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Whereas extensive studies have examined the effectiveness of inquiry-based learning in chemistry education, few have tracked undergraduate performance throughout the college chemistry curricula. In this study, we describe an instructional model of conceptual learning and inquiry-based practices (CLIP) and assess students’ transformation of knowledge about precision and accuracy in the laboratory components of Introductory Chemistry, Analytical Chemistry, Instrumental Analysis, and Physical Chemistry. Student performance in written laboratory reports reveals that repetition of concepts and specific feedback from instructors are essential in constructing knowledge about precision and accuracy. We observed a distinct gap between students’ perception of their understanding and their ability to determine precision and accuracy in data sets. This gap decreases as students move from introductory to advanced chemistry laboratories, but loss of student participants throughout the study increases the uncertainty in the significance. In contrast to traditional teaching, enhanced learning was observed in Introductory Chemistry I Laboratories thought CLIP, with the support of concept/skill training, specific feedback, and student-centered activities. This study benefits members of the community who are engaged in supporting students’ mastery of theory with practice.

The COVID-19 outbreak has altered chemistry laboratory instruction and forced us to reconsider the balance between face-to-face and online teaching. Our students preferred face-to-face teaching (sc...

It is both challenging and desirable to have drug sensitizers released at acidic tumor pH for photodynamic therapy in cancer treatment. A pH-responsive carrier was prepared, in which fumed silica-attached 5,10,15,20-tetrakis(4-trimethylammoniophenyl)porphyrin (TTMAPP) was encapsulated into 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) nanocomposite liposomes. The sizes of agglomerates were determined by dynamic light scattering to be 115 nm for silica and 295 nm for silica-TTMAPP-DOPC liposomes. Morphological changes were also found in TEM images, showing liposome formation at pH 8.5 but collapse upon silanol protonation. TTMAPP release is enhanced from 13% at pH 7.5 to 80% at pH 2.3, as determined spectrophotometrically through dialysis membranes. Fluorescence emission of TTMAPP encapsulated in the dry film of liposomes was reduced to half at pH 8.6 when compared to that at pH 5.4, while the production of singlet oxygen was quintupled at pH 5.0 compared to pH 7.6. Upon treatment of human prostate cancer cells with liposomes containing 6.7 μM, 13 μM, 17 μM and 20 μM TTMAPP, the cell viabilities were determined to be 60%, 18%, 20% and 5% at pH 5.4; 58%, 30%, 25% and 10% at pH 6.3; and 90%, 82%, 68% and 35% at pH 7.4, respectively. Light-induced apoptosis in cancerous cells was only observed in the presence of liposomes at pH 6.3 and pH 5.4 but not at pH 7.4, as indicated by chromatin condensation.

Selective dimension enlarging integrated with numbering-up is of great importance for microfluidics. However, its feasibility for photochemical processes remains unclear due to the strict requirements of uniform irradiation. Herein, a novel method for selective dimension enlarging in photochemical production was developed by introducing microbubbles. A membrane dispersion microreactor was employed to generate microbubbles for efficient mixing and uniform absorption of photons. With an increased channel size from 0.6 mm to 4 mm, it allowed a 41-fold increase in productivity while maintaining the microscale effect. The yield of was increased by 44−70 % with 83−86 % less side products, compared with those of the homogeneous and segmented flow systems. In addition, a theoretical method combining CFD simulation was developed to predict the change of mixing time with device scales, which could be used to assess the practicality by selective dimension enlarging for different photochemical microfluidic processes.

In a typical chemistry instrumentation laboratory, students learn analytical techniques through a well-developed procedure. Such an approach, however, does not engage students in a creative endeavor. To foster the intrinsic motivation of students’ desire to learn, improve their confidence in self-directed learning activities and enhance their problem-solving skills, students’ self-designed, research-based analytical chemistry projects have been developed within the course of Advanced Chemical Methods for junior and senior undergraduates at SUNY College at Old Westbury. In addition to a series of manual-based laboratories held on a regular basis, students also do a literature search to formulate their own ideas that are tested using appropriate analytical instruments. By participating in self-designed projects, students independently go through the key components of analytical chemistry with greater engagement: from literature survey, problem identification, experimental design, sample preparation, measure...

