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1. Quantitative analysis of Δ9-tetrahydrocannabinol (Δ9-THC) in cannabis plants using the Fast Blue BB (FBBB) and 4-aminophenol (4-AP) colorimetric tests

   https://doi.org/10.1016/j.talo.2024.100287  

   Valdes, Nicole B; Gorziza, Roberta; Almirall, José R (August 2024, Talanta Open)

   Banks, Craig (Ed.)

   The Fast Blue BB (FBBB) and 4-aminophenol (4-AP) colorimetric tests have been reportedly used for the qualitative determination of Δ9-THC in plants and for the differentiation between marijuana and hemp-type cannabis. We report the miniaturization of the FBBB colorimetric reaction on a silicone treated filter paper substrate and the analytical figures of merit for a quantitative determination of Δ9-THC for the first time. The reaction between Δ9-THC and FBBB forms a red chromophore that fluoresces when irradiated with visible (480 nm) or UV (365 nm) light, providing a 3-fold increase in sensitivity. Portable instruments are introduced for the objective color determination for both tests and for the fluorescence reading of the THC + FBBB complex. We report a fluorescence signal with Δ9-THC, Δ8-THC, and CBN. The limit of detection (LOD) was determined to be 1.6 ng/μL with precision ~12 % RSD for standard Δ9-THC solutions ranging between 5 and 20 ng/μL. The linear dynamic range for this test is reported between 1.6 ng/μL and 20 ng/μL for the portable fluorescence detector. The miniaturization of both colorimetric tests and the increased sensitivity of the FBBB test using fluorescence analysis, coupled to portable instruments allows for limited quantitative analysis of cannabis plants in the field. 

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2. Selective Anion Sensing in High Salt Water via a Remote Indicator Displacement Assay

   https://doi.org/10.1039/D3CC01974H  

   Hickey, Briana L; Raz, Alexie Andrea; Chen, Junyi; Moreno, Jose L.; Hartman, Joshua D; Zhong, Wenwan; Hooley, Richard James (January 2023, Chemical Communications)

   Water-soluble deep cavitands with cationic functions at the lower rim can selectively bind iodide anions in purely aqueous solution. By pairing this lower rim recognition with an indicator dye that is bound in the host cavity, optical sensing of anions is possible. The selectivity for iodide is high enough that micromolar concentrations of iodide can be detected in the presence of molar chloride. Iodide binding at the “remote” lower rim causes a conformational change in the host, displacing the bound dye from the cavity and effecting a fluorescence response. The sensing is sensitive, selective, and works in complex environments, so will be important for optical anion detection in biorelevant media. 

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3. Functionalized Cellulose‐Co(II)‐Bis‐Terpyridine Hybrid Material as Colorimetric Sensor for Micromolar Aqueous Cyanide

   https://doi.org/10.1002/admt.201800406  

   Collins, Cameron C.; Regalado‐Love, Sean; Portillo, Romeo I.; Boston, David J.; Shores, Matthew P.; Bhowmick, Indrani (October 2018, Advanced Materials Technologies)

   Abstract A novel surface modification approach is taken to cyanide‐sensing by using functionalized cellulose surface that is chemically modified by immobilizing cobalt(II)‐bis‐terpyridine complex on it. The cobalt(II)‐bis‐tpy complex can exhibit selective “naked eye” colorimetric detection of micromolar level cyanide in aqueous solution, where the visible red‐orange color of cobalt(II)‐bis‐tpy complex solution (aqueous) disappears in the presence of cyanide ions. In order to make the sensor more proficient and easy to use, these cobalt(II)‐bis‐tpy molecules are chemically grafted on the surface of microcrystalline cellulose and cellulose paper, which turns the color of functionalized cellulose orange‐red. Both of these colored cellulose powder and paper exhibit color loss in 10⁻⁶maqueous solution of potassium cyanide. This functionalized hybrid inorganic–organic paper offers an easy “dip and detect” cyanide sensing. 

