Emerging Trends in Chemical Sciences

Type 2 diabetes (T2D) is a chronic disease characterised by a combination of insufficient insulin release and an excess of glucagon secretion. The gut hormone glucagon-like peptide-1 (GLP-1) is a successful therapy for the treatment of diabetes as it can both potentiate glucose-induced insulin secretion as well as inhibit glucagon secretion from the pancreatic alpha cells. Another major gut hormone called peptide tyrosine tyrosine (PYY) has recently been reported to restore impaired insulin and glucagon secretion in islets from severely diabetic rats and humans. Whilst the mechanism by which both PYY and GLP-1 normalise insulin secretion is well characterised, to date the regulation of glucagon release by the two gut hormones remains unclear. Given that the GLP-1 receptor is expressed at extremely low levels on alpha-cells, it has been argued that the effects of GLP-1 may be mediated by paracrine (indirect) mechanisms. In contrast, there is also evidence that GLP-1 directly regulates glucagon secretion in isolated alpha-cells, excluding the possibility of islet cross-talk. Likewise, no receptors for PYY have been demonstrated in the alpha-cells that can explain the robust effects of the hormone on glucagon release. Elucidation of the mechanism of GLP-1 (and PYY) action on alpha cells necessitates further work. Specifically it will be important to determine if GLP-1 can mediate its effects via another receptor on alpha-cells.

Capabilities of the radio frequency glow discharge optical emission spectroscopy (RF-GD-OES) for analysis of Ta₂O₅/Nb₂O₅ and tantalum and niobium in electrically non-conducting geological samples were investigated. The metal pentoxides (Ta₂O₅ and Nb₂O₅) and the tantalite mineral powders were mixed with a thermally conductive copper powder in ratios of up to 1:10 sample:copper and pressed into a disc sample for glow discharge sputtering. Studies were carried out to determine and optimize all the parameters affecting the analyses by the RF-GD-OES technique. This included the determination of the ability of the methodology to generate usable analytical curves for the target elements. Good calibration curves which were used for analyses of Ta and Nb in the tantalite minerals were obtained at optimized experimental conditions. Respective tantalum and niobium recoveries were in the order of 99.78–104.91% and 98.34–102.03% from the mineral analyses.

The purpose of this study was to determine the chemical composition of essential oils from Tagetes minuta from the Eastern Cape of South Africa and evaluate their antioxidant potential for medicinal end use. The essential oils were extracted by hydrodistillation method from fresh and dry parts (stem, leaves and flowers) of Tagetes minuta collected from Komga, Eastern Cape Province, South Africa and analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and gas chromatography (GC). This analysis has led to the identification of 12, 31, 10, 37, 4 and 39 compounds representing 99.16, 98.07, 98.86, 98.30, 100 and 97.66% of fresh stem (TMFS), dry stem (TMDS), fresh leaves (TMFL), dry leaves (TMDL), fresh flower (TMFF) and dry flower (TMDF) essential oil respectively. The major components were identified to be cis-β-ocimene (38.03%) for TMFS; caryophyllene oxide (18.04%) for TMDS; trans, cis-alloocimene (25.35%) for TMFL; isopropyl tetradecanoate (17.02%) for TMDL; cis-β-ocimene (38.14%), for TMFF and trans-β-ocimene (37.03%), for TMDF. The dry parts (TMDS, TMDL and TMDF) essential oil were evaluated for antioxidant activity using DPPH and FRAP bioassays. Standard equivalent values from DPPH assay were between 6.74 ± 0.27 and 18.7 ± 0.35 μg/mL AAE with scavenging ability in descending order: TMDF > TMDL > TMDS. Standard equivalent values from FRAP assay were between 26.30 ± 0.41 and 113.0 ± 1.2 μg/mL AAE with antioxidant activity in descending order: TMDF > TMDL > TMDS. These results suggest that T. minuta may be used as a potential natural source of antioxidant.

