Synthetic Strategies for the Selective Functionalization of Carbon Nanodots Allow Optically Communicating Suprastructures.

The surface of Carbon Nanodots (CNDs) stands as a rich chemical platform, able to regulate the interactions between particles and external species. Performing selective functionalization of these nanoscale entities is of practical importance, however, it still represents a considerable challenge. In this work, we exploited the organic chemistry toolbox to install target functionalities on the CND surface, while monitoring the chemical changes on the material's outer shell through nuclear magnetic resonance spectroscopy. Following this, we investigated the use of click chemistry to covalently connect CNDs of different nature en-route towards covalent suprastructures with unprecedent molecular control. The different photophysical properties of the connected particles allowed their optical communication in the excited state. This work paves the way for the development of selective and addressable CND building blocks which can act as modular nanoscale synthons that mirror the long-established reactivity of molecular organic synthesis.

The Importance of the Purification Step and the Characterization of the Products in the Synthesis of Carbon Nanodots.

In the synthesis of carbon nanodots (CNDs), the critical step of the purification from the starting materials and unwanted side products is faced. In the exciting race toward new and interesting CNDs, this problem is often underestimated, leading to false properties and erroneous reports. In fact, on many occasions, the properties described for novel CNDs derive from impurities not completely eliminated during the purification process. Dialysis, for instance, is not always helpful, especially if the side products are not soluble in water. In this Perspective, the importance of the purification and characterization steps, in order to obtain solid reports and reliable procedures, is emphasized.

Chiral Carbon Nanodots Can Act as Molecular Catalysts in Chemical and Photochemical Reactions.

In this work, a microwave synthesis followed by a simple purification process produces a new type of chiral Carbon Nanodots (CNDs). These CNDs are soluble in organic solvents, exhibit amino groups on their surface and display interesting absorption and emission properties along with mirror image profiles in the electronic circular dichroism spectrum. All these features set the stage for CNDs to act as multifunctional catalytic platforms, able to promote diverse chemical transformations. In particular, the outer shell composition of CNDs was instrumental to carry out organocatalytic reactions in an enantioselective fashion. In addition, the redox and light-absorbing properties of the material are suitable to drive photochemical processes. Finally, the photoredox and organocatalytic activations of CNDs were exploited at the same time to promote a cross-dehydrogenative coupling. This work demonstrates that CNDs can be used as catalysts to promote multiple reactivities, previously considered exclusive domain of molecular catalysts.

Phenanthrene-Extended Phenazine Dication: An Electrochromic Conformational Switch Presenting Dual Reactivity.

The synthesis and isolation of one of the few examples of a π-extended diamagnetic phenazine dication have been achieved by oxidizing a phenanthrene-based dihydrophenazine precursor. The resulting dication was isolated and fully characterized, highlighting an aromatic distorted structure, generated by the conformational change upon the oxidation of the dihydrophenazine precursor, which is also correlated with a marked electrochromic change in the UV-vis spectrum. The aromaticity of the dication has also been investigated theoretically, proving that the species is aromatic based on all major criteria (structural, magnetic, and energetic). Moreover, the material presents an intriguing dual reactivity, resulting in ring contraction to a π-extended triarylimidazolinium and reduction to the dihydrophenazine precursor, depending on the nature of the nucleophile involved. This result helps shed light on the yet largely unexplored reactivity and properties of extended dicationic polycyclic aromatic hydrocarbons (PAHs). In particular, the fact that the molecule can undergo a reversible change in conformation upon oxidation and reduction opens potential applications for this class of derivatives as molecular switches and actuators.

Amine-Rich Carbon Dots as Novel Nano-Aminocatalytic Platforms in Organic Synthesis.

The development of novel and effective metal-free catalytic systems, which can drive value-added organic transformations in environmentally benign solvents (for instance, water), is highly desirable. Moreover, these new catalysts need to be harmless, easy-to-prepare, and potentially recyclable. In this context, amine-rich carbon dots (CDs) have recently emerged as promising nano-catalytic platforms. These nitrogen-doped nanoparticles, which show dimensions smaller than 10 nm, generally consist of carbon cores that are surrounded by shells containing numerous amino groups. In recent years, organic chemists have used these surface amines to guide the design of several synthetic methodologies under mild operative conditions. This Concept highlights the recent advances in the synthesis of amine-rich carbon dots and their applications in organic catalysis, including forward-looking opportunities within this research field.

Nuclear Magnetic Resonance Reveals Molecular Species in Carbon Nanodot Samples Disclosing Flaws.

Carbon nanodots are currently one of the hot topics in the nanomaterials world, due to their accessible synthesis and promising features. However, the purification of these materials is still a critical aspect, especially for syntheses involving molecular precursors. Indeed, the presence of unreacted species or small organic molecules formed during solvothermal treatments can affect the properties of the synthesized nanomaterials. To illustrate the extreme importance of this issue, we present two case studies in which insufficient purification results in misleading conclusions regarding the chiral and fluorescent properties of the investigated materials. Key to identify molecular species is the use of nuclear magnetic resonance, which proves to be an effective tool. Our work highlights the need to include nuclear magnetic resonance as a standard characterization technique for carbon-based nanomaterials, to minimize the risk of observing properties that arise from molecular species, rather than the target carbon nanodots.

Turning the Light on Phenols: New Opportunities in Organic Synthesis.

