Key Takeaways & Executive Findings
- •• Two-dimensional (2D) TiO2 was developed with >99% visible light transmittance for non-whitening UV protection, outperforming conventional 0D TiO2 in aesthetics while matching UV-blocking efficacy. • 2D TiO2 achieves ultralow skin penetration and 90% reduced reactive oxygen species generation versus 0D TiO2, eliminating photocatalytic toxicity and DNA damage risks. • 2D TiO2 enabled tunable UVA/UVB coverage via metal doping without compromising visible light transmittance, ensuring Scientific Committee on Consumer Safety compliance and biocompatibility. • We integrated high UV protection, natural appearance, and photoinertness into a single material, redefining aesthetic-safe sunscreen design through 2D structural innovation.
Abstract
Titanium dioxide (TiO2) has been an important protective ingredient in mineral-based sunscreens since the 1990s. However, traditional TiO2 nanoparticle formulations have seen little improvement over the past decades and continue to face persistent challenges related to light transmission, biosafety, and visual appearance. Here, we report the discovery of two-dimensional (2D) TiO2, characterized by a micro-sized lateral dimension (~1.6 μm) and atomic-scale thickness, which fundamentally resolves these long-standing issues. The 2D structure enables exceptional light management, achieving 80% visible light transparency—rendering it nearly invisible on the skin—while maintaining UV-blocking performance comparable to unmodified rutile TiO2 nanoparticles. Its larger lateral size results in a two-orders-of-magnitude reduction in skin penetration (0.96 w/w%), significantly enhancing biosafety. Moreover, the unique layered architecture inherently suppresses the generation of reactive oxygen species (ROS) under sunlight exposure, reducing the ROS generation rate by 50-fold compared to traditional TiO2 nanoparticles. Through precise metal element modulation, we further developed the first customizable sunscreen material capable of tuning UV protection ranges and automatically matching diverse skin tones. The 2D TiO2 offers a potentially transformative approach to modern sunscreen formulation, combining superior UV protection, enhanced safety and a natural appearance.
1. Introduction
Skin cancer is a significant threat to human health. As reported in a World Health Organization report in 2020, there are over 1.5 million annual diagnosed cases of skin cancer worldwide, with approximately 8% of patients experiencing a fatal outcome [1]. Excessive exposure to ultraviolet (UV) radiation stands as the foremost cause, contributed to more than 90% of all skin cancer cases [2]. Human efforts to shield against UV radiation date back to ancient times. For instance, ancient Egyptians used natural jasmine oil and rice bran to shield their skin from UV damage [3]. With advances in optics and physiology during the twentieth century, systematic investigations on the effects of UV exposure on human skin were started, leading to rapid progress in the use of active ingredients for UV blocking. One of the significant milestones occurred in 1928 with the introduction of sunscreen containing salicylates and cinnamates as effective components [4]. Until 1969, avobenzone, capable of shielding against ultraviolet radiation A (UVA) in the 320–400 spectral range, was developed [5]. To date, the US Food and Drug Administration and European Commission certified sunscreens use mostly organic compounds, which are considered indispensable [6]. However, these organic UV-blocking additives are prone to degradation and loss of efficacy during photoactivation [7]. For instance, avobenzone can lose 36% of its absorption capacity after one hour of sunlight exposure [8]. Moreover, some organic additives can either penetrate the skin or cause potential skin sensitization in clinical settings [9–11].
Nowadays, inorganic titanium dioxide (TiO2) was gradually proposed to replace organic additives in sunscreen formulations because of its outstanding UV stability and efficient UV shielding ability [12, 13]. This significantly prolonged the UV protection time and facilitated the rise of physical sunscreen ingredients [14, 15]. Consequently, inorganic based sunscreens have gained significant market share in recent years [16]. TiO2 primarily exists in two crystalline phases: rutile and anatase. The anatase phase exhibits stronger phototoxicity due to its significantly distorted octahedra and is commonly utilized as a photocatalytic material [17–21], whereas the rutile phase, with higher symmetry, demonstrates reduced phototoxicity. In accordance with the Scientific Committee on Consumer Safety guidelines [22], current physical sunscreens predominantly utilize rutile-phase TiO2 particles in the nanometer range (>30 nm). Current p
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Ruoning Yang, Jiefu Chen, Xiang Li, Yaxin Zhang, Baofu Ding, Yujiangsheng Xu, Shaoqiang Luo, Shaohua Ma, Xingang Ren, Gang Liu, Ling Qiu, Hui-Ming Cheng (2025). Two-Dimensional TiO2 Ultraviolet Filters for Sunscreens. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01805-1
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Frequently Asked Questions
What is the main advantage of 2D TiO2 over traditional TiO2 nanoparticles in sunscreens?
2D TiO2 offers significantly higher visible light transparency (80% vs. lower for nanoparticles), reducing the whitening effect on skin, while maintaining comparable UV-blocking efficacy. It also exhibits much lower skin penetration and reduced reactive oxygen species generation, enhancing biosafety.
How does 2D TiO2 improve skin safety?
The larger lateral size of 2D TiO2 reduces skin penetration by two orders of magnitude compared to nanoparticles, and its layered structure suppresses ROS generation by 50-fold, minimizing photocatalytic toxicity and DNA damage risks.
Can 2D TiO2 be customized for different skin tones?
Yes, through precise metal element modulation, 2D TiO2 can be engineered to tune UV protection ranges and automatically match diverse skin tones, offering a customizable sunscreen material.
What is the significance of the 2D structure in UV protection?
The 2D structure enables exceptional light management, achieving high visible light transparency while maintaining UV-blocking performance, and inherently suppresses ROS generation, addressing long-standing issues of traditional TiO2 nanoparticles.
Is 2D TiO2 compliant with safety regulations?
The study indicates that 2D TiO2 can be tuned via metal doping to ensure compliance with Scientific Committee on Consumer Safety guidelines and biocompatibility, making it suitable for sunscreen applications.
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