Neurodegenerative diseases are a heterogeneous group of disorders. They are characterized by progressive degeneration of the structure and function of the central nervous system or peripheral nervous system. Neurodegenerative diseases include Parkinson’s Disease (PD), Alzheimer’s Disease (AD), Amyotrophic Lateral Sclerosis (ALS) and Huntington’s Disease (HD). Key characteristic feature of neurodegenerative diseases is aggregation of misfolded proteins in the cytoplasm and nucleus of central nervous system (CNS) neurons. In this review we discuss about the emerging therapeutic compounds and targets for treating these devastating neurological disorders. Oxidative stress appears to be a common denominator and transcription factors are also involved. Compounds that can scavenge free radicals showed some potential. Some protein and peptide compounds also exhibited good therapeutic activity. Ligand binding domains are targeted for efficacy and showed promise. Agonists and antagonists of receptors and enzyme inhibitors are playing a remarkable role in controlling the symptoms of these diseases. Chemical chaperones and compounds that can inhibit the protein aggregation are widely tried and showing therapeutic potential.

The fluoride removal ability of industrial waste (fly ash) from ground water was studied at different concentrations, contact times, reaction temperatures, adsorbent dosage, coexisting anions and pH of the solution. The rate constants of adsorption, intraparticle transport, mass transfer coefficients and thermodynamic parameters have been calculated at 303 K, 313 K and 323 K. The empirical model has been tested at various concentrations for the present system. The removal of fluoride is favourable at low concentration (5 ppm), high temperature (313 K) and under highly acidic conditions. The batch adsorption process fitted well the Langmuir isotherm and the adsorption kinetics followed the pseudo-second-order rate equation. The physicochemical properties of fly ash were characterized by X-ray diffraction, Fourier Transform infrared spectroscopy and scanning electron microscopy.

This review compares the efficiency of a three-step procedure developed by the authors for the synthesis of flavanones that relied on the boron trifluoride diethyl etherate (BF₃·OEt₂)-mediated reaction of cinnamic acid and phenols to the one-step or two-step procedures reported in literature involving the reaction of 2-hydroxyacetophenones and benzaldehydes. The three-step procedure was found to give the flavanones in comparable yields to both the one-step and the two-step literature methods.

Surface functionalized biosorbent was developed from mango seed shell powder through ethylenediaminetetraacetic acid (EDTA) grafting and encapsulation in calcium alginate gel beads. Introduction of EDTA to the sorbent surface was established by elemental analysis and Fourier transform infra-red spectroscopic analysis. The performance of the composite biosorbent in the removal of copper, chromium, nickel and iron from electroplating wastewater was evaluated through consecutive batch column adsorption and desorption experiments. At innate initial pH of 3.4, metal removal varied within the following ranges: 5.5–12.3% for copper, 2.3–14.8% for chromium, 2.3–4.4% for nickel, and 2.3–13.8% for iron. Acidification of the wastewater to initial pH of 1.8 yielded generally higher metal removal. This hinted at chromic ester formation followed by a redox reaction involving oxidation of –CH₂OH groups on the cellulosic components of the mango material to more potent –COOH groups simultaneously with reduction of chromium from hexavalent to trivalent state.

