Highly Sensitive Fluorescent Sensing for Nitrobenzene of CdII Complexes Based on Three Isomers and a Bis-Imidazole Ligand.

Detection of nitro pollutants is an important topic in environmental protection. A total of 3 Cd (II) complexes (1-3) based on 3 soft organic isomers, n-(3,5-dicarboxylato benzyloxy) benzoic acid (n = 2, 3 or 4-H3DBB), and a linear N-donor ligand, 3-bis(imidazole-l-ylmethyl) benzene (3-bibz), have been synthesized hydrothermally. Structural diversity of Complexes 1-3 displays the architectural 2D or 3D change: Complex 1 exhibits a 2D network featuring tri-nuclear metal units, Complex 2 is a 3D framework based on similar tri-nuclear metal units, and Complex 3 shows a 3D network with binuclear units. Fluorescent sensing properties exhibited in all these complexes have been discovered to detect nitrobenzene (NB) selectively and sensitively. In particular, Complex 3 possesses high sensitivity for NB with the lowest detection limit of 1.15 × 10-10 M. The results of the theoretical calculation verified the fluorescence detection mechanism of NB by these Cd-based complexes. Therefore, these Cd-based complexes might be used as excellent luminescent sensors for NB.

Cooperative multiple interactions of donor-π-acceptor dyes enhance the efficiency and stability of perovskite solar cells.

Surface passivation by organic dyes has been an effective strategy for simultaneous enhancement of the efficiency and stability of perovskite solar cells. However, lack of in-depth understanding of how subtle structural changes in dyes leads to distinctly different passivation effects is a challenge for screening effective passivation molecules (PMs). In an experiment done by Han et al. (Adv. Energy Mater., 2019, 9, 1803766), three donor-π-acceptor (D-π-A) dyes (SP1, SP2, and SP3) with distinct electron donors have been applied to passivate the perovskite surface, where the efficiency and stability of PSCs are quite different. Herein, we carried out first-principles calculations and ab initio molecular dynamics (AIMD) simulations on the structures and electronic properties of SP1, SP2, SP3, and their passivated perovskite surfaces. Our results showed that SP3 enhances the carrier transfer rate, electric field, and absorption region compared to SP1 and SP2. Moreover, AIMD simulations reveal that the cooperative multiple interactions of O-Pb, S-Pb, and H-I between SP3 and the perovskite surface result in a stronger passivation effect in a humid environment than that of SP1 and SP2. This work is expected to pave the way for screening dye passivation molecules to endow perovskite solar cells with high efficiency and stability.

The high fluorescence sensitivity property and quenching mechanism of one-dimensional Cd-HCIA-1 sensor for nitrobenzene.

The sensing of nitroaromatic compounds in aqueous solution is closely related to environmental sustainability and human health. In this study, a novel Cd(II) coordination polymer (Cd-HCIA-1) was designed and prepared, and its crystal structure, luminescence performance, detection of nitro pollutants in water, and fluorescence quenching mechanisms were studied. Cd-HCIA-1 exhibited a one-dimensional ladder-like chain based on a T-shape ligand of 5-((4-carboxybenzyl) oxy) isophthalic acid (5-H3CIA). The H-bonds and π-π stacking interactions were then used to construct the supramolecular skeleton in common. Luminescence studies revealed that Cd-HCIA-1 can detect nitrobenzene (NB) in aqueous solution with high sensitivity and selectivity, and the limit of detection was 3.03 × 10-9 mol L-1. The fluorescence quenching mechanism of the photo-induced electron transfer for NB by Cd-HCIA-1 was obtained through an investigation of the pore structure, density of states, excitation energy, orbital interactions, hole-electron analysis, charge transfer, and electron transfer spectra by using density functional theory (DFT) and time-dependent DFT methods. NB was absorbed in the pore, π-π stacking increased the orbital overlap, and the LUMO was mainly composed of NB fragments. The charge transfer between ligands was blocked, resulting in fluorescence quenching. This study on fluorescence quenching mechanisms can be used to develop efficient explosive sensors.

Electrophilicity and Nucleophilicity of Boryl Radicals.

