Emission-wavelength-dependent photoluminescence decay lifetime of N-functionalized graphene quantum dot downconverters: Impact on conversion efficiency of Cu(In, Ga)Se2 solar cells

Alkaline n-gqds fluorescent probe for the ultrasensitive detection of creatinine

Creatinine (Crn) is an important excretory product of the human body. Medical laboratory technology has improved over years and brought many advancements in clinical diagnostics equipment, and testing techniques and made the tests more efficient. Yet, the quantitative analysis of Crn is still carried out by the classical Jaffe's reaction (using Picric acid (PA) with NaOH) method. Since PA is hazardous to human health, alternative solutions such as; nanoparticles and surface-modified nanoparticles can be used. Exploring the optoelectronic properties of carbon-based quantum dots for biomolecule sensing is of current interest among researchers. Nitrogen functionalized graphene quantum dots (Alk-NGQDs) measured featured Crn easier and reduced the time taken for the test carried out in laboratories. The synthesized Alk-NGQDs optical, structural, morphological properties, surface and compositions are studied through XPS, HRTEM, XRD, FTIR, and spectroscopic techniques. Alk-NGQDs at alkaline conditions (pH 9.5) form a stable complex with Crn through intermolecular charge transfer (ICT). The fluorescence titration method is used to sense Crn in commercial Crn samples and human blood serum. To understand the efficacy of sensing creatinine using Alk-NGQDs, working concentration, fluorescence quantum yield, the limit of detection, and quenching constant are calculated using the Stern-Volmer plot. The emission property of Alk-NGQDs is aimed to bring an alternative to the traditional colorimetric Jaffe's reaction.

Recent advances in the modification of carbon-based quantum dots for biomedical applications

Carbon-based quantum dots (CDs) are mainly divided into two sub-groups; carbon quantum dots (CQDs) and graphene quantum dots (GQDs), which exhibit outstanding photoluminescence (PL) properties, low toxicity, superior biocompatibility and facile functionalization. Regarding these features, they have been promising candidates for biomedical science and engineering applications. In this work, we reviewed the efforts made to modify these zero-dimensional nano-materials to obtain the best properties for bio-imaging, drug and gene delivery, cancer therapy, and bio-sensor applications. Five main surface modification techniques with outstanding results are investigated, including doping, surface functionalization, polymer capping, nano-composite and core-shell structures, and the drawbacks and challenges in each of these methods are discussed.

Fully stoichiometric Cu2BaSn(S1-x Se x )4 solar cells via chemical solution deposition

Cu₂BaSn(S_1-x Se _x )₄ has shown great prospects in the photoelectric field due to Earth-abundance, low toxicity, cost efficiency, direct bandgap, high absorption coefficient (>10⁴ cm^-1) and reduced anti-site disorder relative to Cu₂ZnSn(S_1-x Se _x )₄. A fully-tunable ratio of S/Se is the key to broaden the bandgap of Cu₂BaSn(S_1-x Se _x )₄. Here, we introduce a thionothiolic acid metathesis process to readily tune the stoichiometry of Cu₂BaSn(S_1-x Se _x )₄ films for the first time. Different stoichiometric Se/(S + Se) of Cu₂BaSn(S_1-x Se _x )₄ from zero to one can vary the bandgap range from 2 to 1.68 eV. The grain size of Cu₂BaSn(S_1-x Se _x )₄ films can be grown more than 10 μm. The optimized bandgap and high-quality growth of Cu₂BaSn(S_1-x Se _x )₄ films ensure the best power conversion efficiency of 2.01% for solution-processed Cu₂BaSn(S_1-x Se _x )₄ solar cells. This method provides an alternative solution-processed way for the synthesis of fully stoichiometric Cu₂BaSn(S_1-x Se _x )₄.

Bimetallic Implanted Plasmonic Photoanodes for TiO2 Sensitized Third Generation Solar Cells

An auspicious way to enhance the power conversion efficiency (PCE) of third generation sensitized solar cells is to improve the light harvesting ability of TiO2 sensitizer and inhibition of back recombination reactions. In the present work, we have simultaneously comprehended both the factors using stable bimetallic Au and Ag metal nanoparticles (Mnps) embedded in TiO2 with ion implantation technique at lower fluence range; and explored them in third generation dye sensitized solar cells (DSSCs). The best performing Au-Ag implanted DSSC (Fluence- 6 × 1015 ions cm-2) revealed 87.97% enhancement in its PCE relative to unimplanted DSSC; due to plasmon induced optical and electrical effects of Mnps. Here, optimized bimetallic Au-Ag Mnps embedded in TiO2 improves light harvesting of N719 dye; due to the well matched localized surface plasmon resonance (LSPR) absorption band of Au and Ag with low and high energy absorption bands of N719 dye molecules, respectively. Furthermore, Au and Ag acts as charge separation centers in TiO2 that inhibit the recombination reactions occurring at photoanode/electrolyte interface via prolonging photo-generated electron lifetime; resulting in efficient inter-facial charge transportation in DSSCs.

Visual monitoring of trace water in organic solvents based on ecofriendly b/r-CDs ratiometric fluorescence test paper

Developing a green, non-toxic and easy to synthesize of fluorescence probe for fast and visual detecting trace water in various organic solvents was an important task. Here, a novel dual-emission fluorescence probe (b/r-CDs) was designed based on the red CDs (r-CDs) and blue CDs (b-CDs) to detect the trace water and enhance the visualization for naked-eye observation in different organic solvents. Among, the red fluorescence carbon dots (CDs) was found to have the capability to monitor trace amounts of water, which synthesized with green tea by facile ultrasonic method. Further, Such a dual-emission probe could fast monitor trace water in various organic solvents with high stability and fast response. Importantly, a synergistic mechanism of the dynamic process (b-CDs) and static quenching (r-CDs) was proved for the study of water detection. Moreover, the test paper was made for detecting trace water in different organic solvents, achieving convenient and effective detection.