Phenols (I) are extremely relevant chemical functionalities in natural, synthetic and industrial chemistry. Their corresponding electron-rich anions, namely phenolates (I), are characterized by interesting physicochemical properties that can be drastically altered upon light excitation. Specifically, phenolates (I) become strong reducing agents in the excited state and are able to generate reactive radicals from suitable precursors via single-electron transfer processes. Thus, these species can photochemically trigger strategic bond-forming reactions, including their direct aromatic C-H functionalization. Moreover, substituted phenolate anions can act as photocatalysts to enable synthetically useful organic transformations. An alternative mechanistic manifold is represented by the ability of phenolate derivatives I to form ground state electron donor-acceptor (EDA) complexes with electron-poor radical sources. These complementary scenarios have paved the way for the development of a wide range of relevant organic reactions. In this Minireview, we present the main examples of this research field, and give insight on emerging trends in phenols photocatalysis towards richer organic synthesis.

Synthesis of a novel tetra-phenol π-extended phenazine and its application as an organo-photocatalyst.

In this paper, the synthesis of a novel tetra-phenol π-extended dihydrophenazine is reported. The obtained derivative presents marked reducing properties in the excited state and was exploited as an organo-photocatalyst in dehalogenation and C-C bond formation reactions. These results underline the great potential of functionalized π-extended dihydrophenazines as organo-photocatalysts.

Diagnosis of PFAPA syndrome applied to a cohort of 17 adults with unexplained recurrent fevers.

BACKGROUND: The pathophysiology of PFAPA syndrome, mainly characterised by regularly recurring periodic fevers associated with aphthous stomatitis, pharyngitis and/or lymphadenitis, and mostly occurring in the paediatric setting, resembles an acquired autoinflammatory disease. The description of PFAPA syndrome in adult patients is largely increasing. OBJECTIVES: To recognise PFAPA syndrome in a group of adult patients evaluated for recurrent fevers in our Rheumatology Unit. METHODS: To apply current diagnostic criteria for PFAPA syndrome in a group of 359 adults with unexplained recurrent fevers monitored in our Unit between January 2007 and June 2011. RESULTS: We have found 17 out of 359 patients fulfilling the diagnosis of PFAPA syndrome: these patients (10 males, 7 females) were Caucasian with a mean age of 33.3±9.5 years, had recurrent febrile episodes begun at a mean age of 25.9±8.3 years and a mean number of episodes of 8.3±5.2 per year with a mean duration of 5.5±1.8 days. In particular, 7/17 patients had the 3 cardinal signs, the other 10 had a combination of 2 signs. Corticosteroids were given in 14/17 patients; tonsillectomy was performed in 9/17 patients: corticosteroid responsiveness and tonsillectomy efficacy were observed respectively in 11 and 2 patients. CONCLUSIONS: Our case highlights the importance of considering PFAPA syndrome in adults presenting with unexplained recurrent fevers and symptoms commonly encountered in general medical practice.

Parents' Perspective of Antibiotic Usage in Children: A Nationwide Survey in Italy.

BACKGROUND: Antibiotics represent the most widely prescribed drugs in children worldwide, both in hospital and community settings. A comprehensive approach to understanding the reasons and determinants of antibiotic prescription in the pediatric age is needed. This study aimed to assess parents' attitudes and perspectives about antibiotic use. METHODS: Prospective observational study was conducted in all Italian Regions between February 1 and April 30, 2020, using a standardized questionnaire. RESULTS: Six thousand six hundred twenty-five parents from all Italian regions completed the survey. Seventy-six percent of parents were aware that only bacteria are the target of antibiotics, but 92.9% knew that the antibiotic has no direct effect on fever. Antibiotic self-prescription (10.4%) or by remote consultation by phone call (19.9%) or message (9.6%) were relatively common. Ninety-three percent of parents were aware that excessive use of antibiotics could select resistant bacteria and 84.7% of them knew that they could actively fight antibiotic resistance. About two thirds of participants (66.1%) received information on antibiotic resistance from their family pediatrician. Parents born of Italy or those with lower income had a higher probability of having less information from pediatricians or knowledge of proper antibiotic use. DISCUSSION: Our study suggests that parents' knowledge and attitudes toward antibiotic use and prescription are improving compared with previous studies, while there is still a gap regarding antibiotic resistance, particularly on practices that can reduce its burden. Our study's negative finding is that families from low-income settings or those born abroad have significantly more misconceptions about important antibiotic practices.

Nutritional Status, Dietary Intake, and Adherence to the Mediterranean Diet of Children with Celiac Disease on a Gluten-Free Diet: A Case-Control Prospective Study.

The only effective treatment for celiac disease (CD) is a life-long strict gluten-free diet (GFD). Nutritional adequacy of the GFD has remained controversial and a matter of debate for a long time. No large case-control studies on children regarding the nutritional adequacy of the GFD has been performed. In this study, children diagnosed with CD on a GFD for ≥ 2 years were recruited. Controls were age and gender-matched healthy children not affected with CD. In both groups, anthropometric measurements and energy expenditure information were collected. Dietary assessment was performed by a 3-day food diary. Adherence to the Mediterranean diet was estimated by the KIDMED index. Overall, 120 children with CD and 100 healthy children were enrolled. No differences were found between CD children and controls in anthropometric measurements and energy expenditure. In the CD group, the daily intake of fats was significantly higher while the consumption of fiber was lower in comparison with the control group. The median KIDMED index was 6.5 in CD children and 6.8 in healthy controls. The diet of children with CD in this study was nutritionally less balanced than controls, with a higher intake of fat and a lower intake of fiber, highlighting the need for dietary counseling.