNCs was enhanced upon co-stabilized by selenolate ligands, owing to the introduction of stronger Au-Se bond than Au-S bond. Moreover, the fluorescence property of these AuNCs showed a good stability in a wide pH range from 4.0 to 10.0 (Fig. 4C). These distinct features make selenolate-stabilized AuNCs promising as optical probes for biological applications.

  Figure 4

  

  Figure 4.  (A) Time-dependent fluorescence intensity change of different AuNCs at 820 nm under UV irradiation. (B) Fluorescence stability of different AuNCs after storage in aqueous solution for different days. (C) Fluorescence stability of different AuNCs in the solution with different pH. The cell viability of (D) L929 cells and (E) B16F10 cells upon being incubated with four types of AuNCs at different concentrations. (F) Uptake efficiency of different AuNCs by L929 and B16F10 cells based on ICP-OES measurements. All data are presented as mean ± SD (n = 3). *P < 0.05, **P < 0.01.

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  AuNCs have shown great promise as novel nanoprobes in the field of bioimaging, where good biocompatibility is an essential requirement. Moreover, it is important to understand how the content of PhSeH affects the biocompatibility of these AuNCs. Thus, the cytotoxicity of these AuNCs stabilized with different PhSeH contents was first investigated, and two cell lines (L929 and B16F10 cells) were chosen in the study. As shown in Figs. 4D and E, the cell counting kit-8 (CCK-8) assays showed cell viability remains almost unchanged upon incubating with all four AuNCs at a concentration up to 100 µg/mL for both L929 cells and B16F10 cells. However, when increasing the concentration up to 200 µg/mL, the cell viability of B16F10 cells was lower than 60% upon incubating with AuNCs-2 and AuNCs-3. The observed cytotoxicity of AuNCs with higher PhSeH content was not surprising, considering exogenous supplementation of selenium could prevent and inhibit various tumors induced by carcinogens according to previous reports. For example, Bielawski et al. reported that Se nanoparticles exhibited anti-cancer effects on human melanoma and glioblastoma cells [40]. It is difficult to directly compare their uptake efficiency through fluorescence imaging due to distinct intrinsic fluorescence QY of these AuNCs. Therefore, ICP-OES was utilized to quantitatively compare their cellular uptake efficiency, and the amount of Au internalized into L929 or B16F10 cells after 2 h incubation was measured. As shown in Fig. 4F, for both cell lines, cellular uptake efficiency was higher for AuNCs with more PhSeH content, following the order: AuNCs-3 > AuNCs-2 > AuNCs-1 > AuNCs-0. Up to now, numerous studies on the cellular uptake mechanism of AuNCs indicated the importance of their sizes and surface properties. As shown in Table 1, all four types of AuNCs have similar hydrodynamic size, indicating that the size does not have a major impact on their uptake efficiency. However, zeta potential measurement showed that concomitant with the PhSeH content increase, AuNCs possess more negative charges on the surfaces. AuNCs with more negative charges will have a higher cellular uptake level as they will interact strongly with the positively charged sites of the cell membrane [41]. Thus, the observed favorable uptake of AuNCs with more selenolate ligands is more likely due to their abundant surface charges. Moreover, the higher content of PhSeH on the surface of AuNCs increases their lipophilicity, enabling stronger interactions with the phospholipids in the cell membrane, which may also facilitate the cellular uptake.

  The potential use of these biocompatible, NIR fluorescent AuNCs for live cell imaging was finally investigated by virtue of their intrinsic fluorescence features. As evident from Fig. 5A, upon treatment of L929 cells with 100 µg/mL of AuNCs-0 for 2 h, no significant luminescence was observed upon excitation at 405 nm. In contrast, upon treatment with AuNCs-1, AuNCs-2 or AuNCs-3, bright red luminescence could be observed in L929 cells, suggesting the strong uptake of these AuNCs. The fluorescence intensity of AuNCs in L929 cells, upon normalized by their QY, was further quantitatively analyzed, which followed the order: AuNCs-3 > AuNCs-2 > AuNCs-1 > AuNCs-0, as shown in Fig. 5B. This observation is in good consistency with the cell uptake rate measured by ICP-OES in Fig. 4F, further supporting the distinct role of selenolate ligands on the cellular uptake of AuNCs [42]. Moreover, the cell imaging of these AuNCs in B16F10 cells was also investigated. As shown in Fig. S2 (Supporting information), similar as that in L929 cells, AuNCs with PhSeH as the co-stabilized ligands exhibited strong fluorescence signals in live B16 cells. Quantitative analysis of confocal images also showed a similar trend, where the normalized intensity of AuNCs in L929 cells increases as the PhSeH content of AuNCs raises (Fig. 5C). Altogether, these results suggest the great potential of selenolate ligands as stabilizers for developing robust fluorescent nanoprobes towards biological applications, such as imaging and sensing.

