Ultra-flexible and highly sensitive scintillation screen based on perovskite quantum dots for non-flat objects X-ray imaging

https://doi.org/10.1016/j.mtphys.2021.100390Get rights and content

Highlights

  • Polymer-Perovskite QDs-Polymer sandwich structure scintillation screen has been synthesized with a simply spin-coated method.

  • Polymer-Perovskite QDs-Polymer thin film exhibits ultra-flexible.

  • Polymer-Perovskite QDs-Polymer thin film exhibits the high sensitivity, fast response and stable to X-ray.

  • High-resolution X-ray imaging is achieved for non-flat objects.

Abstract

A flexible and highly sensitive scintillation screen is urgently expected for X-ray imaging technology, especially for non-flat, flexible objects in medical and industrial applications. Here, we report a sandwich structure of polymer-perovskite quantum dots-polymer (PPP) scintillation screen. The outer polymer layer provides high mechanical stability and encapsulation for the internal perovskite quantum dots active layer. The relative light output remains 93 ± 0.5% of its initial value after bending cycles up to 600 with a bending radius down to 2.5 mm. This PPP scintillation screen exhibits ultra-sensitivity to low energy X-ray with a detection limit of 1.57nGyair/s and fast decay time of 63.7ns. Well-resolved X-ray images are recorded with a common digital camera with a spatial resolution of 5.35 lp/mm at MTF = 0.3 under the exposure dose of 12 μGyair, which is much lower than the requirement of medical applications. These features demonstrate that this flexible scintillation screen can be applied for non-flat X-ray imaging applications under low-dose X-ray exposure.

Introduction

X-ray imaging technology enables the examination of an object’s internal information, which has wide applications including medical diagnostics, non-destructive testing, scientific research, and home security inspection [[1], [2], [3], [4], [5], [6], [7], [8], [9], [10]]. Currently, both indirect-conversion method and direct-conversion method have been developed to achieve high contrast X-ray imaging [[11], [12], [13], [14], [15], [16]]. The indirect-conversion method consists of scintillators (convert the X-ray to UV–Visible photons) and high sensitivity photodetector [[11], [12], [13]]. The other direct-conversion method utilizes a semiconductor material including amorphous Se (α-Se), PbI2, HgI2, and CdZnTe to directly convert the X-ray to electrical signals [[14], [15], [16]]. Recently, a series of materials such as organic-inorganic and all-inorganic perovskite thin film and single crystals have been demonstrated with high sensitivity for X-ray detection, which enables to provide low-dose X-ray imaging [[17], [18], [19], [20], [21], [22], [23], [24], [25]]. However, the X-ray imaging based on these traditional flat detector technologies could not perfectly satisfy the requirement for non-flat, flexible objects imaging, especially in medical and industry applications [[26], [27], [28], [29], [30]].

Currently, several strategies have been proposed to achieve a flexible X-ray detector. The dominant method is to deposite radiation-sensitive semiconductor materials (such as Ga2O3, indium-gallium-zinc-oxide, All-Inorganic Perovskite Quantum Dots) on the surfaces of flexible substrates [[31], [32], [33]]. These high performance flexible X-ray detectors suffer from poor bendability of the flexible substrates. Huang et al. has shown the perovskite-filled membranes based X-ray detector which achieves a small curvatures down to 2 mm [34]. However, one of the main obstacles limiting potential applications of these direct-conversion semiconductor detectors is the relatively low spatial resolution for X-ray imaging application. Despite enormous efforts to develop highly sensitive, and flexible X-ray detectors for imaging applications, the realization of X-ray imaging with high spatial resolution, high sensitivity, and flexibility is still needed to improve.

Nanoscale materials with high color purity, high quantum yield, and tunable emission have been demonstrated to be able to provide high spatial resolution X-ray imaging [2,3,35]. Here, we have designed a sandwich structure thin film scintillation screen that realizes high spatial resolution, high sensitivity, speed, large scale, flexible, and stable X-ray imaging with low cost. This sandwich structure thin film scintillation screen consists of two highly transparent thin polymer layer and an active perovskite quantum dots (QDs) layer. The polymer layer plays an important role in encapsulating protect, that to achieve high stability even immersing it into water. The active perovskite QDs layer is employed to convert the X-ray to visible photons. We have demonstrated that this flexible polymer-perovskite-polymer (PPP) scintillation screen is highly flexible, ultrasensitive to X-ray, which can be applied for low-dose X-ray imaging with high spatial resolution.

Section snippets

Designed structure

A flexible three-layer sandwich structural polymer-perovskite QDs-polymer (PPP) thin-film scintillation screen was synthesized by the spin coating method as shown in Fig. 1. Firstly, a thin layer of commercial polymer is spin-coated onto the quartz substrate. Then, monolayers of perovskite QDs are deposited on the top of the polymer as an active layer. The second layer of polymer is coated with the perovskite QDs thin film for encapsulating. Finally, peel off this flexible sandwich structural

Conclusion

In conclusion, we have developed a highly sensitive, flexible, fast scintillation screen with sandwich structural (polymer-perovskite QDs-polymer). The polymer shell layer can provide remarkable even fold in half flexibility, mechanical stability, and encapsulation for ultra air stability. The active perovskite QDs layer can be highly efficient and fast to convert the X-ray photons to visible photons. This flexible PPP scintillation screen presents high sensitivity, low detection limit, and

Synthesis of CH3NH3Br3 quantum dots

Before obtaining CH3NH3Br3 quantum dots, we have synthesized CH3NH3Br and C4H9NH3Br powder with a solution method. Both CH3NH3Br and C4H9NH3Br were synthesized by the reaction with a different molar ratio of methylamine and butylamine to HBr under an ice-water bath, respectively. The volume ratio of methylamine and butylamine to HBr is 57: 85 and 50:57, respectively. The obtained raw CH3NH3Br and C4H9NH3Br powder were washed using diethyl ether at least three times for purification and then

CRediT author statement

Qiang Xu: Writing draft, Conceptualization, Methodology, Validation, Data curation, Supervision,Writing - review & editing, Project administration conceived the idea and supervised the project. Shuai Zhou: Data curation, Investigation, Methodology. Jie Huang: Methodology, Data curation, Investigation. Xiao Ouyang: Data curation, Investigation. Jun Liu: Data curation. Yong Guo: Methodology. Juan Wang: Data curation. Jing Nie: Data curation. Xinlei Zhang: Data curation. Xiaoping Ouyang:

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.

Acknowledgments

This work was funded by the National Natural Science Foundation of China (Grants No. 11705090, 11875166, and 11435010).

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