We carried out a survey of the relative reactivity of a collection of 91 neutral boryl radicals using density functional calculations. Their reactivities were characterized by four indices, i.e., the global electrophilicity, global nucleophilicity, local electrophilicity, and local nucleophilicity. Particularly, the global electrophilicity and nucleophilicity indices span over a moderately wider range than those of carbon radicals, indicating their potentially broader reactivity. Thus, boryl radicals may be utilized in electrophilic radical reactions, while traditionally they are only considered for nucleophilic radical reactions. In contrast, the local electrophilicity and nucleophilicity indices at the boron center show a different reactivity picture than their global counterparts. The inconsistency is rooted in the low and varying spin density on boron (for most radicals, less than 50%) in different boryl radicals, which is a combinative result of radical stabilization via electron delocalization and the low electronegativity of boron (compared to carbon). In short, the boron character in boryl radicals may be weak and their reactivity is not reflected by the local indices based on boron but by the global ones.

Fluorescence-quenching mechanisms of novel isomorphic Zn/Cd coordination polymers for selective nitrobenzene detection.

Nitroaromatic compounds in aqueous undermine environmental sustainability and affect human health. The development of a fluorescent sensor capable of efficiently and selectively detecting trace amounts of nitroaromatic compounds presents a considerable challenge. This study introduced Zn/Cd isomeric coordination polymers (Zn-H2CIA-1/Cd-H2CIA-2), which are synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid (5-H3CIA) and 1,10-phenanthroline (Phen). The polymers have zero-dimensional discrete crystal structure with a six-coordinated scissor-like shape. The two coordination polymers can be used as fluorescent sensors for detecting nitrobenzene (NB) and demonstrated favorable sensitivity, with detection limits of 1.95 × 10-8 and 4.66 × 10-7 mol/L, respectively. Zn-H2CIA-1 exhibited stronger fluorescence and a more sensitive response to NB compared with Cd-H2CIA-2. To elucidate their fluorescence-quenching mechanisms, we analyzed Zn-H2CIA-1 by performing DFT and TD-DFT calculations. The pore structure, density of states, excitation energy, hole-electron distribution, and orbital composition were analyzed. The suitable size of pores in Zn-H2CIA-1 is the main reason for its high NB selectivity. Moreover, intermolecular π-π stacking interactions result in an orbital overlap between Zn-H2CIA-1 and NB, enabling the transfer of electrons from Zn-H2CIA-1 to NB. This electron transfer is identified as the fundamental cause of fluorescence quenching in Zn-H2CIA-1.

Quenching and enhancement mechanisms of a novel Cd-based coordination polymer as a multiresponsive fluorescent sensor for nitrobenzene and aniline.

BACKGROUND: Nitroaromatic compounds are inherently hazardous and explosive, so convenient and rapid detection strategies are needed for the sake of human health and the environment. There is an urgent demand for chemical sensing materials that offer high sensitivity, operational simplicity, and recognizability to effectively monitor nitroaromatic residues in industrial wastewater. Despite its importance, the mechanisms underlying fluorescence quenching or enhancement in fluorescent sensing materials have not been extensively researched. The design and synthesis of multiresponsive fluorescent sensing materials have been a great challenge until now. RESULTS: In this study, a one-dimensional Cd-based fluorescent porous coordination polymer (Cd-CIP-1) was synthesized using 5-(4-cyanobenzyl)isophthalic acid (5-H2CIP) and 4,4'-bis(1-imidazolyl)biphenyl (4,4'-bimp) and used for the selective detection of nitrobenzene in aqueous solution by fluorescence quenching, with a limit of detection of 1.38 × 10-8 mol L-1. The presence of aniline in the Cd-CIP-1 solution leads to the enhancement of fluorescence property. Density functional theory and time-dependent density functional theory calculations were carried out to elucidate the mechanisms of the fluorescence changes. This study revealed that the specific pore size of Cd-CIP-1 facilitates analyte screening and enhances host-guest electron coupling. Furthermore, π-π interactions and hydrogen bond between Cd-CIP-1 and the analytes result in intermolecular orbital overlap and thereby boosting electron transfer efficiency. The different electron flow directions in NB@Cd-CIP-1 and ANI@Cd-CIP-1 lead to fluorescence quenching and enhancement. SIGNIFICANCE AND NOVELTY: The multiresponsive coordination polymer (Cd-CIP-1) can selectively detect nitrobenzene and recognize aniline in aqueous solutions. The mechanism of fluorescence quenching and enhancement has been thoroughly elucidated through a combination of density functional theory and experimental approaches. This study presents a promising strategy for the practical implementation of a multiresponsive fluorescent chemical sensor.