Large tracts of soil in sub-Saharan Africa are nutrients deficient while inorganic fertilizers are unaffordable for most subsistence farmers. Rotations and/or intercropping of nitrogen fixing trees like Acacia species with crops may alleviate the nitrogen deficiency through biological nitrogen (N₂) fixation and redistribution of subsoil nitrogen to the surface. The study was conducted on an N-deficient, sandy loam (Alfisol) under bimodal rainfall conditions at Kendu Bay, Nyanza Province in Kenya to compare the effectiveness of A. nilotica, A. senegal and A. xanthophloea. This was carried out in order to improve degraded lands by fixing nitrogen from the air, extracting water and nutrients from the soil and investigating the resulting effects on maize yields. Optimal spacing for the Acacia trees for the nitrogen fixation was also evaluated in two seasons to enhance maize yields and nutrients extractions from the soil. Assessment of the relationship between the amount of phosphorus in the soil and nitrogen fixation/availability by the Acacias were also carried out simultaneously. There was poor response in the first season but there was significant increase (P < 0.05) in maize yield due to planting A. nilotica, A. senegal and A. xanthophloea in the second season. The planting of A. nilotica at different spacing in the second season also contributed to the significant increase in the maize yield. In the first season, the Acacias intercropping reduced maize yields. The yield reduction in the first season might be attributed to competition with maize plants when the trees had not grown long enough roots for effective nodulation, and nitrogen fixation while in the second season the Acacia trees had grown long roots that were effective in the nitrogen fixation. Again in the first season close planting spacing of the Acacia reduced yields of the maize. In the second season there was significant (P < 0.05) maize yield increase under closely spaced Acacia trees. These results demonstrate that the benefits of Acacia intercropping in increasing maize yields are more effective after the Acacias have grown and the close spacing of Acacia may be more beneficial in effective nitrogen fixation and supply in the long run. There was increase in phosphorus concentration in maize plants in season two whereby A. nilotica had an increase in phosphorus from 0.183% in season one to 0.363% in season two. The close spacing of the trees was important in phosphorus build up and nitrogen fixation as shown by higher amounts of nitrogen in the soil and maize plants in season two. Soil pH did not vary and remained almost neutral with soil moisture content increasing due to added organic matter from the trees. The findings of this study can be used to intensify agroforestry at the farm level to increase food security in the Lake Victoria Basin and the work should involve all the stakeholders (farmers, extension officers, researchers, non-governmental organizations, leaders, and community based organizations) in decision making and implementation.

A reliable, simple, rapid and cost-effective extraction method based on ultrasonic-assisted dispersive solid phase microextraction (UA-DSPME) method using silica@multiwalled carbon nanotubes hybrid nanostructures combined with spectrophotometric detection was developed for the first time for preconcentration and determination of aflatoxin B₁ (AFB1) in liquid milk samples. Two level factorial design and central composite design in combination with response surface methodology were used to evaluate the factors affecting extraction and preconcentration procedure. The influence of different variables including mass of adsorbent, extraction time, eluent volume and sample volume was investigated in the optimization study. Under the optimal conditions, a dynamic linear range of 0.3–250 μg L⁻¹ with detection limit of 0.1 μg L⁻¹ was obtained. The intraday and interday precisions expressed as relative standard deviations were 3.2% and 4.3% respectively. The developed UA-DSPME/UV-Vis method was applied for extraction and preconcentration of AFB1 in real milk samples. As a result of relatively high enrichment factor (108), satisfactory extraction recoveries (96.8–99.2%) using only 62 mg of an adsorbent were achieved.

This study examines the uptake mechanism of pine cone for the removal of nickel and cobalt from aqueous solution. Surface characteristics of pine cone powder were analysed by Fourier Transform Infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). To explain the mechanism of adsorption, change in solution pH and adsorption isotherms were applied. Increasing solution pH led to increased Ni(II) and Co(II) uptake with Ni(II) being more adsorbed. Adsorption capacities correlated well with change in solution hydrogen ion concentration when solution pH was varied between 3 and 8 and metal ion concentrations were varied between 5 and 150 mg/dm³. FTIR analysis before and after adsorption showed C=O, C–O and phenolic-OH peaks changed in intensity and shifted in position. Dubinin–Radushkevich isotherm better fitted the experimental data than the Temkin isotherm. The affinities of the metals for functional groups on pine cone depended on ionic radius, surface precipitation complexes and covalent bond strength. The equilibrium binding constants increased with temperature, while heat of biosorption decreased with temperature suggesting biosorbent–biosorbate interaction effect. Desorption studies confirmed the ion-exchange mechanism. It was observed that Ni(II) showed stronger ion-exchange properties than Co(II) biosorption.

