Temperature-dependent excitonic emission characteristics of highly crystallized carbon nitride nanosheets.

Highly-crystallized carbon nitride (HCCN) nanosheets exhibit significant potential for advancements in the field of photoelectric conversion. However, to fully exploit their potential, a thorough understanding of the fundamental excitonic photophysical processes is crucial. Here, the temperature-dependent excitonic photoluminescence (PL) of HCCN nanosheets and amorphous polymeric carbon nitride (PCN) is investigated using steady-state and time-resolved PL spectroscopy. The exciton binding energy of HCCN is determined to be 109.26 meV, lower than that of PCN (207.39 meV), which is attributed to the ordered stacking structure of HCCN with a weaker Coulomb interaction between electrons and holes. As the temperature increases, a noticeable reduction in PL lifetime is observed on both the HCCN and PCN, which is ascribed to the thermal activation of carrier trapping by the enhanced electron-phonon coupling effect. The thermal activation energy of HCCN is determined to be 102.9 meV, close to the value of PCN, due to their same band structures. Through wavelength-dependent PL dynamics analysis, we have identified the PL emission of HCCN as deriving from the transitions:σ*-LP,π*-π, andπ*-LP, where theπ*-LP transition dominants the emission because of the high excited state density of the LP state. These results demonstrate the impact of high-crystallinity on the excitonic emission of HCCN materials, thereby expanding their potential applications in the field of photoelectric conversion.

Synthesis of Fe Atom-Doped Monodisperse Co2P Nanorods with a Dual-Ligand Strategy for Excellent Electrocatalytic Hydrogen Evolution Performance.

Cobalt phosphide has been widely used in various catalytic reactions due to its excellent catalytic activity and stability. In contrast to the conventional synthesis of Co2P nanorods using expensive and toxic trioctylphosphine (TOP), this study employs a dual-ligand strategy to prepare iron-atom-doped monodisperse Co2P nanorods. The strategy involves the use of triphenylphosphite (TPOP) as a cost-effective and relatively less toxic strong ligand, alongside hexadecylamine (HDA) as a weaker ligand. The resultant atom-doped Co2P nanorods exhibited a large aspect ratio, providing a plentiful supply of active sites for electrocatalytic hydrogen evolution. In both alkaline and acidic electrolytes, achieving a current density of 10 mA cm-2 required overpotentials of 91 and 141 mV, respectively, with the optimal Co:Fe molar ratio of 1:0.2. The introduction of Fe atoms through doping increased the electron density at the Co atom sites, thereby enhancing H adsorption. This research offers a cost-effective and relatively low-toxicity method for the controlled fabrication of monodisperse transition-metal phosphide nanorods, enabling efficient catalytic reactions.

Efficacy and Safety of Second-line Treatments in Patients with Advanced Hepatocellular Carcinoma after Sorafenib Failure: A Meta-analysis.

BACKGROUND AND AIMS: In the last decade, several second-line therapies followed by sorafenib in patients with advanced hepatocellular carcinoma (HCC) have been reported. But the outcomes were different from each other. This meta-analysis aimed to evaluate the efficacy and safety of the second-line therapies followed by sorafenib in patients with advanced HCC. METHODS: Embase (1974 to October 2019) and Ovid MEDLINE (1946 to October 2019) were searched for randomized clinical trials on second-line therapies followed by sorafenib in patients with advanced HCC. The quality of each study was assessed by the modified Jadad scale. Statistical analysis was carried out by RevMan5.3 software. Efficacy and safety were analyzed. Efficacy included overall survival (OS), disease control rate, time to progression, and progression-free survival. RESULTS: Eight studies involving 3,173 patients were eligible. No difference in OS was found between the second-line treatment group and the control group (HR=0.87, 95% CI: 0.74-1.01, p=0.06). Disease control rate (relative risk (RR)=1.36, 95% CI: 1.16-1.60, p=0.0002), time to progression (HR=0.64, 95% CI: 0.51-0.81, p=0.0002) and progression-free survival (HR=0.60, 95% CI: 0.46-0.77, p<0.0001) were significantly improved by the second-line therapies. There was a slight difference in adverse events of any grade (RR=1.07, 95% CI: 1.00-1.14, p=0.03) between the two groups. CONCLUSIONS: These second-line therapies followed by sorafenib may potentially improve the prognosis in patients with advanced HCC. Compared with other second-line therapies, regorafenib seemed to be more effective.

The impact of neoadjuvant chemotherapy on low anterior resection syndrome after rectal cancer resection: A 6 Months longitudinal follow-up.

BACKGROUND/OBJECTIVE: Neoadjuvant radiotherapy plays a vital role in rectal cancer treatment, but impairs postoperative bowel function, leading to low anterior resection syndrome (LARS). Neoadjuvant chemotherapy alone might avoid the negative effect of radiotherapy on bowel function. This study aims to assess the impact of neoadjuvant chemotherapy on LARS and the development of LARS over the first 6 months after surgery. METHODS: Rectal cancer patients were prospectively recruited during June 30, 2018 and December 24, 2019. Bowel function was assessed by the LARS score, which was taken at 1 month, 3 months, and 6 months after surgery via phone call interview. Patients were divided into two groups based on whether they received neoadjuvant chemotherapy (group A) or not (group B). RESULTS: A total of 97 patients were included in the analysis. There was no significant difference between the LARS scores at 1 month, 3 months, and 6 months of both groups. The LARS score at 6 months showed a significant decrease from that of 1 month and 3 months in group B (P < 0.05, P < 0.01) and in all patients (P < 0.05, P = 0.001), and significant difference was found between the LARS scores in group A at the three timepoints (P < 0.05). No significant difference was found between the scores at 1 month and 3 months in both groups and in all patients. CONCLUSION: Neoadjuvant chemotherapy alone did not have a negative impact on LARS. The bowel function after surgery started to show significant improvement at 6 months after surgery.

