Ultrasensitive Detection of <i>Shigella</i> Species in Blood and Stool

A modified immunosensing system with voltage-controlled signal amplification was used to detect <i>Shigella</i> in stool and blood matrixes at the single-digit CFU level. Inactivated <i>Shigella</i> was spiked in these matrixes and detected directly. The detection was completed in 78 min. Detection limits of 21 CFU/mL and 18 CFU/mL were achieved in stool and blood, respectively, corresponding to 2–7 CFUs immobilized on the detecting electrode. The outcome of the detection of extremely low bacterium concentration, i.e., below 100 CFU/mL, blood samples show a random nature. An analysis of the detection probabilities indicates the correlation between the sample volume and the success of detection and suggests that sample volume is critical for ultrasensitive detection of bacteria. The calculated detection limit is qualitatively in agreement with the empirically determined detection limit. The demonstrated ultrasensitive detection of <i>Shigella</i> on the single-digit CFU level suggests the feasibility of the direct detection of the bacterium in the samples without performing a culture

Improvement of Green Upconversion Monochromaticity by Doping Eu³⁺ in Lu₂O₃:Yb³⁺/Ho³⁺ Powders with Detailed Investigation of the Energy Transfer Mechanism

The monochromaticity improvement of green upconversion (UC) in Lu₂O₃:Yb³⁺/Ho³⁺ powders has been successfully realized by tridoping Eu³⁺. The integral area ratio of green emission to red emission of Ho³⁺ increases 4.3 times with increasing Eu³⁺ doping concentration from 0 to 20 mol %. The energy transfer (ET) mechanism in the Yb³⁺/Ho³⁺/Eu³⁺ tridoping system has been investigated carefully by visible and near-infrared (NIR) emission spectra along with the decay curves, revealing the existence of ET from the Ho³⁺ ⁵F₄/⁵S₂ level tothe Eu³⁺ ⁵D₀ level and ET from the Ho³⁺ ⁵I₆ level to the Eu³⁺ ⁷F₆ level. In addition, the population routes of the red-emitting Ho³⁺ ⁵F₅ level in the Yb³⁺/Ho³⁺ codoped system under 980 nm wavelength excitation have also been explored. The ET process from the Yb³⁺ ²F_5/2 level to the Ho³⁺ ⁵I₇ level and the cross-relaxation process between two nearby Ho³⁺ ions in the ⁵F₄/⁵S₂ level and ⁵I₇ level, respectively, have been demonstrated to be the dominant approaches for populating the Ho³⁺ ⁵F₅ level. The multiphonon relaxation process originating from the Ho³⁺ ⁵F₄/⁵S₂ level is useless to populate the Ho³⁺ ⁵F₅ level. As the energy level gap between the Ho³⁺ ⁵I₇ level and Ho³⁺ ⁵I₈ level matches well with that between Eu³⁺ ⁷F₆ level and Eu³⁺ ⁷F₀ level, the energy of the Ho³⁺ ⁵I₇ level can be easily transferred to the Eu³⁺ ⁷F₆ level by an approximate resonant ET process, resulting in a serious decrease in the red UC emission intensity. Since this ET process is more efficient than the ET from the Ho³⁺ ⁵F₄/⁵S₂ level to the Eu³⁺ ⁵D₀ level as well as the ET from the Ho³⁺ ⁵I₆ level to the Eu³⁺ ⁷F₆ level, the integral area ratio of green emission to red emission of Ho³⁺ has been improved significantly

Enhancement of Eu³⁺ Red Upconversion in Lu₂O₃: Yb³⁺/Eu³⁺ Powders under the Assistance of Bridging Function Originated from Ho³⁺ Tridoping

The red upconversion (UC) emission of Eu³⁺ ions in Lu₂O₃: Yb³⁺/Eu³⁺ powders was successfully enhanced by tridoping Ho³⁺ ions in the matrix, which is due to the bridging function of Ho³⁺ ions. The experiment data manifest that, in Yb³⁺/Eu³⁺/Ho³⁺ tridoped system, the Ho³⁺ ions are first populated to the green emitting level ⁵F₄/⁵S₂ through the energy transfer (ET) processes from the excited Yb³⁺ ions. Subsequently, the Ho³⁺ ions at ⁵F₄/⁵S₂ level can transfer their energy to the Eu³⁺ ions at the ground state, resulting in the population of Eu³⁺ ⁵D₀ level. With the assistance of the bridging function of Ho³⁺ ion, this ET process is more efficient than the cooperative sensitization process between Yb³⁺ ion and Eu³⁺ ion. Compared with Lu₂O₃: 5 mol % Yb³⁺/1 mol % Eu³⁺, the UC intensity of Eu³⁺ ⁵D₀→⁷F₂ transition in Lu₂O₃: 5 mol % Yb³⁺/1 mol % Eu³⁺/0.5 mol % Ho³⁺ is increased by a factor of 8

Stacking faults enabled second harmonic generation in centrosymmetric van der Waals RhI3

Second harmonic generation (SHG) in van der Waals (vdWs) materials has garnered significant attention due to its potential for integrated nonlinear optical and optoelectronic applications. Stacking faults in vdWs materials, a typical kind of planar defect, can introduce a new degree of freedom to modulate the crystal symmetry and resultant SHG response, however, the physical origin and tunability of stacking-fault-governed SHG in vdWs materials remain unclear. Here, taking the intrinsically centrosymmetric vdWs RhI3 as an example, we theoretically reveal the origin of stacking-fault-governed SHG response, where the SHG response comes from the energetically favorable AC- Cstacking fault of which the electrical transitions along the high symmetry paths Gamma-M and Gamma-K in the Brillion zone play the dominant role at 810 nm. Such stacking-fault-governed SHG response is further confirmed via structural characterizations and SHG measurements. Furthermore, by applying hydrostatic pressure on RhI3, the correlation between structural evolution and SHG response is revealed with SHG enhancement up to 6.9 times, where the decreased electronic transition energies and huger momentum matrix elements due to the stronger interlayer interactions upon compression magnify the SHG susceptibility. This study develops a promising foundation based on strategically designed stacking faults for pioneering new avenues in nonlinear nano-optics