A simple, sensitive and selective method based on the combination of micro solid phase extraction and HG-ICP-OES for speciation analysis of Sb, Se and Te in environmental samples, has been developed. Titanium dioxide/multiwalled carbon nanotubes (TiO₂@MWCNTs) nanocomposite functionalized with Aliquat 336 was used as the sorbent material. Optimization of factors affecting the speciation of the target analytes was achieved using fractional factorial and Box-Behnken designs. Under optimum conditions, the limit of detection (n = 25) ranged from 1.0 to 1.6 ng L⁻¹. The repeatability and reproducibility (expressed in terms of relative standard deviation) ranged from 1.2–2.3% and 3.1–4.2%, respectively. The accuracy of the developed method was tested by the analysis of a certified reference material and spiked samples and the recovery percentages ranged from 96 to 109%. The proposed method was applied for the quantification of Sb, Se and Te species in real samples. The concentrations of total trace metals determined using the developed method were compared with those obtained using ICP-MS and the results obtained were in close agreement as statistically confirmed using Student paired t-test.

A new generation of battery technologies is necessary to address the challenges of the increasingly complex energy systems our society requires. A lithium-ion battery (LIB) is an advanced battery technology that uses lithium ions as a key component of its electrochemistry. Manganese oxide cathode material of rechargeable lithium-ion batteries offers a unique blend of lower cost and toxicity compared to the normally used cobalt, and has been demonstrated to be safer on overcharge. The common disadvantages affecting its performance are amendable through morphological and electrochemical properties changes. In this research work, alloy nanoparticles were synthesized and used as coating material with the objective to improve the microstructure and catalytic activities of pristine LiMn₂O₄. Co-precipitation and calcination methods were used to coat the LiMn₂O₄. The pristine LiMn₂O₄ and modified materials were examined using a combination of spectroscopic and microscopic techniques along with in detail galvanostatic charge–discharge tests. Microscopic results revealed that the novel composite cathode materials had high phase purity, well-crystallized particles and consistent morphological structures with narrow size distributions. The LiPtAu_xMn_2−xO₄ cathode effectively accommodated the structural transformations, which occur during Li⁺ ion insertion with exchange current density i ₀ (A cm⁻²) of 1.83 × 10⁻⁴ and 3.18 × 10⁻⁴ for LiMn₂O_4. The enhancement of the capacity retention and higher electrode coulombic efficiency of the LiPtAu_xMn_2−xO₄ were significant, especially at high C rate. At enlarged cycling potential ranges the LiM_xMn_2−xO₄ (x = 0.02) sample delivered relevant discharge capacity of 90 mAh g⁻¹ compared to LiMn₂O₄ (45 mAh g⁻¹).

1,3,4-Oxadiazole bearing compounds are one of the most attractive class for researchers due to their biological activities. In the undertaken research, a new series of 5-substituted 1,3,4-oxadiazole-2-yl-4-(piperidin-1-ylsulfonyl)benzylsulfides (6a–k) were synthesized. The synthesis was carried out by converting different organic acids sequentially into corresponding esters, hydrazides and 5-substituted-1,3,4-oxadiazole-2-thiols (4a–k). Finally, the target compounds, 6a–k were prepared by stirring 5-substituted-1,3,4-oxadiazole-2-thiols with 1-(4-(bromomethyl)phenyl sulfonyl)piperidine (5) in the presence of N,N-dimethylformamide (DMF) and sodium hydride. All the structures were elucidated by modern spectroscopic techniques. The synthesized compounds were screened against butyrylcholinesterase (BChE) enzyme and also subjected for molecular docking studies to find ligand-BChE binding affinity and ligand orientation in active sites of human BChE protein. Amino acid residues such as Gly116, His438, Tyr332 and Ser198 are found to be important common residues for binding of highlighted compounds and are likely to be involved in the ligands’ stabilization in the binding site.