Wavefunction engineering for efficient photoinduced-electron transfer in CuInS2 quantum dot-sensitized solar cells.

The high efficiency of quantum dot-sensitized solar cells (QDSSCs) is a benefit of the highly efficient photoinduced-electron transfer (PET) to external electrodes. Here, we investigated how the surface defects and conduction-band (CB) offsets between core and shell materials affect the PET from CuInS2 quantum dots (QDs) by means of time-resolved femtosecond transient absorption and nanosecond photoluminescence spectroscopy. The transfer of 1S excited electrons from CuInS2 QDs to TiO2 films is demonstrated and we find that the surface-electron trapping can significantly reduce the efficiency of the PET. Though the electron trapping can be suppressed after ZnS surface passivation, the PET decreases significantly to a low efficiency of ∼33% from the type I CuInS2/ZnS core/shell QDs because of their low electron density at the surface of the QDs. The surface-electron density is increased with the strategy of wavefunction engineering by reducing the CB offset, which allows us to achieve a quasi-type II carrier confinement in CuInS2/CdS core/shell QDs. The PET efficiency appears to be as high as ∼95% from the CuInS2/CdS core/shell QDs, which is ascribed to synergistic effects of the surface passivation and enhanced delocalization of the electron wavefunction from the CuInS2 core to the CdS shell. Finally, we demonstrate that these new mechanistic understandings of the PET processes are crucial to improving the efficiency of CuInS2 QDSSCs.

PbS Quantum Dots Sensitized TiO2 Solar Cells Prepared by Successive Ionic Layer Absorption and Reaction with Different Adsorption Layers.

Lead sulfide (PbS) quantum dots (QDs) have been synthesized via successive ionic layer adsorption and reaction (SILAR) on a titanium dioxide (TiO2) nanoporous film for the fabrication of quantum dot-sensitized solar cells (QDSCs). The reaction is environmental friendly and energy saving. The green synthesized PbS QDs match the maximum remittance region of the solar spectrum and are suitable as sensitizers for TiO2 electrodes for cell devices application. PbS QDs were adsorbed in different adsorption layers in order to improve the solar cell performance. The optical properties of PbS sensitized TiO2 films were studied by scanning electron microscopy and UV-Vis absorbance spectroscopy. The photovoltaic characteristics of the PbS QDSCs were analyzed by I-V characteristics and electrochemical impedance spectroscopy. As a result, the light harvesting was enhanced with increasing SILAR adsorption layers. The maximum photovoltaic conversion efficiency of the PbS QDSCs (3.14%) was obtained at the 12 adsorption layers with the highest short circuit current density and lowest charge transfer resistance.

Charge and Energy Transfer Between CdSe Quantum Dots and Polyaniline.

CdSe quantum dots (QDs) and polyaniline (PAni) were mixed to prepare CdSe QDs/PAni complex. PAni can quench the fluorescence of CdSe QDs. Fluorescence intensity of CdSe QDs/PAni complex is related to the size of CdSe QDs and the concentration of PAni. UV-Vis absorption spectra, fluorescence spectra, time-resolved fluorescence spectroscopy were used to analys the quenching phenomenon. The mechanism of fluorescence quenching is dependent on two factors: on one hand, the Förster resonance energy transfer from CdSe to PAni; on the other hand, PAni can intercept the charge relaxation process of CdSe and lead to the interruption of radiative recombination.

Controlling the fluorescent properties of aqueous CdTe nanocrystals by modulating the growth rate.

Although high quality aqueous CdTe and CdTeS alloyed quantum dots (QDs) have been synthesized in recent years, the relationship between the fluorescent properties and the growth kinetics has not been well documented yet. In this paper, 3-mercaptopropionic acid stabilized aqueous CdTe nanocrystals (NCs) are generally prepared with an improvement of the "traditional" synthetic approach, where the preparation of the red emission NCs is usually time-consuming due to the slow growth rate. The investigation on the kinetic and thermodynamic growth process shows that the growth can be effectively accelerated by decreasing the ligand concentration from 0.06 to 0.01 mol/L or elevating the growth temperature from 120 to 240 degrees C. In contrast to previous results, the quantum yield (QY) of the CdTe NCs is heightened to 45% only by increasing properly the growth rate. Our experiments depict that high growth rate favours high concentration of free monomers and thus decreases the number of the surface Te atoms of the NCs, leading to the enhancement of the photoluminescence (PL) QY.

Energy transfer from CdSe quantum dots to porphyrin via two-photon excitation.

CdSe quantum dots have been used as energy donors to activate meso-tetra (4-sulfonatophenyl) porphine dihydrochloride. Pulses of 130 fs duration at a wavelength of 800 nm are used as the two-photon excitation light source. After excitation, steady-state and time-resolved fluorescence spectra are collected for samples with different ratio between the amount of porphyrins and quantum dots. Decay kinetic curves of CdSe quantum dots with and without porphyrins are well fitted by the biexponential decay curve, which indicates a combination of two components (excitonic and trapping state) in the luminescence behavior of CdSe quantum dots. Relative intensity weights of the excitonic and trapping state, total and nonradiative energy transfer efficiency, average luminescence lifetimes of donors are calculated. The nonradiative transfer mechanism becomes the leading factor as the concentration of acceptors gets higher. It is considered to take place through the channel of trapping states of CdSe quantum dots, which is expressed by the weight change between the fast and slow luminescence components. This deduction presents a new way of raising the energy transfer efficiency by increasing the trapping state proportion of the quantum dots, which can be easily realized by surface modification.