Six-photon upconverted excitation energy lock-in for ultraviolet-C enhancement

Photon upconversion of near-infrared (NIR) irradiation into ultraviolet-C (UVC) emission offers many exciting opportunities for drug release in deep tissues, photodynamic therapy, solid-state lasing, energy storage, and photocatalysis. However, NIR-to-UVC upconversion remains a daunting challenge due to low quantum efficiency. Here, we report an unusual six-photon upconversion process in Gd3+/Tm3+-codoped nanoparticles following a heterogeneous core-multishell architecture. This design efficiently suppresses energy consumption induced by interior energy traps, maximizes cascade sensitizations of the NIR excitation, and promotes upconverted UVC emission from high-lying excited states. We realized the intense six-photon-upconverted UV emissions at 253 nm under 808 nm excitation. This work provides insight into mechanistic understanding of the upconversion process within the heterogeneous architecture, while offering exciting opportunities for developing nanoscale UVC emitters that can be remotely controlled through deep tissues upon NIR illumination.

Energy Transfer Between Yb3+- Mn2+ in Zn(Po3 ) 2 Glasses Giving Green, Red and Infrared Light

The Yb3+-Mn2+codoped zinc metaphosphate glass gives rise to several processes such as upconversion, downshifting and double ion absorptions producing light from the visible to the IR wavelengths. These processes are possible since the Mn2+ and the Yb3+ ions replaces the Zn2+ ion in nanoparticles of the α phase of the compound Zn(PO3)2. An important result is that the α structure presence allows the formation of Yb3+-Mn2+ dimers, that gives rise to a superexchange coupling that allows an upconversion process from the IR to the red region of the electromagnetic spectrum. The experimental results also show that these dimers can couple to produce Yb3+ ion pairs that led to a cooperative emission in the green, around 500nm, coupling also the Mn2+ ions that in turn allows to produce a double absorption of this ions in the red region of the electromagnetic spectrum and as well a downshifting process conducting to the Yb3+ emission in the infrared. If the manganese ion concentration is higher than 10% most of these effects are masked. All these results make the material an effective option for different applications, due to the large wavelength variety that can be selected for excitation or emission

Energy Transfer Between Yb3+- Mn2+ in Zn(Po3 ) 2 Glasses Giving Green, Red and Infrared Light

The Yb3+-Mn2+codoped zinc metaphosphate glass gives rise to several processes such as upconversion, downshifting and double ion absorptions producing light from the visible to the IR wavelengths. These processes are possible since the Mn2+ and the Yb3+ ions replaces the Zn2+ ion in nanoparticles of the α phase of the compound Zn(PO3)2. An important result is that the α structure presence allows the formation of Yb3+-Mn2+ dimers, that gives rise to a superexchange coupling that allows an upconversion process from the IR to the red region of the electromagnetic spectrum. The experimental results also show that these dimers can couple to produce Yb3+ ion pairs that led to a cooperative emission in the green, around 500nm, coupling also the Mn2+ ions that in turn allows to produce a double absorption of this ions in the red region of the electromagnetic spectrum and as well a downshifting process conducting to the Yb3+ emission in the infrared. If the manganese ion concentration is higher than 10% most of these effects are masked. All these results make the material an effective option for different applications, due to the large wavelength variety that can be selected for excitation or emission.

Upconverted excitation energy lock-in for deep-ultraviolet enhancement

Photon upconversion of near-infrared (NIR) irradiation into deep-ultraviolet (UV) emission offers many exciting opportunities for drug release in deep tissues, photodynamic therapy, solid-state lasing, energy storage, and photocatalysis. However, NIR-to-deep-UV upconversion remains a daunting challenge due to low quantum efficiency. Here, we report an unusual six-photon upconversion process in Gd3+/Tm3+-codoped nanoparticles comprising a heterogeneous, core-multishell nanostructure. This multishell design efficiently suppresses energy consumption induced by interior energy traps, maximizes cascade sensitizations of the NIR excitation, and promotes upconverted deep-UV emission from high-lying excited states. We released the intense six-photon-upconverted UV emissions at 253 nm under 808-nm excitation. This work provides new insight into mechanistic understanding of the upconversion process within the heterogeneous architecture, while offering exciting opportunities for developing nanoscale deep-UV emitters that can be remotely controlled in deep tissues upon NIR illumination.

Sum Squeezing of the Field Amplitude in Frequency Upconversion Process

Sum squeezing of the field amplitude is studied in the nondegenerate and degenerate frequency upconversion process under the short interaction time. It is shown that sum squeezing can be converted into normal squeezing via sum-frequency generation in the nondegenerate frequency upconversion process, while the amplitude-squared squeezing of the fundamental mode directly changed into the squeezing of the harmonic in the degenerate frequency upconversion process. All reachable conditions of uncorrelated modes for obtaining a sum squeezing in two modes and its dependence on the squeezing of individual field modes are investigated. It is found that the squeezed states are associated with large number of pump photons. It is also confirmed that the higher-order squeezing (sum squeezing) is directly associated with coupling of the field and interaction time.

Yb3+/Er3+ co-doped Dion–Jacobson niobium layered perovskites as NIR-to-green upconversion materials

Low-phonon lanthanide-doped layered niobate materials generated efficient green upconversion luminescence. The low defect concentration near the emitting centres favoured the upconversion process.