Interest in the Zr and Hf fluoride compounds stemmed from a need for water soluble reference materials (RM) for analytical method development and validation of Zr/Hf containing materials and minerals. Numerous mono-valent inorganic (alkali metals) and organic (ammonium type) cations were used to try and isolate the (Zr/Hf)F₆ ²⁻ anions.

The structures that were isolated for some of these cations indicated the profound influence of the cation on the type and coordination of the metal-fluorido bonds in these compounds. The coordination number of the metal center changed from eight for K⁺ (smallest of alkali metals) to six for Cs⁺ (largest of alkali metals) while the type of metal-fluorido bonds ranged from a combination of mono-, di- and tri-bridged to no bridging at all, depending on the size and type of cations used during the crystallization.

The extraction of niobium and tantalum from two tantalum-niobium ore materials obtained from Mozambique, using a combination of magnetic separation, acid leaching, solvent extraction and ion exchange methods was investigated. One sample consisted mainly of manganotantalite while the other of ferrotantalite. The magnetic separation procedure removed 61.8(2)% Fe₂O₃ and 46.4(4)% TiO₂ from the ferrotantalite and 8.9(3)% Fe₂O₃ and 8.8(7)% TiO₂ from manganotantalite. H₂SO₄ leaching removed 62.3(6)% U₃O₈ and 61.1(3)% ThO₂ from manganotantalite and 73.6(2)% U₃O₈ from ferrotantalite. Ammonium bifluoride dissolution and subsequent H₂SO₄ 5-methyl-2-hexanone (MIAK) extraction proved to be the most efficient procedure for separation and isolation of a high purity tantalum oxide. The optimal conditions for Ta separation were 4.0 M H₂SO₄ aqueous solution and organic:aqueous ratio (O/A) = 1:1. Stripping was accomplished using double distilled water. Recoveries of 100.8(3)% Ta₂O₅ and 0.20(3)% Nb₂O₅ for manganotantalite, and 100.50(9)% Ta₂O₅ and 0.67(6)% Nb₂O₅ for ferrotantalite were obtained in the strip solutions. Nb was isolated from the mineral matrices using Dowex Marathon anion exchange resin. Recoveries of 100.2(4)% and 94.5(4)% Nb₂O₅ for manganotantalite and ferrotantalite samples respectively were obtained in the 6.0 M HCl elution, while the other elements were eluted with 4.0 M HCl. The entire process resulted in a total loss of approximately 13% for both Nb₂O₅ and Ta₂O₅ with approximately 96% purity for both metal oxides. Average recoveries of 97.8(7)% Ta₂O₅ and 1.4(6)% Nb₂O₅ were obtained in the Ta rich product while 0.8(4)% Ta₂O₅ and 94.4(5)% Nb₂O₅ were obtained in the Nb rich product.

Bisphenol A (BPA) has been found to be the most rapidly generated endocrine disrupting compound (EDC) with an annual production of over 10 million tons. This synthetic compound has been used extensively in the production of polycarbonate plastics, epoxy resins and thermal papers. It has been detected at elevated levels in industrial wastewater effluents, natural waters and drinking water. Recent studies have shown that BPA affects the proper functioning of the endocrine system in human beings and animals. Exposure to BPA has been associated with immunotoxic, mutagenic and carcinogenic effects at very low levels (ng/L to μg/L). It has also been proven that BPA increases chances of having diabetes, obesity and cancer. Thus, the removal of BPA from water has become a major concern in water research. Enzymatic degradation of BPA has proven to be an efficient and environmentally friendly approach and the use of laccase modified membranes has been reported in many studies. This article provides an in-depth review on the removal of BPA and other toxic organic micro-contaminants from water by laccase modified membrane systems.