  Figure 5

  

  Figure 5.  (A) Bright field (upper), fluorescence (middle) and merged (lower) images of L929 cells upon incubation with different AuNCs (100 µg/mL) for 2 h. Normalized intensity per cell area of different AuNCs in (B) L929 cells and (C) B16F10 cells based on confocal images. All data are presented as mean ± SD (n = 3). *P < 0.05, **P < 0.01.

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  In summary, we report the synthesis of selenolate-costabilized water-soluble, NIR fluorescent AuNCs by a one-step reduction method. Our studies showed that the PhSeH content on the surface of AuNCs plays a crucial part in regulating their luminescence properties, stability and imaging property. It is discovered that AuNCs with an appropriate PhSeH content have the maximum emission intensity due to the LMCT effect, and using selenolate ligands instead of thiolate ligands can increase the photostability and long-term stability of AuNCs as a result of forming Au-Se bond. Moreover, differences in the amount of selenolate ligands of AuNCs can also affect their cellular uptake efficiency and further influence the imaging property. Taken together, these results provide new design guidelines for developing novel high-performance fluorescent AuNC probes, which also offer important approaches for advancing the biological applications of selenolate ligand-protected metal NCs.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Wanxin Li: Writing – original draft, Methodology, Investigation, Conceptualization. Wenxing Gao: Resources, Investigation. Mengyao Wen: Resources. Zecheng He: Resources. Li Shang: Writing – review & editing, Supervision, Funding acquisition, Conceptualization.

  Acknowledgments

  The authors acknowledge support from the National Natural Science Foundation of China (No. 22274131) and Shaanxi Fundamental Science Research Project for Chemistry & Biology (No. 22JHQ071).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110803.

  
  
• 1. [1]

     H.B. Lin, X.R. Song, O.J.H. Chai, et al., Adv. Mater. 36 (2024) 2401002. doi: 10.1002/adma.202401002

  2. [2]

     R.R. Nasaruddin, T.K. Chen, N. Yan, J.P. Xie, Coord. Chem. Rev. 368 (2018) 60–79. doi: 10.1016/j.ccr.2018.04.016

  3. [3]

     W.Q. Shi, L.L. Zeng, R.L. He, et al., Science 383 (2024) 326–330. doi: 10.1126/science.adk6628

  4. [4]

     N.M. Carigga Gutierrez, T.L. Clainche, A.L. Bulin, et al., Adv. Mater. 36 (2024) 2404605. doi: 10.1002/adma.202404605

  5. [5]

     M.J. Chao, S.M. Tai, M.X. Mao, et al., Aggregate 6 (2025) e644. doi: 10.1002/agt2.644

  6. [6]

     X.D. Lai, T.F. Liu, Z.C. Guo, et al., Chin. Chem. Lett. 36 (2025) 109762. doi: 10.1016/j.cclet.2024.109762

  7. [7]

     X.M. Zhou, X.J. Wang, L. Shang, Chin. Chem. Lett. 34 (2023) 108093. doi: 10.1016/j.cclet.2022.108093

  8. [8]

     W.B. Tseng, C.H. Hsu, M. Madhu, C.Y. Lu, W.L. Tseng, Chem. Eng. J. 498 (2024) 155133. doi: 10.1016/j.cej.2024.155133

  9. [9]

     J.Y. Sun, J.Y. Li, X. Li, et al., Chin. Chem. Lett. 34 (2023) 107891. doi: 10.1016/j.cclet.2022.107891

  10. [10]

      B.H. Zhang, J.S. Chen, Y.T. Cao, O.J.H. Chai, J.P. Xie, Small 17 (2021) 2004381. doi: 10.1002/smll.202004381

  11. [11]

      C.Y. Liu, Y. Pei, H. Sun, J. Ma, J. Am. Chem. Soc. 137 (2015) 15809–15816. doi: 10.1021/jacs.5b09466

  12. [12]

      W.N. Dong, F.J. Zhang, T.T. Li, et al., J. Am. Chem. Soc. 146 (2024) 22180–22192. doi: 10.1021/jacs.4c01291