Thiopurines were examined for their ability to produce singlet oxygen ((1)O(2)) with UVA light. The target compounds were three thiopurine prodrugs, azathioprine (Aza), 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG), and their S-methylated derivatives of 6-methylmercaptopurine (me6-MP) and 6-methylthioguanine (me6-TG). Our results showed that these thiopurines were efficient (1)O(2) sensitizers under UVA irradiation but rapidly lost their photoactivities for (1)O(2) production over time by a self-sensitized photooxidation of sulfur atoms in the presence of oxygen and UVA light. The initial quantum yields of (1)O(2) production were determined to be in the range of 0.30-0.6 in aqueous solutions. Substitution of a hydrogen atom with a nitroimidazole or methyl group at S decreased the efficacy of photosensitized (1)O(2) production as found for Aza, me6-MP and me6-TG. (1)O(2)-induced formation of 8-oxo-7,8-dihydro-2'-dexyguanosine (8-oxodGuo) was assessed by incubation of 6-methylthiopurine/UVA-treated calf thymus DNA with human repair enzyme 8-oxodGuo DNA glycosylase (hOGG1), followed by apurinic (AP) site determination. Because more 8-oxodGuo was formed in Tris D(2)O than in Tris H(2)O, (1)O(2) is implicated as a key species in the reaction. These findings provided quantitative information on the photosensitization efficacy of thiopurines and to some extent revealed the correlations between photoactivity and phototoxicity.

The yield of hydroxyl radicals has been determined by illumination of TiO 2 layers immersed in air saturated aqueous methanol solutions. This yield is equal to half the measured formaldehyde yield in the pH range 7-13. A detailed mechanism is proposed, accounting for the lack of accumulation of hydrogen peroxide. The effect of changing methanol concentration, pH and light intensity (the latter by three orders of magnitude) is in agreement with a very simple mechanism. In contrast to hydroxyl radicals, which react via hydrogen abstraction, leading to formation of HCHO, there is no sign for reaction of methanol with mobile holes. Thus, the limiting quantum yield observed at high methanol concentration is related to the maximum yield of ○OH ads under air saturated conditions at the given pH and light intensity. The effect of light intensity shows the expected inverted square root dependency. The yield of ○OH ads is nearly constant in the range 7 < pH < 12. This system may be useful for comparative tests of different TiO 2 preparations.

We report the singlet oxygen sensitization properties of a series of bis-cyclometalated Ir(III) complexes (i.e., (bt)2Ir(acac), (bsn)2Ir(acac), and (pq)2Ir(acac); bt = 2-phenylbenzothiazole, bsn = 2-(1-naphthyl)benzothiazole, pq = 2-phenylquinoline, and acac = acetylacetonate). Complexes with acetylacetonate ancillary ligands give singlet oxygen quantum yields near unity (PhiDelta = (0.7-1.0) +/- 0.1), whether exciting the ligand-based state or the lowest energy excited state (MLCT + 3LC). The singlet oxygen quenching rates for these beta-diketonate complexes were found to be small [(5 +/- 2) x 105 to (6 +/- 0.2) x 106 M-1 s-1], roughly 3 orders of magnitude slower than the corresponding phosphorescence quenching rate. Similar complexes were prepared with glycine or pyridine tethered to the Ir(III) center (i.e., (bsn)2Ir(gly) and (bt)2Ir(py)Cl; gly = glycine and py = pyridine). The glycine and pyridine derivatives give high singlet oxygen yields (PhiDelta = (0.7-1.0) +/- 0.1).

Singlet oxygen reacts with Ir(I) and Rh(I) thiolato complexes to form the corresponding Ir(III) and Rh(III) peroxo thiolato complexes which do not undergo intramolecular oxidation of the thiolate moiety.

5,10,15,20-Tetrakis(N-(2-(1H-imidazol-4-yl)ethyl)benzamide)porphyrin produced twice as many singlet oxygen ((1)O(2)) molecules at pH 5.0 (quantum yield 0.53 ± 0.01) than at pH 7.4, whereas the (1)O(2) quenching rate was reduced by a factor of 2.5 for a pH change from 7.4 to 5.0.

In this review, we address a highly interdisciplinary field: the use of nanomaterials as carriers for singlet oxygen photosensitizers and their potential applications in photodynamic therapy. In particular, recent advances in the use of nanoparticles including inorganic oxide-, metallic-, and polymer-based nanocomposites as photosensitizer carriers are highlighted. We review advantages and shortcomings of these diverse approaches as far as their application for photodynamic therapy is concerned. Fullerenes and their derivatives are also included, focusing on recent studies on their structure, properties, and ability to generate singlet oxygen.