This study reports the synthesis and characterization of a novel bio nanosponge filter for applications in water treatment. Firstly the oxidized multiwalled carbon nanotubes (MWCNTs) were chlorinated using oxalyl chloride and then phosphorylated via an amidation reaction. The phosphorylated carbon nanotube (pMWCNT) obtained was polymerized with β-cyclodextrin (βCD) using hexamethylene diisocyanate (HMDI) as a linker. The resulting polymer (pMWCNT-βCD) was decorated by a sol-gel method with TiO₂ and Ag nanoparticles to obtain a biopolymer nanocomposite, pMWCNT-βCD/TiO₂-Ag. For a better evaluation of the target material, CD polymer and pMWCNT-CD polymer were also synthesized for comparison purposes. Fourier-transform infrared (FTIR) spectroscopy was used to confirm the presence of functional groups on the surface of modified MWCNTs and the polymerization reaction. Laser Raman spectroscopy analysis showed the presence of MWCNT, CD and the anatase crystalline form of TiO₂ in the nanocomposite. Preliminary adsorption studies were also conducted in order to test the capability of the new bio nanosponge filter to remove metal ions pollutants from synthetic wastewater solutions.

The monitoring of environmental pollutants is vital to ensure environmental management is effective and potential negative impacts to the environment and human health are understood and mitigated. The sampling and analysis of environmental matrices is often challenging and costly, which invariably curtails the extent of monitoring performed. Researchers are therefore constantly investigating novel alternatives to existing analytical methods, which may offer advantages in terms of parameters such as: cost, speed, selectivity, sensitivity, portability, and accuracy. Herein we review a number of such novel methods for organic pollutants, which we have developed primarily for application in the monitoring of air pollutants. Semi-volatile organic air pollutants, such as polycyclic aromatic hydrocarbons (PAHs), may be present in both the gas and particle phases. Novel denuders which can simultaneously sample both phases have numerous benefits over traditional sampling approaches, including reduced sampling artifact formation and portability. Biomonitors are a cost effective means of sampling over wide geographical areas. The use of lichens as biomonitors for atmospheric PAHs as well as airborne metals can provide useful environmental monitoring information. In addition, nanomaterials, such as quantum dots, show promise in fluorescence sensor applications for the detection of organic pollutants (including PAHs) in water.

Microbial marine endosymbionts are considered a rich source of secondary metabolites with pharmaceutical, industrial, and agricultural value. This comes after research has shown that the microorganisms harbored by marine invertebrates are likely to be responsible for the production of a significant number of compounds isolated from marine invertebrates. In this study a number of isolated marine bacteria were cultured on different media in order to explore and activate secondary metabolite genes encoded in their genome. The antimicrobial properties were assessed using eight test strains (E. coli 1699 [Cubist Pharmaceuticals], B. cereus ATCC10702, P. putida ATCC27853, M. aurum, S. epidermidis ATCC14990, multi-resistant S. aureus-MRSA-MB5393, A. fumigatus ATCC 46645 and C. albicans MY1055) utilizing well diffusion, agar overlay and high throughput screening (HTS). The strains with interesting antimicrobial profiles were identified by sequencing the 16S rRNA gene. Production of secondary metabolites, activation and deactivation were observed under different laboratory culturing conditions. Several strains showed multiple antimicrobial activity either on solid or liquid media. These results indicate the presence and expression of different secondary metabolite pathways under different media composition and confirm the notion that microorganisms associated with marine sponges are a great source of bioactive secondary metabolites.

Microporous and mesoporous silica catalysts, MCM-41, derived from zeolite type catalysts, are easily synthesized in laboratory scale and commercially available SiO₂ have applications in reduction reactions. Nickel boride (Ni B) silica catalysts denoted as Cat A were characterized by XRD, IR, SEM, BET surface area and chemisorption studies. Nickel boride generated in situ on silica were found to be super active catalysts for reduction of nitro aromatics, aldehydes, ketones, alkenes, phenols and in reductive amination of aldehydes and ketones at low temperatures, whereas Pd(II)-MCM-41 denoted as Cat B exhibited catalytic activity for reduction of nitro aromatics, aldehydes, and hydrodehalogenation reactions. Efficient catalytic activity for reduction reactions was exhibited by the Ni and Pd catalysts which were found to be reusable, atom economy, reproducible and environmentally friendly. A comparative study of these catalysts is presented.

