The preferred upconversion pathway for the red emission of lanthanide-doped upconverting nanoparticles, NaYF4:Yb(3+),Er(3.).

Lanthanide-doped upconverting nanoparticles (UCNPs, NaYF4:Yb(3+),Er(3+)) are well known for emitting visible photons upon absorption of two or more near-infrared (NIR) photons through energy transfer from the sensitizer (Yb(3+)) to the activator (Er(3+)). Of the visible emission bands (two green and one red band), it has been suggested that the red emission results from two competing upconversion pathways where the non-radiative relaxation occurs after the second energy transfer (pathway A, (4)I15/2 → (4)I11/2 → (4)F7/2 → (2)H11/2 → (4)S3/2 → (4)F9/2 → (4)I15/2) or between the first and the second energy transfer (pathway B, (4)I15/2 → (4)I11/2 → (4)I13/2 → (4)F9/2 → (4)I15/2). However, there has been no clear evidence or thorough analysis of the partitioning between the two pathways. We examined the spectra, power dependence, and time profiles of UCNP emission at either 980 nm or 488 nm excitation, to address which pathway is preferred. It turned out that the pathway B is predominant for the red emission over a wide range of excitation powers.

Efficacy of ethyl ascorbyl ether-containing cosmetic cream on blue light-induced skin changes.

BACKGROUND: Office workers are consistently exposed to blue light, mainly from sunlight and digital device. Recent studies report that blue light has various harmful effects, including cellular changes via reactive oxygen species. Studies on blue light-induced skin changes have only been conducted in vitro and have not been clinically confirmed. OBJECTIVE: We provide novel methods to evaluate the effect of the product on the recovery of skin changed by blue light. METHODS: Internet surveys were conducted for workers in their 20s and 40s regarding exposure time to blue light in various environments. To study the effects of long-term exposure to blue light (456 nm) on the skin, we designed three light intensity conditions, and various skin characteristics were observed. After blue light irradiation, various skin characteristics were analyzed before and after applying ethyl ascorbyl ether (EAE)-containing cosmetic cream for 2 weeks. RESULTS: When exposed to strong blue light for approximately 16 days, the L* value, skin hydration, transparency, and elasticity decreased, and the melanin index, erythema index, a* value, and b* value increased. Furthermore, after short-term blue light irradiation (dose, 269 J/cm2 , the equivalent of blue light exposure for approximately 38 days in daily life), the L* value and elasticity decreased, and the melanin index and erythema index increased. However, when EAE cream was applied on skin for 1-2 weeks, the skin recovered. CONCLUSION: This study clinically confirms the skin changes caused by blue light and the effect of EAE in relieving such changes.

Clinical evaluation method for blue light (456 nm) protection of skin.

BACKGROUND: Blue light from electronic devices enriched with a peak at 456 nm affects circadian rhythm and antioxidant balance of skin, necessitating the study of photoprotection against the 456-nm blue light. AIMS: This study aims to report that blue light (456 nm) can cause skin pigmentation and proposes a new clinical evaluation method for blue light (456 nm) protection based on the skin pigmentation level. PATIENTS/METHODS: We developed a clinical device (ABC deviceTM ) that emits blue light (peak = 456 nm). Based on the minimal persistent pigment darkening dose (MPPD) determined from visual evaluation and melanin index measurements, we proposed the "protection grade of blue light (PB)" guideline to assess the protective ability of skin against blue light. RESULTS: Human skin irradiated with blue light (456 nm) showed a light dose-dependent degree of pigmentation. The MPPD on unprotected and protected skin was 135 J/cm2 or 180 J/cm2 and 135-225 J/cm2 , respectively. The ABC device™ and the proposed clinical method were used to test the four blue light blocking assessments of TiO2 . Consequently, the inorganic filter with TiO2 effectively blocked the blue light (456 nm). The AP product demonstrated the ability to block blue light by 1.15 times (PB = 1.15), which significantly lowered the melanin index of the skin after irradiation as compared to that of the unprotected skin (P < .001). CONCLUSION: We propose an objective clinical evaluation method for blue light protection. This study elucidates the properties of blue light blockers for customers suffering from blue light pollution.

Fast and background-free three-dimensional (3D) live-cell imaging with lanthanide-doped upconverting nanoparticles.

We report on the development of a three-dimensional (3D) live-cell imaging technique with high spatiotemporal resolution using lanthanide-doped upconverting nanoparticles (UCNPs). It employs the sectioning capability of confocal microscopy except that the two-dimensional (2D) section images are acquired by wide-field epi-fluorescence microscopy. Although epi-fluorescence images are contaminated with the out-of-focus background in general, the near-infrared (NIR) excitation used for the excitation of UCNPs does not generate any autofluorescence, which helps to lower the background. Moreover, the image blurring due to defocusing was naturally eliminated in the image reconstruction process. The 3D images were used to investigate the cellular dynamics such as nuclear uptake and single-particle tracking that require 3D description.