Design and preparation of a multi-responsive Cd-based fluorescent coordination polymer for smart sensing of nitrobenzene and ornidazole.

The improper utilization of nitrobenzene (NB) and ornidazole (ORN) has resulted in irreversible effects on the environment. By combining experimental investigation, density functional theory (DFT) calculations, and machine learning, an effective green strategy for detecting NB and ORN in aqueous solutions can be developed. In this study, a one-dimensional Cd-based coordination polymer (Cd-HCIA-3) was designed and synthesized using 5-((4-carboxybenzyl)oxy)isophthalic acid and rigid 2,2'-bipyridine under solvothermal reaction conditions. Cd-HCIA-3 exhibits excellent fluorescence properties and stability in aqueous solutions. DFT calculations were performed to predict the fluorescence sensing performance of Cd-HCIA-3, revealing that photoinduced electron transfer is the key mechanism for inducing fluorescence quenching in the presence of NB and ORN, with weak molecular interactions promoting electron transfer. Fluorescence sensing experiments were conducted to verify the DFT results, showing that Cd-HCIA-3 can selectively detect NB and ORN in aqueous solutions with limits of detection of 7.22 × 10-8 and 1.31 × 10-7 mol/L, respectively. This study's findings provide valuable insights into the design and synthesis of fluorescent coordination polymers for target analytes.

High performance and recyclable Ag/ZnO/PM substrate for the detection of organic pollutants.

A sensitive and recyclable substrate was fabricated through in situ reduction of silver nanoparticles (NPs) on zinc oxide nanorods (NRs). The prepared silver nanoparticles/zinc oxide nanorods/polyamide mesh (Ag/ZnO/PM) substrate exhibited not only excellent surface-enhanced Raman scattering (SERS) performance to R6G with a limit of detection (LOD) of 10-12 M, mainly attributed to the synergistic effect of the suitable size and the nanoscale gaps of the Ag NPs to produce local surface plasmon resonance (LSPR), but also outstanding self-cleaning property via UV irradiation due to its significant photocatalytic property based on the non-equilibrium carriers generated by ZnO and the presence of Schottky junctions between Ag and ZnO. The substrate showed good recycling stability even after five cycles. Furthermore, the successful recyclable application of Ag/ZnO/PM for tetracycline hydrochloride (TC) detection with high sensitivity further suggested that it is a promising candidate for constructing a portable SERS platform to detect organic pollutants.

Highly sensitive detection of nitrobenzene by a series of fluorescent 2D zinc(ii) metal-organic frameworks with a flexible triangular ligand.

Four fluorescent zinc(ii) metal-organic frameworks, namely [Zn(HCIA)(4,4'-bipy)] (1), [Zn2(CIA)(OH)(1,4-bibz)1.5]·H2O (2), [Zn(CIA)(OH) (4,4'-bbpy)] (3), and [Zn2(HCIA) (4,4'-bimp)]·H2O (4), were prepared hydrothermally with a flexible triangular ligand (H3CIA) and a series of linear N-donor ligands (H3CIA = 5-(2-carboxybenzyloxy) isophthalic acid, 4,4'-bipy = 4,4'-bipydine, 1,4-bibz = 1,4-bis(1-imidazoly)benzene; 4,4'-bbpy = 4,4'-bis (imidazolyl) biphenyl; 4,4'-bimp = 4,4'-bis (imidazole-1-ylethyl) biphenyl). Structural analyses revealed that complex 1 exhibited a 2D brick-like network structure based on the basic bimetallic ring, 2 was also a 2D interspersed structure from the 1D tubular structure, compound 3 possessed a 2D (4,4) network with 4,4'-bbpy occupying the holes, and complex 4 displayed a 2D network from the 1D ladder-like chain. The thermal stabilities and fluorescent properties of these complexes were investigated in the solid state. The fluorescent sensing experiments revealed that all Zn-MOFs could highly sensitively detect nitrobenzene in aqueous solution, which indicated that these materials can be used as fluorescent probes for the detection of nitrobenzene.

[Determination of baicalin in Shuanghuanglian oral liquid on composite mercury film electrode based on chemical modified].