Erythrina abyssinica is one of over 100 species that belongs to the genus Erythrina and that is widely used in traditional medicine. It is used in the treatment of various ailments, one of which is the management and treatment of type 2 diabetes. The increasing prevalence of diabetes worldwide and especially in Africa has become a serious public health concern. The need to develop novel therapies with mechanisms of action that are mimetic of the insulin-signaling pathway is necessary in face of the high rates of secondary failure and side effects of existing therapies. One of these potential targets that has emerged is protein tyrosine phosphate 1B, which recently was identified as a major negative regulator in the insulin-signaling pathway. Cohort studies showed reduced risk of type 2 diabetes associated with high intakes of dietary flavonoids. In this study, we described the isolation and protein tyrosine phosphate inhibitory activity of various flavonoids from Erythrina abyssinica. Sixty-eight flavonoids were identified and 43 were found to inhibit protein tyrosine phosphate 1B in a dose dependent manner, with inhibition values ranging from 4.2 to 40 μM.

2-Amino-5-bromo-3-iodoacetophenone and 2-amino-5-bromo-3-iodobenzamide represent important synthons for the design and synthesis of various nitrogen-containing heterocyclic compounds and their annulated derivatives. We have demonstrated that these halogenated aniline derivatives undergo palladium catalyzed Sonogashira cross-coupling with terminal acetylenes to afford the corresponding 2-amino-3-(arylalkynyl)acetophenones and 2-amino-3-(arylalkynyl)benzamides. These alkynylated aniline derivatives in which the alkynyl moiety is adjacent to the nucleophilic nitrogen atom were, in turn, subjected to palladium chloride-mediated heteroannulation to yield novel 1-(2-aryl-1H-indol-7-yl)ethanones and 2-aryl-1H-indole-7-carboxamides, respectively. Molecular hybridization to append an indole moiety to a chalcone framework was achieved via initial Claisen-Schmidt aldol condensation of 2-amino-5-bromo-3-iodoacetophenone with benzaldehyde derivatives followed by sequential palladium catalyzed Sonogashira cross-coupling and heteroannulation. Likewise, boric acid-mediated cyclocondensation of the 3-alkynyl-5-bromoanthranilamides with benzaldehyde derivatives followed by palladium chloride-mediated cyclization afforded the corresponding 2,3-dihydro-1H-pyrrolo[3,2,1-ij]quinazolin-1-ones.

Though impressive progress on the power conversion efficiency of organic solar cells (OSCs) has been made, their practical use is still hampered due to their inherent poor stability. Under ambient conditions the long term stability of non-encapsulated organic solar cells with conventional device architecture is lower than the technical lifetime of devices with an inverted configuration. The removal of the interface between the ITO (indium tin oxide) layer and the acidic PEDOT:PSS layer along with the substitution of a low work function metal electrode with a high work function metal electrode in the inverted device configuration renders relatively higher stability in these devices. Though encouraging device performance (with respect to both stability and efficiency) is seen in inverted organic solar cells, there exists a few technical challenges in the fabrication of these devices namely (1) processability; (2) light-soaking and (3) stability. In this short review we will focus on tackling the processability issue of the device fabrication. Firstly, an overview of recent developments of inverted organic solar cells (IOSC) using various photoactive layers and charge transport layers will be presented. Secondly, the inferior wettability of the hydrophilic PEDOT:PSS hole transport layer onto the photoactive layer such as the P3HT:PCBM blend, which is hydrophobic in nature will be discussed. Thirdly, we will summarize how this issue was addressed successfully and finally, a brief conclusion and an outlook for solution-processed inverted organic solar cells will be presented.