  13. [13]

      X.K. Wan, J.Q. Wang, Z.A. Nan, Q.M. Wang, Sci. Adv. 3 (2017) e1701823. doi: 10.1126/sciadv.1701823

  14. [14]

      A. Cirri, H.M. Hernández, C. Kmiotek, C.J. Johnson, Angew. Chem. Int. Ed. 58 (2019) 13818–13822. doi: 10.1002/anie.201907586

  15. [15]

      X.F. Jiang, X.Y. Wang, C. Yao, et al., J. Phys. Chem. Lett. 10 (2019) 5237–5243. doi: 10.1021/acs.jpclett.9b02046

  16. [16]

      H. Tang, Q.Z. Li, W.X. Yan, X.Y. Jiang, Angew. Chem. Int. Ed. 60 (2021) 13829–13834. doi: 10.1002/anie.202101609

  17. [17]

      K.Y. Zheng, M.I. Setyawati, D.T. Leong, J.P. Xie, Chem. Mater. 30 (2018) 2800–2808. doi: 10.1021/acs.chemmater.8b00667

  18. [18]

      D. Yang, Y.T. Wu, Z.T. Yuan, et al., Sci. China Chem. 67 (2024) 806–823. doi: 10.1007/s11426-023-1851-9

  19. [19]

      X. Kang, M.Z. Zhu, Small 15 (2019) 1902703. doi: 10.1002/smll.201902703

  20. [20]

      C.K. Yee, A. Ulman, J.D. Ruiz, et al., Langmuir 19 (2003) 9450–9458. doi: 10.1021/la020628i

  21. [21]

      F.K. Huang, R.C. Horton, D.C. Myles, R.L. Garrell, Langmuir 14 (1998) 4802–4808. doi: 10.1021/la980263v

  22. [22]

      Y.B. Song, T.T. Cao, H.J. Deng, et al., Sci. China Chem. 57 (2014) 1218–1224. doi: 10.1007/s11426-014-5071-5

  23. [23]

      Y. Negishi, W. Kurashige, U. Kamimura, Langmuir 27 (2011) 12289–12292. doi: 10.1021/la203301p

  24. [24]

      W. Kurashige, M. Yamaguchi, K. Nobusada, Y. Negishi, J. Phys. Chem. Lett. 3 (2012) 2649–2652. doi: 10.1021/jz301191t

  25. [25]

      B. Hu, F.P. Kong, X.N. Gao, et al., Angew. Chem. Int. Ed. 57 (2018) 5306–5309. doi: 10.1002/anie.201712921

  26. [26]

      B. Hu, R.R. Cheng, X.J. Liu, et al., Biomaterials 92 (2016) 81–89. doi: 10.1016/j.biomaterials.2016.03.030

  27. [27]

      L.D. Geoffrion, T. Hesabizadeh, D. Medina-Cruz, et al., ACS Omega 5 (2020) 2660–2669. doi: 10.1021/acsomega.9b03172

  28. [28]

      J.P. Wang, M.K. Chen, Z.Y. Zhang, L. Ma, T.F. Chen, Coord. Chem. Rev. 493 (2023) 215278. doi: 10.1016/j.ccr.2023.215278

  29. [29]

      L. Wang, W.F. Zheng, X.J. Jiang, Chem. Commun. 56 (2020) 6664–6667. doi: 10.1039/d0cc02077j

  30. [30]

      Q. Li, M. Zhou, W.Y. So, et al., J. Am. Chem. Soc. 141 (2019) 5314–5325. doi: 10.1021/jacs.8b13558

  31. [31]

      J. Zheng, C. Zhou, M.X. Yu, J.B. Liu, Nanoscale 4 (2012) 4073–4082. doi: 10.1039/c2nr31192e

  32. [32]

      Z.K. Wu, R.C. Jin, Nano Lett. 10 (2010) 2568–2573. doi: 10.1021/nl101225f

  33. [33]

      J.M. Forward, D. Bohmann, J.P. Fackler, R.J. Staples, Inorg. Chem. 34 (1995) 6330–6336. doi: 10.1021/ic00129a019

  34. [34]

      J. Xu, J.M. Li, W.C. Zhong, et al., Chin. Chem. Lett. 32 (2021) 2390–2394. doi: 10.1016/j.cclet.2021.02.037

  35. [35]

      Z.N. Wu, Q.F. Yao, O.J.H. Chai, et al., Angew. Chem. Int. Ed. 59 (2020) 9934–9939. doi: 10.1002/anie.201916675