OBJECTIVE: A novel Eu-PB composite mercury film electrode (GC/Eu-PB/MFE) based on chemical modified was developed for the determination of baicalin and the investigation of its the electrochemical behavior. METHOD: Cyclic voltammetry and differential pulse voltammetry were used. RESULT: The adsorption characteristic of baicalin was observed in Britton-Robinson buffer solution (pH 6.0) at GC/Eu-PB/MFE. The reduction peak of baicalin was observed at -1.22 V (vs SCE) and peak current was linear to the baicalin from 8.0 x 10(-9) to 1.0 x 10(-6) mol x L(-1) (r = 0.9992, n=8). The limit of detection was 1.2 x 10(-9) mol x L(-1) (S/N = 3). The average recovery was 99.83%, with RSD of 2.3% (n=8). The baicalin in Shuanghuanglian oral can be directly determined without pretreatment. CONCLUSION: The GC/Eu-PB/MFE was used to determine baicalin in Shuanghuanglian oral with good repeatability and high sensitivity. The method can be used for the quality control of Chinese traditional medicines containing Scutellaria baicalensis.

A density functional theory study on the electronic and adsorption characteristics of cyclo M9N9 (M = B and Al).

On the basis of experimental and theoretical calculations conducted for cyclo C18, we predicted two novel inorganic cyclo M9N9 (M = B and Al) molecules. Because of the significant difference in electronegativity between M and N atoms, M-N bonds were ionic. Furthermore, the interaction of cyclo M9N9 with cyclopropylpiperazine (CPPP) was investigated. In cyclo M9N9, each M atom could adsorb one CPPP molecule. The CPPP molecules exhibited a preference to remain outside cyclo M9N9 molecules. Depending on the structural characteristics of CPPP molecules, the exciting part is that up to four CPPP molecules could be adsorbed on the exterior surface of cyclo M9N9. We calculated adsorption energies and analyzed the main structural parameters in the process. The research results indicated that adsorption on cyclo Al9N9 was energetically more favorable than that on cyclo B9N9. The cyclo M9N9 have considerable potential in the future. Graphical abstract.

A novel rhodamine-based colorimetric and fluorometric probe for simultaneous detection of multi-metal ions.

Effective and simultaneous detection of multi-metal ions has been achieved by a colorimetric and fluorometric probe (REHBA) synthesized from rhodamine hydrazide and polyhydroxyl aromatic aldehyde. REHBA can serve as a colorimetric detector for Cu2+ and Co2+, and a fluorometric probe for Pb2+. The colorless solution of REHBA changes to pink for Cu2+/Co2+ and shows a remarkable fluorescence for Pb2+. The further differentiation of Cu2+ and Co2+ depends on whether the colorimetric response of REHBA is reversible upon addition of ethylene diamine tetraacetic acid. The response is reversible for Cu2+, while it is not for Co2+. The spirolactam ring-opening in REHBA and the formation of REHBA-metal complexes with binding stoichiometric ratio of 1:1 are responsible for the UV-visible and fluorescence behaviors. REHBA shows excellent selectivity, anti-interference and good sensitivity. The limit of detection of Cu2+, Co2+ and Pb2+ is 0.11 µM, 0.88 µM and 0.73 µM, respectively. In addition, REHBA has been applied to recognize Pb2+ in living cells by fluorescence image and Cu2+, Co2+ and Pb2+ in real water samples, indicating that REHBA is a potential candidate for multi-metal-ions detection.

A FRET-based fluorescent and colorimetric probe for the specific detection of picric acid.

Picric acid (PA) as an environmental pollutant and high explosive, has recently received considerable attention. In this paper, a novel fluorescent and colorimetric chemo-probe (L) for the highly selective and sensitive detection of picric acid has been revealed. The probe was facilely constructed using rhodamine B, ethylenediamine and 4-(9H-carbazol-9-yl)benzoyl chloride. Significant fluorescence changes based on an intramolecular fluorescence resonance energy transfer (FRET) effect followed by a distinct color change from colorless to pink were observed after addition of picric acid to the probe solution. Selectivity measurements revealed that the as-synthesized probe exhibited high selectivity toward PA in the presence or absence of other analytes. The experimental titration results suggested that the as-synthesized probe is an effective tool for detection of PA with a nanomolar scale detection limit (820 nM) and could also serve as a "naked-eye" indicator for PA detection.

Observation of allylic rearrangement in water-rich reaction.

Allylic rearrangement or the migration of a double bond from its original position in the carbon skeleton to an adjacent site was observed when 3,4,5,6-tetrahydrophthalate was hydrolyzed in a basic solution and in the presence of Co(ii) and Mn(ii) under hydrothermal conditions.