In this study, spinel-phase ZnGaGeO (ZGO:Ge) ( = 0–0.90) and ZnGaHfGeO:Cr (ZGGO:Cr,Hf) ( = 0–0.075) nanoparticles were prepared by a hydrothermal method combined with a subsequent vacuum annealing. For Crdoped ZGO:Ge nanoparticles, it was found that the replacement of Ga with high-valence Ge can lead to more uniform morphology and enhanced afterglow. Meanwhile, for ZGGO:Cr,Hf nanoparticles, the non-equivalent replacement of Ga with high-valence Hf can give rise to the decrease in standard deviation gradually from 12.3 to 7.0 nm and the afterglow intensity is increased to 3.4 times of the undoped ZGGO:Cr nanoparticles. Based on the first principle calculations using an ideal model of ZnGaO (ZGO) unit, it is found that the formation energy (11.32 eV) using a doped model of ZnGaGeO unit (i.e. three Ge ions substitute for three Ga ions and one Ga vacancy (V′′′) is created in a unit due to the charge compensation effect) is lower than that (13.35 eV) using a doped model of ZnGaGeO unit (i.e. three Ge ions and three Zn ions substitute for six Ga ions without the charge compensation effect). Combined with the spectral data, we can confirm that, in the case of the same Ge doping concentration ( = 0.75), the formula of ZGGO host is ZnGaGeO rather than ZnGaGeO. Based on the above ZGGO (ZnGaGeO) model, it is found that the smaller formation energies (−1.49 to −3.34 eV) of the Hf doped systems further prove that high-valence Hf ions prefer to substitute for octahedral and tetrahedral Ga and Ge sites and promote the creation of Zn’–Ga° and Ga° defects and it leads to the improved afterglow. Furthermore, contrary to other isovalent ions (such as Nd) doped ZGGO nanoparticles, ZGGO:Cr,Hf nanoparticles exhibit excellent dispersion stability in an acidic fluid. These findings suggest ZGGO:Cr,Hf nanoparticles might be potential for bioimaging in an acidic body fluid.

中文翻译：

---

通过高价离子掺杂优化 Zn2Ga2.98-4x/3HfxGe0.75O8:Cr0.02 纳米粒子的尺寸分布和近红外持久发光

在本研究中，通过水热法结合随后的真空退火制备了尖晶石相 ZnGaGeO (ZGO:Ge) (= 0–0.90) 和 ZnGaHfGeO:Cr (ZGGO:Cr,Hf) (= 0–0.075) 纳米颗粒。对于Cr掺杂的ZGO:Ge纳米粒子，发现用高价Ge替代Ga可以导致更均匀的形貌和增强的余辉。同时，对于ZGGO:Cr,Hf纳米粒子，高价Hf非等价替代Ga可使标准差从12.3 nm逐渐减小至7.0 nm，余辉强度增加至未掺杂ZGGO的3.4倍：Cr纳米颗粒。基于ZnGaO（ZGO）单元理想模型的第一性原理计算，发现ZnGaGeO单元掺杂模型（即三个Ge离子替代三个Ga离子和一个Ga空位）的形成能（11.32 eV）（由于电荷补偿效应，单元中产生的 V'''）低于使用 ZnGaGeO 单元的掺杂模型（即三个 Ge 离子和三个 Zn 离子替代 6 个 Ga 离子，无需电荷补偿）的值 (13.35 eV)影响）。结合光谱数据，我们可以确认，在Ge掺杂浓度相同（=0.75）的情况下，ZGGO基质的分子式是ZnGaGeO而不是ZnGaGeO。基于上述ZGGO（ZnGaGeO）模型，发现Hf掺杂体系较小的形成能（-1.49至-3.34 eV）进一步证明高价Hf离子更倾向于取代八面体和四面体Ga和Ge位点并促进Zn'–Ga°和Ga°缺陷的产生，从而改善余辉。此外，与其他等价离子（例如Nd）掺杂的ZGGO纳米粒子相反，ZGGO:Cr,Hf纳米粒子在酸性流体中表现出优异的分散稳定性。这些发现表明 ZGGO:Cr,Hf 纳米颗粒可能具有在酸性体液中进行生物成像的潜力。