Recent Progress on Covalent Organic Frameworks Supporting Metal Nanoparticles as Promising Materials for Nitrophenol Reduction.

With the utilization of nitrophenols in manufacturing various materials and the expansion of industry, nitrophenols have emerged as water pollutants that pose significant risks to both humans and the environment. Therefore, it is imperative to convert nitrophenols into aminophenols, which are less toxic. This conversion process is achieved through the use of noble metal nanoparticles, such as gold, silver, copper, and palladium. The primary challenge with noble metal nanoparticles lies in their accumulation and deactivation, leading to a decrease in catalyst activity. Covalent organic frameworks (COFs) are materials characterized by a crystalline structure, good stability, and high porosity with active sites. These properties make them ideal substrates for noble metal nanoparticles, enhancing catalytic activity. This overview explores various articles that focus on the synthesis of catalysts containing noble metal nanoparticles attached to COFs as substrates to reduce nitrophenols to aminophenols.

Tiny silver bullets: silver nanoparticles are insecticidal to Culicoides sonorensis (Diptera: Ceratopogonidae) biting midge larvae.

Insecticide formulations with safer environmental profiles and limited off-target effects are desirable to manage medical and veterinary pests. Silver nanoparticles are insecticidal against mosquitos, nonbiting midges, and other insects. The biting midge, Culicoides sonorensis Wirth and Jones, is a vector of agriculturally important pathogens in much of the United States, and this study aimed to examine the insecticidal properties of silver nanoparticles in larvae of this species. Mortality of third-instar larvae was assessed daily for 7 days after exposure to concentrations of silver nanoparticles, sorghum polymer particles, and hybrid silver-sorghum polymer particles. Both silver nanoparticles and silver-sorghum polymer particles were insecticidal, but sorghum polymer particles alone did not significantly contribute to larval mortality. Concentrations of 100 mg/liter of silver nanoparticles achieved >50% mortality at day 7, and 200 mg/liter treatments achieved >75% larval mortality within 24 h. The antimicrobial properties of silver nanoparticles were also examined, and culturable bacteria were recovered from larval-rearing media at 200 mg/liter but not at 400 mg/liter of silver nanoparticles. These data suggest that C. sonorensis larval mortality is primarily caused by silver nanoparticle toxicity and not by the reduction of bacteria (i.e., a larval food source). This work describes the first use of silver nanoparticles in C. sonorensis and shows the potential insecticide applications of these nanoparticles against this agricultural pest. The grain-polymer particles also successfully carried insecticidal silver nanoparticles, and their utility in loading diverse compounds could be a novel toxin delivery system for biting midges and similar pests.

Fatal Food: Silver-Coated Grain Particles Display Larvicidal Activity in Culex quinquefasciatus.

Mosquitoes pose a significant risk to millions of people worldwide since they can transmit pathogens. Current methods to control mosquito populations include the use of synthetic pesticides. Nanotechnology may be a solution to develop new mosquito control. However, one barrier to expanding the impact of nanomaterials is the ability to mass-produce the particles. Here, we report a novel hybrid particle synthesis combining micro- and nanoparticles using the coprecipitation technique with the potential for mass production. These particles may have applications as a mosquito larvacide. The particles reported here were designed using a microparticle zein polymer as the core and a nanoparticle silver as the active ingredient. The hybrid NPs reported here targeted a late-stage mosquito larvae and that resulted in a high larval mortality concentration (1.0 ppm, LC90) and suppression of pupal emergence at 0.1 ppm. This research demonstrates the efficacy of a plant-based core with a metal-based AI coating (AgNPs) against larval mosquitoes.

Optical sensing of aqueous nitrate anion by a platinum(II) triimine salt based solid state material.

Selective and quantitative measurement of aqueous nitrate (NO3-) anion is achieved using solid [Pt(Cl-4-tpy)Cl]ClO4 salt (Cl-4-tpy = 4-chloro-2,2':6'2''-terpyridine), and as the salt supported on controlled porous glass. This detection method relies on the color change of the Pt(II) complex from yellow to red and intense luminescence response upon ClO4- exchange with NO3- due to concomitant enhancement of Pt⋯Pt interactions. The spectroscopic response is highly selective for NO3- over a large range of halides and oxoanions.

pH-Mediated Colorimetric and Luminescent Sensing of Aqueous Nitrate Anions by a Platinum(II) Luminophore@Mesoporous Silica Composite.

Increased levels of nitrate (NO3-) in the environment can be detrimental to human health. Herein, we report a robust, cost-effective, and scalable, hybrid material-based colorimetric/luminescent sensor technology for rapid, selective, sensitive, and interference-free in situ NO3- detection. These hybrid materials are based on a square-planar platinum(II) salt [Pt(tpy)Cl]PF6 (tpy = 2,2';6',2″-terpyridine) supported on mesoporous silica. The platinum salt undergoes a vivid change in color and luminescence upon exposure to aqueous NO3- anions at pH ≤ 0 caused by substitution of the PF6- anions by aqueous NO3-. This change in photophysics of the platinum salt is induced by a rearrangement of its crystal lattice that leads to an extended Pt···Pt···Pt interaction, along with a concomitant change in its electronic structure. Furthermore, incorporating the material into mesoporous silica enhances the surface area and increases the detection sensitivity. A NO3- detection limit of 0.05 mM (3.1 ppm) is achieved, which is sufficiently lower than the ambient water quality limit of 0.16 mM (10 ppm) set by the United States Environmental Protection Agency. The colorimetric/luminescence of the hybrid material is highly selective to aqueous NO3- anions in the presence of other interfering anions, suggesting that this material is a promising candidate for the rapid NO3- detection and quantification in practical samples without separation, concentration, or other pretreatment steps.