  36. [36]

      L. Shang, F. Stockmar, N. Azadfar, G.U. Nienhaus, Angew. Chem. Int. Ed. 52 (2013) 11154–11157. doi: 10.1002/anie.201306366

  37. [37]

      Y. Negishi, K. Nobusada, T. Tsukuda, J. Am. Chem. Soc. 127 (2005) 5261–5270. doi: 10.1021/ja042218h

  38. [38]

      Q. Li, X.M. Zhou, L.L. Tan, L. Shang, Sens. Actuators B: Chem. 385 (2023) 133695. doi: 10.1016/j.snb.2023.133695

  39. [39]

      J. Jiang, C.V. Conroy, M.M. Kvetny, et al., J. Phys. Chem. C 118 (2014) 20680–20687. doi: 10.1021/jp5060217

  40. [40]

      D. Radomska, R. Czarnomysy, D. Radomski, K. Bielawski, Int. J. Mol. Sci. 22 (2021) 1009–1035. doi: 10.3390/ijms22031009

  41. [41]

      S. Patil, A. Sandberg, E. Heckert, W. Self, S. Seal, Biomaterials 28 (2007) 4600–4607. doi: 10.1016/j.biomaterials.2007.07.029

  42. [42]

      K.Q. Liang, W.C. Zhong, M.Y. Wei, L.L. Tan, L. Shang, Anal. Chem. 95 (2023) 8077–8087. doi: 10.1021/acs.analchem.3c01077

• 

  Scheme1  Schematic illustration of the synthesis of AuNCs with different PhSeH contents.

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  Figure 1  TEM images of AuNCs-0 (A), AuNCs-1 (B), AuNCs-2 (C) and AuNCs-3 (D). Insets are the size histograms of AuNCs based on TEM images.

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  Figure 2  (A) Ultraviolet-visible absorption and fluorescence emission spectra of different AuNCs in aqueous solution. Excitation wavelength: 400 nm. 3D fluorescence spectra of AuNCs-0 (B), AuNCs-1 (C), AuNCs-2 (D) and AuNCs-3 (E). (F) Photoluminescence decay profiles of different AuNCs in aqueous solution and the fitting results. Excitation wavelength: 405 nm.

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  Figure 3  (A) XPS spectra of Au 4f in different AuNCs, and (B) the fraction of Au(Ⅰ) based on XPS data fitting. XPS spectra of S 2p (C) and Se 3d (D) in different AuNCs and the fitting results. All data are presented as mean ± standard deviation (SD) (n = 3).

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  Figure 4  (A) Time-dependent fluorescence intensity change of different AuNCs at 820 nm under UV irradiation. (B) Fluorescence stability of different AuNCs after storage in aqueous solution for different days. (C) Fluorescence stability of different AuNCs in the solution with different pH. The cell viability of (D) L929 cells and (E) B16F10 cells upon being incubated with four types of AuNCs at different concentrations. (F) Uptake efficiency of different AuNCs by L929 and B16F10 cells based on ICP-OES measurements. All data are presented as mean ± SD (n = 3). *P < 0.05, **P < 0.01.

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  Figure 5  (A) Bright field (upper), fluorescence (middle) and merged (lower) images of L929 cells upon incubation with different AuNCs (100 µg/mL) for 2 h. Normalized intensity per cell area of different AuNCs in (B) L929 cells and (C) B16F10 cells based on confocal images. All data are presented as mean ± SD (n = 3). *P < 0.05, **P < 0.01.

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  Table 1.  Summary of the characterization results of the physicochemical properties of different AuNCs.

  Property	AuNCs-0	AuNCs-1	AuNCs-2	AuNCs-3
  Core size (nm)	1.43 ± 0.02	1.58 ± 0.03	1.60 ± 0.02	1.59 ± 0.05
  Hydrodynamic size (nm)	2.9 ± 0.2	3.0 ± 0.3	3.7 ± 0.4	3.8 ± 0.4
  Zeta potential (mV)	−33.1 ± 0.2	−33.0 ± 1.7	−35.3 ± 0.4	−36.4 ± 0.3
  Se content (µg/mL)	0	7.96	10.34	15.50
  Emission maximum (nm)	816	816	818	820
  Quantum yield (%)	0.8	2.2	3.1	2.5
  Fluorescence lifetime (µs)	2.20 ± 0.06	3.56 ± 0.12	3.95 ± 0.06	3.62 ± 0.08

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