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4. Chemoselective and enantioselective fluorescent identification of specific amino acid enantiomers

   https://doi.org/10.1039/D2CC02363F  

   Pu, Lin (July 2022, Chemical Communications)

   The enantiomers of chiral amino acids play versatile roles in biological systems including humans. They are also very useful in the asymmetric synthesis of diverse chiral organic compounds. Therefore, identifying a specific amino acid and distinguishing it from its enantiomer are of great importance. Although significant progress has been made in the development of fluorescent probes for amino acids, most of them are not capable of conducting simultaneous chemoselective and enantioselective detection of a specific amino acid enantiomer. In this article, several fluorescent probes have been designed and synthesized for chemoselective as well as enantioselective recognition of certain amino acid enantiomers. ( S )-1 shows greatly enhanced fluorescence in the presence of l -glutamic acid and l -aspartic acid, but produces no or little fluorescence response toward their opposite enantiomers and other amino acids. ( R )-4 in combination with Zn 2+ shows greatly enhanced fluorescence in the presence of l -serine. ( S )-6 is designed for the selective recognition of histidine. Micelles made of an amphiphilic diblock copolymer are used to encapsulate the water-insoluble compound ( S )-8 which shows chemoselective as well as enantioselective fluorescence enhancement with l -lysine in the presence of Zn 2+ in aqueous solution. The same micelles are also used to encapsulate several ( S )-1,1′-binaphthyl-based monoaldehydes ( S )-10 for the chemoselective and enantioselective fluorescence recognition of l -tryptophan in the presence of Zn 2+ in aqueous solution. These findings have demonstrated that highly selective fluorescence identification of a specific amino acid enantiomer can be achieved by incorporating certain functional groups at the designated locations of the 1,1′-binaphthyls. The binaphthyl core structure of these probes provides both a chirality source and highly tunable fluorescence properties. Matching the structure and chirality of these probes with those of the specific amino acid enantiomers can generate structurally rigid reaction products and give rise to greatly enhanced fluorescence. The strategies of this work can be further expanded to develop fluorescent probes for the specific identification of many amino acids of interest. This should facilitate the analysis of chiral amino acids in various applications. The outlook of this research and its comparison with other methods are also discussed. 

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5. Receptor Induced Doping of Conjugated Polymer Transistors: A Strategy for Selective and Ultrasensitive Phosphate Detection in Complex Aqueous Environments

   https://doi.org/10.1002/aelm.202101353  

   Benasco, Anthony R.; Tropp, Joshua; Kaphle, Vikash; Chen, Yusheng; Zhao, Wei; Eedugurala, Naresh; Ng, Tse Nga; Flood, Amar H.; Azoulay, Jason D. (March 2022, Advanced Electronic Materials)

   Abstract Phosphate oxyanions play central roles in biological, agricultural, industrial, and ecological processes. Their high hydration energies and dynamic properties present a number of critical challenges limiting the development of sensing technologies that are cost‐effective, selective, sensitive, field‐deployable, and which operate in real‐time within complex aqueous environments. Here, a strategy that enables the fabrication of an electrolyte‐gated organic field‐effect transistor (EGOFET) is demonstrated, which overcomes these challenges and enables sensitive phosphate quantification in challenging aqueous environments such as seawater. The device channel comprises a composite layer incorporating a diketopyrrolopyrrole‐based semiconducting polymer and a π‐conjugated penta‐t‐butylpentacyanopentabenzo[25]annulene “cyanostar” receptor capable of oxyanion recognition and embodies a new concept, where the receptor synergistically enhances the stability and transport characteristics via doping. Upon exposure of the device to phosphate, a current reduction is observed, consistent with dedoping upon analyte binding. Sensing studies demonstrate ultrasensitive and selective phosphate detection within remarkably low limits of detection of 178 × 10⁻¹²m(17.3 parts per trillion) in buffered samples and stable operation in seawater. This receptor‐based doping strategy, in conjunction with the versatility of EGOFETs for miniaturization and monolithic integration, enables manifold opportunities in diagnostics, healthcare, and environmental monitoring. 

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