Harnessing Fe(III)-Carboxylate Photochemistry for Radical-Initiated Polymerization in Hydrogels.

Coordination of Fe(III) to carboxylates in polyuronic acid hydrogels was used to impart photochemical reactivity to polysaccharide-based hydrogels. This photochemical reaction was then used for light-initiated polymerization to create hydrogels with advanced mechanical and conductive properties by capturing the photogenerated radical with a monomer, either acrylamide, methyl methacrylate, or aniline. The photopolymerization of acrylamide using the Fe(III)-polyuronic acid was quantified in solution and the polymerization efficiency was determined under different conditions. Poly(methyl methacrylate) (PMMA)-modified hydrogels were analyzed by the contact angle, optical microscopy, and rheology. This confirmed formation of a stiff, hydrophobic, PMMA layer on polysaccharide hydrogels after light irradiation in methyl methacrylate. Polyaniline-modified hydrogels were characterized by current-voltage sweeps, which showed the formation of conductive polyaniline integrated into the hydrogel after light irradiation in the aniline monomer. This strategy provided a facile approach to create either layered hydrogels with different stiffness and hydrophobicity or hybrid conductive hydrogels using the simple photochemical reaction of blue light irradiation of Fe(III) coordinated to polyuronic acids.

Phase transformation induced mechanochromism in a platinum salt: a tale of two polymorphs.

Red crystals of [Pt(tpy)Cl]NO3·HNO3 show mechanochromic behaviour turning yellow when pressure is applied. The electronic character and spectroscopic signature of the red and yellow polymorphs change as a result of slipping of the molecular stacking planes in the solid state. The slippage alters the PtPt intermolecular distances from a linear stacked motif with <3.5 Å separations in the red polymorph to a less stacked motif of alternating short intradimer and long interdimer interactions in the yellow polymorph.

A digital imaging method for evaluating the kinetics of vapochromic response.

This work describes the novel use of a cell phone camera and the L*a*b method (color space defined by the International Commission on Illumination) to characterize the color change in different vapochromic platinum(II) complexes in order to get quantitative and more reliable data. In this study, we have developed a semi-automatic CCA software that digitally analyzes images (e.g., video frames) collected while a vapochromic material is absorbing vapor and changing its color. The advantages of using this method, compared to reflectance or transmission spectroscopy through a thin film, include its low cost, convenience, portability, ease of sample preparation, the lack of need for specialized equipment, and the possibility of simultaneously collecting data on different samples under identical conditions. The results show that this strategy is effective in producing quantitative information about the kinetics of processes.

Robotic direct reading device with spatial, temporal, and PID sensors for laboratory VOC exposure assessment.

This study evaluated a novel robotic direct reading method that used a real-time location system to measure the spatial-concentration distribution of volatile organic compounds (VOCs) in a chemistry laboratory. The CEMWIP II is a custom-made sensor that measures VOCs, temperature, humidity, and location, sending data wirelessly in real time to a remote location for display and storage. In this study, the CEMWIP II device was mounted on a robotic platform to create a CEMWIP II-mobile platform. The autonomous mobile platform was released from a corner of the room and allowed to travel randomly along an open floor with the goal of characterizing the spatial distribution of VOCs and identifying their sources in the laboratory. The experiment consisted of 12 runs made of permutations of four corner release sites and four beaker locations, with two beakers containing water and two containing the solvent acetone. The autonomous mobile platform was tasked with locating the two beakers of acetone. The sensor had a detection limit of 100 ppb and the confidence of detecting a source within a 1.46 m2 area was p = 0.0005 by ANOVA. The CEMWIP II-mobile platform was able to measure the spatial distribution of VOCs within a laboratory that were associated with open solvent containers.

Analyte-responsive gated hollow mesoporous silica nanoparticles exhibiting inverse functionality and an AND logic response.

A multifunctional nanoparticle with designed selectivity was made using hollow mesoporous silica, ship-in-a-bottle synthesis of a crystalline solid-state detector, and protection of the crystal by acid-responsive nanogates. The system demonstrates the inverse application of the usual trapping of contents by the gate followed by their release. Instead, the gate protects the contents followed by selective exposure. Crystallization of [Pt(tpy)Cl](PF6) (tpy = 2,2':6',2''-terpyridine) inside the cavity of hollow mesoporous silica created the unique core/shell nanoparticle. The crystalline core becomes fluorescent in the presence of perchlorate. By condensing an acid-sensitive gate onto the particle, access to the pores is blocked and the crystal is protected. The new nanomaterial obeys Boolean AND logic; only the presence of both the analyte (ClO4-) and acid results in the optical response.

Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4(-).

Molecular recognition of an aqueous pertechnetate (TcO4(-)) anion is fundamentally challenging partly due to the charge-diffuse nature of this anion, which hampers design of new technologies for its separation and detection. To address this gap, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF6 (tpy = 2,2';6',2″-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO4(-) uptake due to concomitant enhancement of Pt···Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO4(-) among other competing anions. Complementary Raman spectroscopy and microscopy techniques, structural determination, and theoretical methods were employed to elucidate the mechanism of this response at the molecular level.

Between red and yellow: evidence of intermediates in a vapochromic Pt(II) salt.

[Pt(tpy)Cl]ClO4·H2O (1·H2O) changes from red to yellow upon dehydration due to increased Pt···Pt distances. Spectroscopic, diffraction, gravimetric and calorimetric data demonstrate the presence of intermediates during hydration and dehydration which signifies surprising mechanistic complexity in the vapochromic response.